SEMICONDUCTING COMPOSITIONS COMPRISING SEMICONDUCTING POLYMERS

Abstract

A semiconducting composition comprising a semiconducting polymer and a semiconducting non-polymeric polycyclic compound, wherein the semiconducting polymer comprises units of A and/or B:

##STR00001##

wherein R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, x, y, p, q, r, R.sub.3, R.sub.4, R.sub.9, R.sub.10 and R.sub.11 have any of the meanings defined in the description.

Claims

1. A semiconducting composition comprising a semiconducting polymer and a semiconducting non-polymeric polycyclic compound, wherein the semiconducting polymer comprises units of A and/or B: ##STR00054## wherein R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are each independently selected from C.sub.1-C.sub.12 alkyl, C.sub.2-C.sub.12 alkenyl and aryl; wherein when any R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 group is C.sub.1-C.sub.12 alkyl or C.sub.2-C.sub.12 alkenyl, then each R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 group is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.12, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.12 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; wherein in the units A (when present) at least one of the R.sub.1 and R.sub.2 groups is substituted by one or more cyano groups and in the units B (when present) at least one of the R.sub.5, R.sub.6, R.sub.7 and R.sub.8 groups is substituted by one or more cyano groups; x represents 0, 1, 2 or 3; y represents 0, 1, 2 or 3; p represents 0, 1, 2 or 3; q represents 0, 1 or 2; r represents 0, 1, 2 or 3; wherein each R.sub.3, R.sub.4, R.sub.9, R.sub.10 and R.sub.11 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy.

2. A semiconducting composition according to claim 1, wherein the semiconducting polymer has a relative permittivity of greater than 3.4 at 1000 Hz.

3. A semiconducting composition according to claim 1, wherein the semiconducting polymer comprises at least 20%, monomeric A and/or B units.

4. A semiconducting composition according to claim 3, wherein the semiconducting polymer comprises at least 20%, monomeric A units.

5. A semiconducting composition according to claim 1, wherein the semiconducting polymer is a copolymer.

6. A semiconducting composition according to claim 5, wherein the semiconducting polymer is a copolymer comprising units of A and/or B and further comprising units of A, B, C, D and/or E: ##STR00055## wherein R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 are each independently selected from C.sub.1-C.sub.12 alkyl, C.sub.2-C.sub.12 alkenyl and aryl; wherein when any R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 group is C.sub.1-C.sub.12 alkyl or C.sub.2-C.sub.12 alkenyl, then each R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 group is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.28, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.28 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; x represents 0, 1, 2 or 3; y represents 0, 1, 2 or 3; p represents 0, 1, 2 or 3; q represents 0, 1 or 2; r represents 0, 1, 2 or 3; s represents 0, 1, 2 or 3; t represents 0, 1, 2 or 3; u represents 0, 1, 2 or 3; v represents 0, 1 or 2; w represents 0, 1, 2 or 3; g represents 0, 1, 2 or 3; h represents 0, 1, 2 or 3; i represents 0, 1, 2, 3 or 4; j represents 0, 1, 2, 3 or 4; wherein each R.sub.3, R.sub.4, R.sub.9, R.sub.10, R.sub.11, R.sub.15, R.sub.16, R.sub.21, R.sub.22, R.sub.23, R.sub.24, R.sub.25, R.sub.26 and R.sub.27 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy.

7. A semiconducting composition according to claim 6, wherein the semiconducting polymer is a copolymer comprising units of A and units of A, B, C, D and/or E.

8. A semiconducting composition according to claim 7, wherein the semiconducting polymer is a copolymer comprising units of A and units of A, units of A and units of B or units of A and units of C.

9. A semiconducting composition according to claim 8, wherein the semiconducting polymer is a copolymer comprising units of A and units of A, wherein R.sub.1 and R.sub.2 are each independently selected from C.sub.1-C.sub.12 alkyl, wherein the C.sub.1-C.sub.12 alkyl is optionally substituted by one or more substituents independently selected from cyano, hydroxyl, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and (OCH.sub.2CH.sub.2).sub.zOR.sub.12, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.12 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1 and/or R.sub.2 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; wherein at least one of the R.sub.1 and/or R.sub.2 groups is substituted by one or more cyano groups; wherein x represents 0, 1, 2 or 3 and y represents 0, 1, 2 or 3; wherein each R.sub.3 and R.sub.4 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy; wherein R.sub.1 and R.sub.2 are each independently selected from C.sub.1-C.sub.12 alkyl, wherein the C.sub.1-C.sub.12 alkyl is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.28, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.28 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1 and/or R.sub.2 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; wherein x represents 0, 1, 2 or 3 and y represents 0, 1, 2 or 3; and wherein each R.sub.3 and R.sub.4 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy.

10. A semiconducting composition according to claim 9, wherein R.sub.1 and R.sub.2 are each independently selected from C.sub.1-C.sub.12 alkyl, wherein the C.sub.1-C.sub.12 alkyl is substituted by one or more cyano groups; wherein x represents 0 and y represents 0; wherein R and R.sub.2 are each independently selected from C.sub.1-C.sub.12 alkyl, wherein the C.sub.1-C.sub.12 alkyl is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.28, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.28 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1 and/or R.sub.2 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; wherein x represents 0 and y represents 0.

11. A semiconducting composition according to claim 1, wherein the semiconducting polymer is: ##STR00056## wherein n and n are each an integer greater than 3 and wherein n and n may be the same or different and wherein m is an integer greater than 3.

12. A semiconducting layer comprising a semiconducting composition according to claim 1.

13. An electronic device comprising a semiconducting composition according to claim 1.

14. A semiconducting copolymer comprising units of A and/or B: ##STR00057## wherein R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are each independently selected from C.sub.1-C.sub.12 alkyl, C.sub.2-C.sub.12 alkenyl and aryl; wherein when any R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 group is C.sub.1-C.sub.12 alkyl or C.sub.2-C.sub.12 alkenyl, then each R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 group is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.12, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.12 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7 and/or R.sub.8 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; wherein in the units A (when present) at least one of the R.sub.1 and R.sub.2 groups is substituted by one or more cyano groups and in the units B (when present) at least one of the R.sub.5, R.sub.6, R.sub.7 and R.sub.8 groups is substituted by one or more cyano groups; x represents 0, 1, 2 or 3; y represents 0, 1, 2 or 3; p represents 0, 1, 2 or 3; q represents 0, 1 or 2; r represents 0, 1, 2 or 3; wherein each R.sub.3, R.sub.4, R.sub.9, R.sub.10 and R.sub.11 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy.

15. A semiconducting copolymer according to claim 14, further comprising units of A, B, C, D and/or E: ##STR00058## wherein R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 are each independently selected from C.sub.1-C.sub.12 alkyl, C.sub.2-C.sub.12 alkenyl and aryl; wherein when any R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 group is C.sub.1-C.sub.12 alkyl or C.sub.2-C.sub.12 alkenyl, then each R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 group is optionally substituted by one or more substituents independently selected from cyano, hydroxy, C.sub.1-C.sub.10 alkoxy, C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, aryl and a group of the formula (OCH.sub.2CH.sub.2).sub.zOR.sub.28, wherein z is 1, 2, 3, 4, 5 or 6 and R.sub.28 is C.sub.1-C.sub.4 alkyl; and wherein any aryl group present in R.sub.1, R.sub.2, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.13, R.sub.14, R.sub.17, R.sub.18, R.sub.19 and/or R.sub.20 is optionally substituted by one or more substituents independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, cyano, hydroxy, fluoro, chloro, trifluoromethyl and trifluoromethoxy; x represents 0, 1, 2 or 3; y represents 0, 1, 2 or 3; p represents 0, 1, 2 or 3; q represents 0, 1 or 2; r represents 0, 1, 2 or 3; s represents 0, 1, 2 or 3; t represents 0, 1, 2 or 3; u represents 0, 1, 2 or 3; v represents 0, 1 or 2; w represents 0, 1, 2 or 3; g represents 0, 1, 2 or 3; h represents 0, 1, 2 or 3; i represents 0, 1, 2, 3 or 4; j represents 0, 1, 2, 3 or 4; wherein each R.sub.3, R.sub.4, R.sub.9, R.sub.10, R.sub.11, R.sub.15, R.sub.16, R.sub.21, R.sub.22, R.sub.23, R.sub.24, R.sub.25, R.sub.26 and R.sub.27 (when present) is independently selected from C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.4 alkoxy.

16. A semiconducting copolymer according to claim 14, having a relative permittivity of greater than 3.4 at 1000 Hz.

17. A semiconducting copolymer according to claim 13, wherein the copolymer comprises at least 20%, monomeric A and/or B units.

18. A semiconducting copolymer according to claim 17, wherein the copolymer comprises at least 20%, monomeric A units.

19. A semiconducting copolymer according to claim 13, wherein the copolymer comprises units of A and further comprises units of A, B, C, D and/or E.

20. A semiconducting copolymer according to claim 19, wherein the copolymer comprises units of A and units of A, units of A and units of B or units of A and units of C.

21. A semiconducting copolymer according to claim 13, wherein the copolymer is: ##STR00059## wherein n and n are each an integer greater than 3 and wherein n and n may be the same or different.

22. A semiconducting composition comprising a semiconducting copolymer according to claim 14.

23. A semiconducting composition according to claim 22, further comprising a semiconducting non-polymeric polycyclic compound.

24. A semiconducting layer comprising a semiconducting composition according to claim 22.

25. An electronic device comprising a semiconducting composition according to claim 22.

26. Use of a semiconducting copolymer according to claim 14 as an organic binder in a semiconducting composition.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0530] For a better understanding of the invention, and to show how exemplary embodiments of the same may be carried into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which

[0531] FIG. 1 shows a transfer graph for Formulation Example 1(a) after 12 hours of dark storage.

[0532] The invention will be further discussed with reference to the following non-limiting Examples.

EXAMPLES

Method for the Measurement of the Relative Permittivity, .SUB.r .of the Polymers

[0533] The relative permittivity of each of the semiconducting polymers of Examples 1 to 6 was measured by fabricating capacitors according to the method detailed below.

[0534] 50 nm titanium bottom contact pads were prepared using sputter coating and standard photolithography and wet etching techniques. The semiconducting polymer of interest was then coated from solution, using a spin coater, to obtain a film thickness of typically between 200 nm and 500 nm. For capacitor fabrication, the polymer was coated as a 5% w/w solution in bromobenzene unless otherwise stated. Wherever possible two thicknesses were tested to ensure no variation of the relative permittivity result with thickness. The solvents used to dissolve the materials are shown below for each example. A top contact pad of approximately 50 nm aluminium was then deposited using shadow mask evaporation. The capacitance was measured using a calibrated Agilent Precision LCR meter E4980A set at a frequency of 1000 Hz. Film thickness measurements were performed using a Dektak surface profilometer. The area of overlap for the top and bottom contact pads, i.e. the area of the capacitor formed, was measured using a Zeiss stereo microscope equipped with image analysis software. Using these values the relative permittivity values were then calculated using the equation:

[00001]${\mathrm{.Math.}}_r=\frac{C.Math.d}{A.Math.{\mathrm{.Math.}}_0}$

where:
.sub.r is the relative permittivity of the semiconducting polymer
C is the measured capacitance of the capacitor
d is the thickness of the film of the semiconducting polymer
A is the area of the capacitor and
.sub.o is the permittivity of free space (a constant with a value of 8.85410.sup.12 F/m).

[0535] The capacitor array used contains 64 capacitors with areas of 0.11 cm.sup.2 and 0.06 cm.sup.2 respectively (32 of each size). The standard deviation for the value of relative permittivity on each array was calculated, which includes the standard deviation of capacitance, film thickness and area measurement combined.

Method a for Measurement of the Charge Mobility of the Semiconducting Polymers and of the Blends with Small Molecule Semiconductors

[0536] 10 cm square glass substrates (layer 01) (Corning Eagle XG) were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air. The substrates were then spin coated with a UV crosslinkable acrylate formulation PCAF01 (available from NeuDrive Ltd). After spin coating, the substrates were first placed on a hotplate at 95 C. for 1 minute to softbake, then UV flash exposed (1000 mJ) under a nitrogen blanket and post exposure baked at 115 C. for 10 minutes. The measured final thickness of the PCAF layer was measured to be 1 micron.

[0537] After the preparation of the PCAF01 sublayer the substrates were sputter coated with 50 nm of Au, then source and drain electrodes were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope and channel length features measured in several areas of the substrate.

[0538] Before proceeding with the organic thin-film transistor (OTFT) fabrication, the substrates were treated again in a Plasma Etch Inc. PE100 surface treatment system, using an Ar/O.sub.2 plasma. Each gas was supplied at a concentration of 50 sccm and a RF power of 250 W for 65 s.

[0539] Prior to spin coating of a semiconducting composition according to the invention, a 10 mM solution of 4-fluorothiophenol or 3-fluoro-4-methoxythiophenol (with 3-fluoro-4-methoxythiophenol being used in Example 1(a)) in 2-propanol was applied to the surface of the electrodes for 1 minute followed by spin coating and rinsing in 2-propanol (2 times), followed by drying on a hotplate. Unless otherwise stated, the OSC formulation was spin coated onto the SD electrodes using a Suss RC12 spinner set at 1500 rpm for 1 minute followed by baking on a hotplate for 60 seconds at 100 C. A solution of 1 part Cytop 809M (Asahi Glass) to 2 parts FC43 solvent (Acros Organics) was spin coated at 1500 rpm for 20 seconds and the sample was baked on a hotplate for 60 seconds at 100 C.

[0540] The substrates were then coated with 50 nm of Au by thermal evaporation and the gate electrodes were patterned as before with a combination of photolithography and wet etching.

Method B for Measurement of the Charge Mobility of the Semiconducting Polymers and of the Blends with Small Molecule Semiconductors

[0541] 10 cm square glass substrates (layer 01) (Corning Eagle XG) were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air. The substrates were then spin coated with a thermally crosslinkable polymer (P11) (available from NeuDrive Ltd). After spin coating, the substrates were first placed on a hotplate at 95 C. for 2 minutes to softbake, then baked at 150 C. for 60 minutes. The final thickness of the P11 layer was measured to be 1 micron.

[0542] After the preparation of the P11 sublayer the substrates were sputter coated with 50 nm of Au, then source and drain electrodes were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope and channel length features measured in several areas of the substrate.

[0543] Before proceeding with the organic thin-film transistor (OTFT) fabrication, the substrates were treated again in a Plasma Etch Inc. PE100 surface treatment system, using an Ar/O.sub.2 plasma. Each gas was supplied at a concentration of 50 sccm and a RF power of 250 W for 65 s.

[0544] Prior to spin coating of a semiconducting composition according to the invention, a 10 mM solution of 3-fluoro-4-methoxythiophenol in 2-propanol was applied to the surface of the electrodes for 1 minute followed by spin coating and rinsing in 2-propanol (2 times), followed by drying on a hotplate. Unless otherwise stated, the OSC formulation was spin coated onto the SD electrodes using a Suss RC12 spinner set at 1250 rpm for 1 minute followed by baking on a hotplate for 60 seconds at 100 C. A solution of 1 part Cytop 809M (Asahi Glass) to 2 parts FC43 solvent (Acros Organics) was spin coated at 1500 rpm for 20 seconds and the sample was baked on a hotplate for 60 seconds at 100 C.

[0545] The substrates were then coated with 50 nm of Au by thermal evaporation and the gate electrodes were patterned as before with a combination of photolithography and wet etching.

OTFT Characterisation

[0546] OTFTs were tested using a Wentworth Pegasus 300S semi-automated probe station in conjunction with a Keithley S4200 semiconductor parameter analyser. This allowed a statistically significant number of OTFT device measurements to be made on each substrate. The Keithley system calculated the linear mobility according to the equation shown below:

[00002]$=\frac{I_{\mathrm{DS}}}{V_{\mathrm{GS}}}.Math.\frac{L}{{\mathrm{WC}}_i.Math.V_{\mathrm{DS}}}$

where L is the transistor length, W is the transistor width, I.sub.ds is the drain to source current and C.sub.i is the dielectric capacitance per unit area. V.sub.DS (drain source voltage) was set at 2V unless otherwise stated, V.sub.GS (gate voltage) was varied from depletion to accumulation (typically +20V to 30V in 1V steps). The mobility values reported are an average of the 5 highest points in accumulation for each transistor. The data is reported for the channel lengths shown below and is displayed as an average of the devices measured. To exclude the small proportion of devices with gate leakage, a ratio of the gate current to the source-drain current was made at the highest V.sub.GS value for a V.sub.DS of 2V. If this ratio was below 10 (i.e. the gate current was more than 10% of the source drain current, then the device was excluded from the results). The standard deviation of the mobility values is reported as a percentage of the mean, and the number of devices measured is indicated in the results also. Turn on voltage of the transistors (V.sub.to) is defined as the gate voltage point at which the derivative of the logarithm of the drain current with respect to gate voltage is a maximum. It represents the transition point where the device starts to switch from the off state towards the on state. Turn on voltages close to 0V are preferred compared with higher turn on voltages, such as greater than +5V or +10V since this saves power in a display backplane driving scheme. In the device testing, since light absorption in the organic semiconductor layer can influence the V.sub.to of the transistors through the photo-generation of charge carriers, then the electrical tests were repeated after 12 hours of storage in the dark to determine the inherent V.sub.to for the devices, following the dissipation of the photogenerated charge in the devices.

Preparative Examples 1 to 6

[0547] NMR data was collected using instruments supplied by JEOL, specifically models ECX 300 and ECX 400.

[0548] Trace metal analysis for palladium (Pd) was performed using an Agilent 7700 ICP-MS in Spectrum Analysis (multi-tune) acquisition mode. Values are reported for the Pd content of the polymer in ppm and are indicative of the levels of Pd catalyst remaining after the synthetic procedure.

[0549] Unless otherwise stated, UPLC data was collected using a Waters Acquity UPLC system, using an XBridge BEH C18 2.5 m column and a gradient of 40-98% v/v acetonitrile in 10 mM ammonium bicarbonate (NH.sub.4HCO.sub.3) pH 10 over 1.2 minutes.

[0550] All solvents used were of HPLC grade, unless otherwise stated.

[0551] Silica gel purifications were carried out using Davisil 60 40-63 m, a product of Grace Davison Discovery Sciences, unless otherwise stated.

[0552] The number average molecular weight (M.sub.n) quoted in the Examples herein were determined by gel permeation chromatography (GPC) using a Hewlett Packard 1100 HPLC system with UV detection at a wavelength of 254 nm. Liquid chromatography data was processed using CIRRUS GPC Multi Detector Software, calibrated against polystyrene standards (supplied by Agilent). 13 calibration points were used with a molecular weight range 162-113300.

[0553] For convenience, the Examples herein which are polymers are identified by the substituent positions on the aromatic rings of their repeat units.

Example 1

Synthesis of the 30:70 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-dioctyl-9H-fluorene Random Copolymer

1(a) Synthesis of 9,9-dioctyl-9H-fluorene-2,7-diboronic Acid bis(pinacol) ester

[0554] ##STR00032##

[0555] 1,4-dioxane (666 mL) was charged to an argon purged 2 L 3-necked round bottom flask fitted with magnetic stirrer, thermometer and reflux condenser. The solvent was degassed with argon for 10 minutes, then 9,9-dioctyl-2,7-dibromofluorene (25 g, 0.0456 mol), bis(pinacolato)diboron (23.2 g, 0.0912 mol), potassium acetate (15.7 g, 0.16 mol) and palladium (II) chloride diphenylphosphinylferrocene (dppf) complex (1.7 g, 0.0023 mol) were added. The reaction mixture was heated at 100 C. for 18 hours, cooled to room temperature, and diluted with toluene (200 mL) and water (200 mL). After stirring for 10 minutes the mixture was filtered through a celite pad, washing with toluene. The filtrate layers were separated and the organic phase washed with water (2200 mL), then dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave a dark solid (31 g) which was refluxed with acetone (40 mL) for 5 minutes then cooled to 10 C. and filtered at the pump, washing with a small quantity of cold (10 C.) acetone. Drying in vacuo (50 C.) gave a brown solid (24.7 g). The part purified product was recrystallized from a mixture of acetonitrile (40 mL) and tetrahydrofuran (28 mL) to give, after isolation and drying in vacuo (50 C.), 9,9-dioctyl-9H-fluorene-2,7-diboronic acid bis(pinacol) ester as a pale beige solid (24.2 g, 83%).

[0556] .sup.1H NMR (400 MHz, CDCl.sub.3) 7.8 (d, 2H), 7.73 (s, 2H), 7.71 (d, 2H), 1.99 (m, 4H), 1.37 (s, 24H), 1.23-0.95 (m, 20H), 0.81 (t, 6H), 0.53 (m, 4H).

1(b) Synthesis of 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene

[0557] ##STR00033##

[0558] 2,7-dibromofluorene (7.97 g, 0.025 mol) was suspended in anhydrous DMSO (100 mL) in an argon purged 1 L, 3-necked round bottom flask fitted with magnetic stirrer, thermometer and reflux condenser. Sodium tert-butoxide (5.44 g, 0.0566 mol) was added portionwise at room temperature to produce a dark orange suspension. The reaction mixture was heated to 80 C. and 6-bromo-2,2-dimethylhexane nitrile (11.55 g, 9.65 mL, 0.0566 mol) was added dropwise over 15 minutes. The reaction mixture was heated at 80 C. for a further 10 minutes then cooled to room temperature and added to ice-water (200 mL) with stirring. The resulting mixture was extracted with ethyl acetate (2200 mL), then the combined organics washed with 1 M HCl (200 mL) and brine (200 mL), dried (MgSO.sub.4) and filtered. Concentration of the filtrates in vacuo gave the crude product which was purified by flash chromatography (gradient elution 10 to 20% v/v ethyl acetate in heptane). The product containing fractions were concentrated in vacuo then the residue triturated with methanol (60 mL). The resulting suspension was filtered at the pump washing with a small amount of cold (5 C.) methanol. Drying of the solid product gave 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene as an off white solid (12.05 g, 86%).

[0559] .sup.1H NMR (400 MHz, CDCl.sub.3) 7.51 (d, 2H), 7.47 (d, 2H), 7.43 (s, 2H), 1.98 (m, 4H), 1.24 (m, 20H), 0.57 (m, 4H).

[0560] UPLC Retention time 1.07 min (95.5%), m/z (MH.sup.+) 569.32.

Synthesis of the 30:70 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-dioctyl-9H-fluorene Random Copolymer (Example 1)

[0561] ##STR00034##

[0562] 1,4-dioxane (48 mL) and deionised water (DIW) (23 mL) were charged to an argon flushed 250 mL 3-necked round bottom flask, fitted with an overhead stirrer, a thermometer and a condenser. The solvents were degassed with argon for 30 minutes then 9,9-dioctyl-9H-fluorene-2,7-diboronic acid bis(pinacol) ester (3 g, 4.67 mmol), 2,7-dibromo-9,9-dioctyl-9H-fluorene (1.02 g, 1.87 mmol), 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene (1.6 g, 2.80 mmol) and tripotassium phosphate (K.sub.3PO.sub.4) (4.99 g, 23.34 mmol) were introduced. After degassing for a further 20 minutes, tris(dibenzylideneacetone)dipalladium(0) (4.3 mg, 0.0047 mmol) and tricyclohexylphosphine (3 mg, 0.01 mmol) were added and the reaction mixture was heated at 70 C. for 18 hours. After cooling to room temperature, reaction liquids were decanted and the residual solid dissolved in toluene (90 mL). The toluene solution was shaken with DIW (30 mL) and the biphasic mixture filtered through celite, washing with toluene. The layers were separated and the organic phase dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave a light green solid (3.74 g). The solid was dissolved in a 1:1 mixture of heptane and toluene, then purified by dry flash chromatography eluting sequentially with 1:1 heptane-toluene, toluene and 9:1 toluene-tetrahydrofuran. The product containing fractions were concentrated in vacuo to give a yellow foam (2.18 g), which was dissolved in toluene (200 mL) and treated with activated carbon (250 mg). The mixture was heated at 50 C. for 15 minutes, then filtered through a glass fibre membrane. The filtrate was treated with activated carbon a further five times in the same manner, then the filtrates were concentrated in vacuo to give a brown gum (2.03 g). The brown gum was dissolved in tetrahydrofuran (12 mL) and then added dropwise to vigorously stirred (500 rpm) methanol (40 mL) in a glass beaker. The resulting solids were collected at the pump and washed with 4:1 methanol-tetrahydrofuran (20 mL). Drying in vacuo gave the 30:70 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-dioctyl-9H-fluorene random copolymer as an off white solid (1.61 g). GPC M.sub.n 9029, PD 1.98.

[0563] The polymer of Example 1 had a relative permittivity of 4.16 at 1000 Hz, and a charge mobility of 2.5210.sup.4 cm.sup.2/Vs (formulated in absence of small molecule OSC as a 1% by weight tetralin solution, L=11.6 m). The average values for m and n in the polymer prepared, rounded to the nearest integer, were 7 and 16 respectively.

[0564] The trace metal content of the polymer of Example (1) was analysed by ICP-MS giving the following result: Pd content 16.8 ppm. This showed that the polymer contained very low levels of metal impurities.

Formulation Example 1(a)

[0565] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 1 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin and coated as an OSC layer in an OTFT device according to Method A described in the above procedure.

[0566] The OTFT performance of Formulation 1(a) is shown below:

TABLE-US-00001 Turn on voltage V.sub.to [V] Channel and value after dark storage Number of working length of Standard test shown in square brackets transistors tested OTFT Mobility deviation of (value shown is the median for on substrate Formulation [microns] cm.sup.2/Vs mobility, % the working devices tested) (out of 36) Polymer Example (1) 30:70 6.3 3.51 9.0 2.5 [1.5] 30 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,9- dioctyl-9H-fluorene random copolymer and TMTES in tetralin

[0567] Organic thin film transistors (OTFT) fabricated using Formulation 1(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity. V.sub.to values for devices fabricated using Formulation 1(a) are excellent, being only +1.5V for a channel length of 6 microns, as shown in FIG. 1.

Formulation Example 1(b)

[0568] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 1 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0569] The OTFT performance of Formulation 1(b) is shown below:

TABLE-US-00002 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (1) 30:70 7.8 2.87 11 36 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,9- dioctyl-9H-fluorene random copolymer and TMTES in tetralin/2- propanol mixed solvent

[0570] Organic thin film transistors (OTFT) fabricated using Formulation 1(b) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Formulation Example 1(c)

[0571] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 1 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0572] The OTFT performance of Formulation 1(c) is shown below:

TABLE-US-00003 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (1) 30:70 8.0 3.33 12 36 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,9- dioctyl-9H-fluorene random copolymer and TMTES in tetralin

[0573] Organic thin film transistors (OTFT) fabricated using Formulation 1(c) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Example 2

Synthesis of the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-dioctyl-9H-fluorene Alternating Copolymer

[0574] ##STR00035##

[0575] 1,4-dioxane (45 mL) and deionised water (DIW) (23 mL) were charged to an argon flushed 250 mL 3-necked round bottom flask, fitted with overhead stirrer, thermometer and condenser. The solvents were degassed with argon for 30 minutes then 9,9-dioctyl-9H-fluorene-2,7-diboronic acid bis(pinacol) ester (3 g, 4.67 mmol), 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene (2.66 g, 4.67 mmol) and tripotassium phosphate (K.sub.3PO.sub.4) (4.99 g, 23.34 mmol) were introduced. After degassing for a further 20 minutes, tris(dibenzylideneacetone)dipalladium(0) (4.3 mg, 0.0047 mmol) and tricyclohexylphosphine (3 mg, 0.01 mmol) were added and the reaction mixture was heated at 70 C. for 18 hours. After cooling to room temperature, the reaction mixture was worked up in identical manner to Example 1 above, providing a light green solid (3.78 g). The solid was dissolved in toluene, then purified by dry flash chromatography eluting sequentially with toluene and 9:1 toluene-tetrahydrofuran. The product containing fractions were concentrated in vacuo to give a green/yellow foam, which was dissolved in toluene (130 mL) and treated with activated carbon (160 mg). The mixture was heated at 50 C. for 15 minutes, then filtered through a glass fibre membrane. The filtrate was treated with activated carbon a further time in the same manner, then the filtrates were concentrated in vacuo to give a green solid. The brown gum was dissolved in tetrahydrofuran (10 mL) and then added dropwise to vigorously stirred (500 rpm) methanol (40 mL) in a glass beaker. The resulting solids were collected at the pump and washed with 4:1 methanol-tetrahydrofuran (10 mL). Drying in vacuo gave the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-dioctyl-9H-fluorene alternating copolymer as an off white solid (1.4 g). GPC M.sub.n 16471, PD 2.01.

[0576] The polymer of Example 2 had a relative permittivity of 5.16 at 1000 Hz and a charge mobility of 1.310.sup.4 cm.sup.2/Vs (formulated in absence of small molecule OSC as a 1% by weight tetralin solution, L=12.2 m). The average values for m and n in the polymer prepared, rounded to the nearest integer, were both 21.

Formulation Example 2(a)

[0577] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 2 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0578] The OTFT performance of Formulation 2(a) is shown below:

TABLE-US-00004 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (2) 50:50 7.8 3.07 11 34 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,9- dioctyl-9H-fluorene random copolymer and TMTES in tetralin/2- propanol mixed solvent

[0579] Organic thin film transistors (OTFT) fabricated using Formulation 2(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Example 3

Synthesis of the 50:50 9,9-bis(4-cyano-4-methylpentyl)fluorene:6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene Random Copolymer

3(a) Synthesis of 5-chloro-2,2-dimethylpentanenitrile

[0580] ##STR00036##

[0581] Diisopropylamine (23.7 mL, 0.17 mol) was added to anhydrous tetrahydrofuran (70 mL) and cooled to 70 C. under argon atmosphere. n-butyl lithium (2.1 M in hexane, 77 mL, 0.16 mol) was added dropwise. After cooling back to 70 C., a solution of isobutyronitrile (9.5 mL, 0.11 mol) in anhydrous THF (35 mL) was added dropwise to give a yellow solution, then stirred at 70 C. for 20 min. A solution of 1-chloro-3-bromopropane (25 g, 0.16 mol) in anhydrous THF (35 mL) was added dropwise at 70 C. and the reaction mass stirred for a further 30 min. The reaction was quenched with saturated aqueous ammonium chloride and allowed to warm to room temperature. Heptane was added, the layers split and the aqueous phase extracted with further heptane (2). The combined organics were dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave an orange oil, which was purified by dry flash chromatography (0 to 10% ethyl acetate in heptane) to give 5-chloro-2,2-dimethylpentanenitrile as a colourless oil (10 g, 43%).

[0582] .sup.1H NMR (300 MHz, CDCl.sub.3) 3.54 (t, 2H), 1.92 (m, 2H), 1.65 (m, 2H), 1.31 (s, 6H).

3(b) Synthesis of 5-iodo-2,2-dimethylpentanenitrile

[0583] ##STR00037##

[0584] 5-chloro-2,2-dimethylpentanenitrile (Example 3(a)) (10 g, 0.069 mol) was dissolved in methyl ethyl ketone (100 mL). Sodium iodide (13.4 g, 0.089 mol) was added and the mixture heated at reflux for 18 hours. After cooling to room temperature, the solids were filtered off and washed with heptane. The filtrates were concentrated in vacuo then triturated with heptane. The solids were filtered and washed again with heptane, then the combined heptane layers concentrated in vacuo. The residue was taken up in ethyl acetate and washed with 10% w/w sodium thiosulfate followed by brine. The organic layer was dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave 5-iodo-2,2-dimethylpentanenitrile as a yellow oil (14.3 g, 87%).

[0585] .sup.1H NMR (300 MHz, CDCl.sub.3) 3.20 (t, 2H), 2.02 (m, 2H), 1.63 (m, 2H), 1.35 (s, 6H).

3(c) Synthesis of 2,7-dibromo-9,9-bis(4-cyano-4-methylpentyl)fluorene

[0586] ##STR00038##

[0587] 2,7-dibromofluorene (Sigma Aldrich) (6.4 g, 0.02 mol) was dissolved 1 h anhydrous tetrahydrofuran (70 mL) under argon atmosphere. Sodium tert-butoxide (4.3 g, 0.044 mol) was added portionwise to give a deep red solution, which was stirred for 20 minutes at room temperature. A solution of 5-iodo-2,2-dimethylpentanenitrile (Example 3(b)) (10.5 g, 0.044 mol) in anhydrous tetrahydrofuran (25 mL) was added dropwise, then the reaction mixture stirred at room temperature overnight. The following day, ethyl acetate and water were added and the layers separated. The aqueous phase was extracted with ethyl acetate (2). The combined organics were dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave an orange oil, which was purified by dry flash chromatography (5 to 20% ethyl acetate in heptane) to give an orange oil. The sample was purified a second time by dry flash chromatography (elution as above) then recrystallised from heptane to give 2,7-dibromo-9,9-bis(4-cyano-4-methylpentyl)fluorene as a yellow solid (6.06 g, 56%).

[0588] .sup.1H NMR (300 MHz, CDCl.sub.3) 7.56-7.45 (m, 6H), 2.01 (t, 4H), 1.28 (m, 4H), 1.11 (s, 12H), 0.80 (m, 4H).

3(d) Synthesis of 2,2-(6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene-2,8-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)

[0589] ##STR00039##

[0590] A round bottom flask was charged with 2,8-dibromo-6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene (8.84 g, Sigma-Aldrich), potassium acetate (3.53 g, Alfa-Aesar) and bis(pinacolato)diboron (5.74 g, Allychem) in dioxane (220 mL). The mixture was degassed for 15 minutes then [1,1-bis(diphenylphosphino)ferrocene]-dichloropalladium (II) (419 mg, Peakdale) was added and the reaction mixture heated to 100 C. for 18 hours. The mixture was concentrated and the residue was taken up in DCM/water (2:1) and filtered through a pad of celite washing with DCM. The organic layer was washed with brine, dried (MgSO.sub.4) and concentrated onto silica. Purification by dry flash column eluting with heptane/ethyl acetate mixtures gave a yellow solid which was recrystallised from THF/MeCN to give 2,2-(6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene-2,8-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) as a yellow solid (5.92 g, 60%).

[0591] .sup.1H NMR (400 MHz, CDCl.sub.3) 7.83 (m, 2H), 7.73 (m, 4H), 7.62 (s, 2H), 1.91-2.12 (br m, 8H), 1.39 (s, 24H), 0.91-1.22 (br m, 40H), 0.79 (m, 12H), 0.50-0.70 (br m, 8H).

Synthesis of the 50:50 9,9-bis(4-cyano-4-methylpentyl)fluorene:6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene Random Copolymer (Example 3)

[0592] ##STR00040##

[0593] A mixture of 1,4-dioxane (134 mL) and water (66 mL) was degassed with argon for 20 minutes. 2,7-dibromo-9,9-bis(4-cyano-4-methylpentyl)fluorene (Example 3(c)) (5.08 g, 9.4 mmol), 2,2-(6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene-2,8-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (Example 3(d)) (8.95 g, 9.4 mmol) and tripotassium phosphate (9.94 g, 47 mmol) were added, followed by tris(dibenzylideneacetone)dipalladium(0) (9 mg, 0.0094 mmol) and tricyclohexylphosphine (6 mg, 0.022 mmol). The reaction mixture was heated at 70 C. for 18 hours. After cooling to room temperature, a solid mass formed. The reaction liquids were decanted and the residual solid dissolved in toluene (300 mL), then the solution was stirred with deionized water (150 mL) and filtered through a celite pad washing with toluene. The filtrate layers were separated and the organic phase washed with deionized water (200 mL). Concentration of the organic phase in vacuo gave a dark green oil, which was purified by dry flash chromatography (toluene) to give a dark yellow foam. This material was dissolved in toluene (200 mL) and activated charcoal (1 g) was added, then the mixture heated at 50 C. and filtered hot. The activated charcoal treatment and filtration was repeated three times in total, then the filtrate was concentrated in vacuo to give a yellow foam (8 g). The material was dissolved in tetrahydrofuran (75 mL) and added dropwise to stirred methanol (250 mL). After 45 minutes of stirring, the liquids were decanted off and the solids dried to give the 50:50 9,9-bis(4-cyano-4-methylpentyl)fluorene:6,6,12,12-tetraoctyl-6,12-dihydroindeno[1,2-b]fluorene random copolymer as a pale yellow powder (6.8 g). GPC M.sub.n 5143, PD 2.12.

[0594] The polymer of Example 3 had a relative permittivity of 6.0 at 1000 Hz, and a charge mobility of 2.310.sup.4 cm.sup.2Ns (formulated in absence of small molecule OSC as a 2% by weight tetralin solution, L=10.5 m). The average values for m and n in the polymer prepared, rounded to the nearest integer, were 5 and 5 respectively.

Formulation Example 3(a)

[0595] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 3 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in a tetralin and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0596] The OTFT performance of Formulation 3(a) is shown below:

TABLE-US-00005 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (3) 50:50 8.0 1.47 16 36 9,9-bis(4-cyano-4- methylpentyl)fluorene:6,6,12,12- tetraoctyl-6,12- dihydroindeno[1,2-b]fluorene random copolymer and TMTES in tetralin/2- propanol mixed solvent

[0597] Organic thin film transistors (OTFT) fabricated using Formulation 3(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Example 4

Synthesis of the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene Random Copolymer

4(a) Synthesis of 2,7-dibromo-9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene

[0598] ##STR00041##

[0599] 2,7-dibromofluorene (Sigma Aldrich) (15.7 g, 0.048 mol) was dissolved in anhydrous tetrahydrofuran (150 mL) and cooled to 5 C. under argon atmosphere. Sodium tert-butoxide (10.5 g, 0.109 mol) was added portionwise, giving a deep red colour. After completion of addition, the reaction mixture was stirred at room temperature for 20 minutes. A solution of 1-bromo-2-(2-methoxyethoxy)ethane (Sigma Aldrich) (20 g, 0.109 mol) in anhydrous THF (50 mL) was added dropwise. The solution turned dark purple and an exotherm to 30 C. was observed. The reaction mixture was stirred at room temperature for 72 hours then diluted with water and ethyl acetate. The layers were separated and the aqueous phase extracted with ethyl acetate (2). The combined organic layers were washed with water and brine then dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo followed by purification of the residue by dry flash chromatography (0 to 40% ethyl acetate in heptane) gave 2,7-dibromo-9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene as a yellow oil (10 g, 40%).

[0600] .sup.1H NMR (300 MHz, CDCl.sub.3) 7.52-7.42 (m, 6H), 3.27 (m, 10H), 3.16 (m, 4H), 2.76 (m, 4H), 2.34 (m, 4H).

4(b) Synthesis of 9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene-2,7-diboronic Acid bis(pinacol) ester

[0601] ##STR00042##

[0602] 2,7-dibromo-9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene (Example 4(a)) (10 g, 0.019 mol) was dissolved in 1,4-dioxane (220 mL) and the solution degassed with argon while stirring. Bis(pinacolato)diboron (10.6 g, 0.042 mol), potassium acetate (6.5 g, 0.066 mol) and palladium (II) chloride diphenylphosphinylferrocene (dppf) complex (0.693 g, 0.0009 mol) were added, and the reaction mixture was heated at 100 C. for 18 hours. After cooling to room temperature, the reaction mixture was filtered through a celite pad then the filtrate concentrated in vacuo to give a sticky black solid. The solid was triturated with isopropanol (15 mL) to give a suspension, then the solids collected at the pump and washed with isopropanol (310 mL). Drying gave a beige solid which was recrystallised from isopropanol to give 9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene-2,7-diboronic acid bis(pinacol) ester as a beige solid (6.7 g, 57%).

[0603] .sup.1H NMR (300 MHz, CDCl.sub.3) 7.85 (s, 2H), 7.80 (m, 2H), 7.70 (m, 2H), 3.30-3.26 (m, 10H), 3.15 (m, 4H), 2.67 (m, 4H), 2.44 (m, 4H).

Synthesis of the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene Random Copolymer (Example 4)

[0604] ##STR00043##

[0605] A mixture of 1,4-dioxane (66 mL) and deionised water (33 mL) was degassed with argon for 1 hour. 9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene-2,7-diboronic acid bis(pinacol) ester (Example 4(b)) (4 g, 0.0064 mol), 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene (Example 1(b)) (3.7 g, 0.0064 mol) and tripotassium phosphate (17.5 g, 0.083 mol) were added and the resulting mixture warmed to 50 C. while continuing argon degassing. Tris(dibenzylideneacetone)dipalladium(0) (15 mg, 0.016 mmol) and tricyclohexylphosphine (10 mg, 0.04 mmol) were added, and the reaction mixture was heated at 70 C. for 18 hours, during this time a solid polymer mass formed. The reaction was cooled to room temperature and the liquids decanted. The solid was then stirred with toluene (200 mL) at room temperature for 18 hours. A thick gel formed. The mixture was concentrated in vacuo, then tetrahydrofuran (500 mL) was added to the residue and heated at 60 C. with stirring. The tetrahydrofuran solution was decanted. This warm extraction process was repeated (3) and the tetrahydrofuran extracts combined, then concentrated in vacuo to give a plastic-like solid. The solid was redissolved in tetrahydrofuran then passed through a celite pad, eluting with tetrahydrofuran. The product eluate was partially concentrated, then rediluted to ca 300 mL total volume with tetrahydrofuran. Activated charcoal (1 g) was added. The mixture was heated at 50 C. for 30 minutes and filtered while hot. The activated charcoal treatment and filtration was repeated three times in total, then the filtrate was concentrated in vacuo to give a yellow foam. The foam was redissolved in tetrahydrofuran (75 mL) then added dropwise to rapidly stirred methanol (250 mL) in a glass beaker. The resulting solids were collected by vacuum filtration and air dried (50 C.) to give the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,9-Bis[2-(2-methoxyethoxy)ethyl]-9H-fluorene random copolymer as a yellow solid (1.27 g). GPC M.sub.n 45783, PD 4.50.

[0606] The polymer of Example 4 had a relative permittivity of 5.9 at 1000 Hz, and a charge mobility of 6.210.sup.7 cm.sup.2/Vs (formulated in absence of small molecule OSC as a 1% by weight bromobenzene solution, L=12.2 m). The average values for m and n in the polymer prepared, rounded to the nearest integer, were 58 and 58 respectively.

Formulation Example 4(a)

[0607] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 4 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in a bromobenzene and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0608] The OTFT performance of Formulation 4(a) is shown below:

TABLE-US-00006 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (4) 50:50 7.4 2.28 11 35 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,9- Bis[2-(2-methoxyethoxy)ethyl]- 9H-fluorene random copolymer and TMTES in bromobenzene/2- propanol mixed solvent

[0609] Organic thin film transistors (OTFT) fabricated using Formulation 4(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Example 5

Synthesis of the 9-hexyl-9-(5-cyano-5-methylhexyl))fluorene homopolymer 5(a) Synthesis of 6-chloro-2,2-dimethylhexanenitrile

[0610] ##STR00044##

[0611] Diisopropylamine (31.4 g, 0.31 mol) was added to anhydrous tetrahydrofuran (140 mL) and cooled to 70 C. under argon atmosphere. n-butyl lithium (2.1 M in hexane, 138 mL, 0.29 mol) was added dropwise maintaining T<60 C. using external cooling. After cooling back to 70 C., a solution of isobutyronitrile (13.5 g, 0.19 mol) in anhydrous THF (70 mL) was added dropwise and the reaction mixture stirred at 70 C. for 20 min. A solution of 1-chloro-4-bromobutane (50 g, 0.29 mol) in anhydrous THF (70 mL) was added dropwise at 70 C. and the reaction mass stirred for a further 2.5 hours. The reaction was quenched with saturated aqueous ammonium chloride (150 mL) and allowed to warm to room temperature. Heptane was added, the layers split and the aqueous phase extracted with further heptane (2). The combined organics were washed with brine, dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrates in vacuo gave a pale yellow oil, which was purified by dry flash chromatography (0 to 10% ethyl acetate in heptane) to give 6-chloro-2,2-dimethylhexanenitrile as a colourless oil (28 g, 92%).

[0612] .sup.1H NMR (300 MHz, CDCl.sub.3) 3.54 (t, 2H), 1.80 (m, 2H), 1.62 (m, 2H), 1.52 (m, 2H), 1.32 (s, 6H).

5(b) Synthesis of 6-iodo-2,2-dimethylhexanenitrile

[0613] ##STR00045##

[0614] 6-chloro-2,2-dimethylhexanenitrile (28 g, 0.18 mol) was dissolved in methyl ethyl ketone (300 mL). Sodium iodide (34.2 g, 0.23 mol) was added and the mixture heated at reflux for 18 hours. After cooling to room temperature, the solids were filtered off and washed with heptane. The filtrates were concentrated in vacuo then triturated with heptane. The solids were filtered and washed again with heptane, then the combined heptane layers concentrated in vacuo to give 6-iodo-2,2-dimethylhexanenitrile as a yellow oil (43.8 g, 97%).

[0615] .sup.1H NMR (300 MHz, CDCl.sub.3) 3.16 (t, 2H), 1.80 (m, 2H), 1.62-1.46 (m, 4H), 1.31 (s, 6H).

5(c) Synthesis of 9-hexyl-9-(5-cyano-5-methylhexyl)fluorene

[0616] ##STR00046##

[0617] Fluorene (Sigma Aldrich) (10 g, 0.06 mol) was dissolved in anhydrous tetrahydrofuran (150 mL) and cooled to 70 C. under argon atmosphere. n-butyl lithium (2.5 M in hexane, 24 mL, 0.06 mol) was added dropwise to give an orange suspension, then the reaction mixture warmed to 10 C. and stirred for 1 hour. The reaction mixture was cooled back to 70 C., then 1-bromohexane (9.93 g, 0.06 mol) was added dropwise. The reaction mixture was allowed to warm to room temperature and stirred for 2 hours while maintaining argon atmosphere, then cooled back to 70 C. n-butyl lithium (2.5 M in hexane, 24 mL, 0.06 mol) was added dropwise to give a red solution. The reaction mixture was warmed to 10 C. and stirred for 1 hour, then cooled back to 70 C. before dropwise addition of 6-iodo-2,2-dimethylhexane nitrile (Example 5(a)) (15.1 g, 0.06 mol). The reaction mixture was stirred at room temperature for 18 hours, then cooled to 5 C. and quenched with water (150 mL). The layers were separated and the aqueous phased extracted with ethyl acetate (200 mL). The combined organics were washed with water (200 mL) and brine (200 mL), dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrate in vacuo gave an orange oil, which was partially purified by dry flash chromatography (0 to 10% ethyl acetate in heptane). The product containing fractions were concentrated in vacuo and repurified by dry flash chromatography using a narrower gradient (0 to 5% ethyl acetate in heptane). Pure column fractions were concentrated in vacuo to give 9-hexyl-9-(5-cyano-5-methylhexyl)fluorene as a solidifying off white oil (3.4 g, 15%).

[0618] .sup.1H NMR (300 MHz, CDCl.sub.3) 7.70 (m, 2H), 7.37-7.30 (m, 6H), 2.04 (m, 4H), 1.28 (m, 10H), 1.12-1.04 (m, 6H), 0.79 (t, 3H), 0.64 (m, 4H).

Synthesis of the 9-hexyl-9-(5-cyano-5-methylhexyl))fluorene homopolymer (Example 5)

[0619] ##STR00047##

[0620] Anhydrous iron (III) chloride (5.9 g, 0.036 mol) was suspended in dichloromethane (80 mL) and cooled to 0 C. under argon atmosphere, with stirring. 9-hexyl-9-(5-cyano-5-methylhexyl)fluorene (Example 5(b)) (3.4 g, 0.009 mol) was dissolved in dichloromethane (20 mL) and added dropwise. A black suspension formed. The reaction mixture was stirred at room temperature for 96 hours, then poured into vigorously stirred methanol (200 mL). The solids were collected by vacuum filtration, then redissolved in toluene (200 mL). Deionised water (150 mL) was added then the mixture filtered through a celite pad, rinsing with toluene and deionised water. The layers were separated and the organic phase concentrated in vacuo to give a yellow solid. The solid was redissolved in toluene (80 mL) and activated charcoal (1 g) was added. The mixture was heated at 50 C. for 30 minutes and filtered while hot. The activated charcoal treatment and filtration was repeated three times in total, then the filtrate was concentrated in vacuo to give a yellow solid. The foam was redissolved in tetrahydrofuran (45 mL) then added dropwise to rapidly stirred methanol (150 mL) in a glass beaker. The resulting solids were collected by vacuum filtration and air dried (50 C.) to give 9-hexyl-9-(5-cyano-5-methylhexyl)fluorene homopolymer as a yellow solid (1.77 g). GPC M.sub.n 12276, PD 2.86.

[0621] The polymer of Example 5 had a relative permittivity of 6.2 at 1000 Hz, and a charge mobility of 1.010.sup.5 cm.sup.2/Vs (formulated in absence of small molecule OSC as a 2% by weight tetralin solution, L=10.5 m). The average value for m in the polymer prepared, rounded to the nearest integer, was 33.

Formulation Example 5(a)

[0622] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 5 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin solvent and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0623] The OTFT performance of Formulation 5(a) is shown below:

TABLE-US-00007 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (5) 9- 8.3 3.72 10 36 hexyl-9-(5-cyano-5- methylhexyl))fluorene homopolymer and TMTES in tetralin/2-propanol mixed solvent

[0624] Organic thin film transistors (OTFT) fabricated using Formulation 5(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Formulation Example 5(b)

[0625] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 5 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in tetralin solvent and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0626] The OTFT performance of Formulation 5(b) is shown below:

TABLE-US-00008 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (5) 9- 8.1 2.53 19 20 hexyl-9-(5-cyano-5- methylhexyl))fluorene homopolymer and TMTES in tetralin

[0627] Organic thin film transistors (OTFT) fabricated using Formulation 5(b) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Example 6

Synthesis of the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene 9,10-dioctylphenanthrene Random Copolymer

6(a) Synthesis of 4,4-dibromo-2-biphenylcarboxylic Acid

[0628] ##STR00048##

[0629] 2,7-dibromofluorenone (Sigma Aldrich] (28.4 g, 0.069 mol), potassium hydroxide (39 g, 0.69 mol) and toluene (470 mL) were combined and heated at reflux with stirring for 4 hours. The reaction mass was cooled to room temperature, diluted with water (1 L) and toluene (500 mL) and briefly stirred. The layers were separated and the organic phase washed with water (300 mL). The toluene phase was discarded. The combined aqueous layers were acidified with 2 M hydrochloric acid and a white precipitate formed. After stirring for 15 minutes, the solids were collected by vacuum filtration and washed with water, then air dried (50 C.) to constant weight. This gave 4,4-dibromo-2-biphenylcarboxylic acid as a white solid (23.1 g, 94%).

[0630] .sup.1H NMR (d.sub.6 DMSO) 7.87 (d, 1H), 7.75 (dd, 1H), 7.59 (2H, d), 7.32-7.23 (m, 3H).

6(b) Synthesis of 4,4-Dibromo-2-biphenylcarboxylic Acid Chloride

[0631] ##STR00049##

[0632] 4,4-dibromo-2-biphenylcarboxylic acid (Example 6(a)) (23.2 g, 0.065 mol) was suspended in dichloromethane (230 mL) under an argon atmosphere. Oxalyl chloride (11 mL, 0.13 mol) was added followed by N,N-dimethylformamide (1-2 drops). The reaction mixture was stirred at room temperature for 18 hours (gas evolution) and an orange solution formed. The reaction mixture was concentrated in vacuo to give an orange solid, which was recrystallised from heptane. Prior to cooling and crystallisation the hot heptane solution containing the product was decanted to remove a small amount of non soluble residue. After cooling the heptane solution, the solid product was collected by vacuum filtration and dried under vacuum (40 C.). This gave 4,4-dibromo-2-biphenylcarboxylic acid chloride as a light brown solid (20.9 g, 86%).

[0633] .sup.1H NMR (300 MHz, CDCl.sub.3) 8.13 (d, 1H), 7.74 (dd, 1H), 7.55 (m, 2H), 7.24 (d, 1H), 7.16 (m, 2H).

6(c) Synthesis of 9-octadecyne

[0634] ##STR00050##

[0635] 1-decyne (15 g, 0.108 mol) was dissolved in anhydrous tetrahydrofuran (250 mL) and cooled to 78 C. under argon. n-butyl lithium (2.5 M in hexane, 39.2 mL, 0.098 mol) was added dropwise, maintaining the reaction temperature <60 C., and the mixture was then stirred at 78 C. for 30 minutes before warming to room temperature. n-octyl bromide (15 mL, 0.087 mol) and sodium iodide (1.62 g, 0.0087 mol) were added, and the reaction mixture heated at reflux for 18 hours. After cooling to 0 C., the reaction was quenched by addition of saturated ammonium chloride solution. The mixture was diluted with water (50 mL) and ethyl acetate (200 mL). The layers were separated and the aqueous phase extracted with ethyl acetate (2). The combined organics were washed with water (200 mL), brine (200 mL) then dried (Na.sub.2SO.sub.4) and filtered. Concentration of the filtrate in vacuo gave 9-octadecyne as an orange oil (25.1 g, 93%).

[0636] .sup.1H NMR (300 MHz, CDCl.sub.3) 2.18-2.10 (m, 4H), 1.55-1.15 (m, 24H), 0.85 (m, 6H).

6(d) Synthesis of 2,7-dibromo-9,10-dioctylphenanthrene

[0637] ##STR00051##

Note: Xylenes (Mixture of Isomers) was Thoroughly Degassed with Argon Prior to Use.

[0638] 4,4-dibromo-2-biphenylcarboxylic acid chloride (Example 6(b)) (6.7 g, 0.018 mol) and 9-octadecyne (Example 6(c)) (5.3 g, 0.021 mol) were dissolved in xylenes (40 mL) to prepare Solution A. In a round bottom flask, 1,5-cyclooctadiene iridium(I) chloride dimer (0.12 g, 0.00018 mol) was dissolved in xylenes (180 mL). Tri(tert-butyl phosphine) (1 M in toluene, 0.36 mL, 0.00036 mol) was added, followed by Solution A. The reaction mixture was heated at 130 C. for 18 hours to give a dark orange solution. After cooling to room temperature, the reaction mixture was concentrated in vacuo to give a black solid. The solid was triturated with isopropanol and stirred at room temperature for 1 hour. The solids were collected by vacuum filtration, washed with isopropanol (2) and partially dried. Recrystallisation of the partially purified solid from isopropanol gave 2,7-dibromo-9,10-dioctylphenanthrene as an off white solid (5.2 g, 52%).

[0639] .sup.1H NMR (300 MHz, CDCl.sub.3) 8.49 (d, 2H), 8.19 (m, 2H), 7.66 (m, 2H), 3.06 (m, 4H), 1.69-1.51 (m, 10H), 1.42-1.32 (m, 14H), 0.90 (m, 6H).

6(e) Synthesis of 9,10-dioctylphenanthrene-2,7-diboronic Acid bis(pinacol) ester

[0640] ##STR00052##

[0641] 2,7-dibromo-9,10-dioctylphenanthrene (Example 6(d)) (10.2 g, 0.018 mol) was dissolved in 1,4-dioxane (220 mL) and the solution degassed with argon for 30 minutes. Bis(pinacolato)diboron (10.2 g, 0.04 mol), potassium acetate (6.3 g, 0.064 mol) and palladium (II) chloride diphenylphosphinylferrocene (dppf) complex (0.666 g, 0.0009 mol) were added, and the reaction mixture was heated at 90-100 C. for 18 hours. At this stage thin layer chromatography (TLC) analysis showed a small amount of starting material remaining, and the reaction mixture was heated at 90-100 C. for a further 3 hours. After cooling to room temperature, the reaction mixture was filtered through a celite pad washing with dichloromethane, then the filtrate was concentrated in vacuo to give a dark solid. Recrystallisation from isopropanol gave 9,10-dioctylphenanthrene-2,7-diboronic acid bis(pinacol) ester as a brown solid (8.6 g, 73%)

[0642] .sup.1H NMR (300 MHz, CDCl.sub.3) 8.70 (d, 2H), 8.59 (s, 2H), 7.96 (d, 2H), 3.22 (m, 4H), 1.77-1.67 (m, 4H), 1.63-1.53 (m, 4H), 1.48-1.27 (m, 40H), 0.90 (6H, m).

Synthesis of the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene 9,10-dioctylphenanthrene Random Copolymer (Example 6)

[0643] ##STR00053##

[0644] A mixture of 1,4-dioxane (110 mL) and deionized water (50 mL) was degassed with argon. 2,7-dibromo-9,9-bis(5-cyano-5-methylhexyl)fluorene (Example 1(b)) (4.36 g, 0.0076 mol), 9,10-dioctylphenanthrene-2,7-diboronic acid bis(pinacol) ester (Example 6(e)) (5 g, 0.0076 mol) and tripotassium phosphate (8.1 g, 0.038 mol) were added and the resulting solution degassed again with argon. Tris(dibenzylideneacetone)dipalladium(0) (7 mg, 0.0076 mmol) and tricyclohexylphosphine (5 mg, 0.018 mmol) were added, and the reaction mass was heated at 70 C. for 18 hours. Formation of a green solid mass was observed. After cooling to room temperature, the liquids were decanted and the solid mass was dissolved in toluene (300 mL). Deionised water (200 mL) was added and the mixture filtered through a celite pad, washing through with toluene. The layers were separated and the organic phase was washed with deionised water (200 mL), then concentrated in vacuo. The crude product was redissolved in toluene, then purified by dry flash chromatography eluting first with toluene and then with 1:1 tetrahydrofuran-toluene. The product containing fractions were combined and concentrated in vacuo to give a dark green solid. The solid was redissolved in toluene (250 mL). Activated charcoal (1 g) was added, then the mixture heated at 50 C. for 30 minutes and filtered while hot. The activated charcoal treatment and filtration was repeated three times in total, then the filtrate was concentrated in vacuo and redissolved in tetrahydrofuran (75 mL). This solution was added dropwise to stirred methanol (250 mL). After 45 minutes of stirring, the solids were filtered at the pump then air dried (50 C.) to give the 50:50 9,9-bis(5-cyano-5-methylhexyl)fluorene:9,10-dioctylphenanthrene random copolymer (4.52 g) as a green solid. GPC M.sub.n 9241, PD 2.07.

[0645] The polymer of Example 6 had a relative permittivity of 7.3 at 1000 Hz, and a charge mobility of 1.410.sup.5 cm.sup.2/Vs (formulated in absence of small molecule OSC as a 2% by weight bromobenzene solution, L=10.5 m). The average values for m and n in the polymer prepared, rounded to the nearest integer, were 11 and 11 respectively.

Formulation Example 6(a)

[0646] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 6 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in bromobenzene solvent and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0647] The OTFT performance of Formulation 6(a) is shown below:

TABLE-US-00009 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (6) 50:50 7.9 2.14 21 35 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,10- dioctylphenanthrene random copolymer and TMTES in bromobenzene

[0648] Organic thin film transistors (OTFT) fabricated using Formulation 6(a) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.

Formulation Example 6(b)

[0649] In these Examples the ratio of polymer to the semiconductor is in parts by weight. The polymer of Example 6 was formulated with 1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES) in a ratio 2:1 at a total solids loading of 1.2% by weight in bromobenzene solvent and 2-propanol mixed solvent (ratio 9:1 by weight) and coated as an OSC layer in an OTFT device according to Method B described in the above procedure.

[0650] The OTFT performance of Formulation 6(b) is shown below:

TABLE-US-00010 Channel length of Standard Number of working OTFT Mobility deviation of transistors tested on Formulation [microns] cm.sup.2/Vs mobility, % substrate (out of 36) Polymer Example (6) 50:50 8 1.81 28 35 9,9-bis(5-cyano-5- methylhexyl)fluorene:9,10- dioctylphenanthrene random copolymer and TMTES in bromobenzene/2- propanol mixed solvent

[0651] Organic thin film transistors (OTFT) fabricated using Formulation 6(b) as the semiconducting layer showed excellent charge carrier mobility at short channel length, and high device to device uniformity.