ORGANIC SEMICONDUCTOR COMPOSITION AND SEMICONDUCTING LAYER OBTAINED THEREFROM

Abstract

The present invention concerns a composition comprising at least one crystalline organic semiconductor and at least one triarylamine of formula provided at least one of Ar.sub.1, Ar.sub.2 and Ar.sub.3 comprises at least two fused aromatic rings.

##STR00001##

Claims

1. A composition comprising at least one crystalline organic semiconductor and at least one triarylamine of formula 1 ##STR00040## wherein each of Ar.sub.1, Ar.sub.2 and Ar.sub.3 independently represents an optionally substituted aryl or an optionally substituted heteroaryl group, provided at least one of Ar.sub.1, Ar.sub.2 and Ar.sub.3 comprises at least two fused aromatic or heteroaromatic rings.

2. The composition according to claim 1 wherein the triarylamine has a molecular weight of 1600 Daltons or less.

3. The composition according to claim 1 wherein the crystalline semiconductor has a field effect mobility of at least 0.01 cm.sup.2/Vs.

4. The composition according to claim 1 wherein the weight ratio of crystalline organic semiconductor to triarylamine is comprised from 5/95 to 95/5.

5. The composition according to claim 1 wherein the composition is essentially free of solvent.

6. The composition according to claim 1, further comprising at least one organic solvent.

7. A method, comprising manufacturing a semiconducting layer using the composition according to claim 1.

8. A process for the manufacture of an organic semiconducting layer comprising applying the composition according to claim 1 onto a substrate to form a layer.

9. The process according to claim 8, wherein the composition further comprises at least one organic solvent and the process further comprises evaporating the solvent from the layer.

10. A device comprising the composition according to claim 1.

11. The device according to claim 10, wherein the device is or comprises a field effect transistor.

12. The device according to claim 11, wherein the device is a field effect transistor.

13. A display comprising the device according to claim 12.

14. A device comprising the organic semiconducting layer manufactured by the process according to claim 8.

15. The device according to claim 14, wherein the device is or comprises a field effect transistor.

16. The device according to claim 15, wherein the device is a field effect transistor.

17. A display comprising the device according to claim 16.

Description

EXAMPLES

[0117] Organic Thin Film Transistors (OTFTs) were fabricated in top gate and bottom contact configuration using glass based substrates as detailed hereinafter.

[0118] 1 square glass substrates (ex: Corning XG) were cleaned using sonication bathes for 5 minutes in Deconex (3% in water) followed by rinsing in ultrapure water and dried using compressed air. A planarization layer was first spin coated on top of the cleaned substrates in order to create a 30 nm film after photo-crosslinking Au (30 nm) bottom contact source/drain (S/D) electrodes were deposited on top of the planarization layer by thermal evaporation through a shadow mask. The 16 transistors S/D consisted of electrodes with channel length of 50 m and channel width of 0.5 mm. The substrates then underwent UV/O.sub.3 treatment (model 42-220, from Jelight Company, Inc.), treatment time 5 min. Prior to spin coating of the OSC solution, a 10 mM solution of 4-fluorobenzenethiol in 2-propanol was applied to the surface of the electrodes for 1 minute followed by spin coating and rinsing by fresh 2-propanol, followed by drying on a hotplate at 100 C. The organic semiconductor (OSC) formulation was spin coated onto the SD electrodes using a Laurell spinner set at 1500 rpm followed by baking on a hotplate for 60 seconds at 100 C. Hyflon AD SF 9.2% w/w solution commercialized by Solvay Specialty Polymers was spin coated at 3000 rpm and the samples were baked on a hotplate for 60 s at 100 C. Gate electrodes were defined by evaporation of Aluminum (60 nm) through a shadow mask in a thermal evaporator system.

[0119] OTFT Characterization

[0120] OTFTs were tested using a Cascade Microtech EP6 DC probe station in conjunction with an Agilent B1500A semiconductor parameter analyzer. The Agilent system calculated the linear mobility according to the equation shown below (Equation 2)

[00001]$\begin{array}{cc}{}_{\mathrm{Lin}}=\frac{I_{\mathrm{DS}}}{V_G}.Math.\frac{L}{{\mathrm{WC}}_i.Math.V_{\mathrm{DS}}}& \left(\mathrm{Equation}.Math..Math.2\right)\end{array}$

where L is the transistor length, W is the transistor width and C.sub.i is the dielectric capacitance per unit area. V.sub.DS was set at 4V unless otherwise stated. The mobility values reported are an average of the 5 highest points in accumulation for each transistor. The standard deviation of the mobility values is reported as a percentage of the mean.

Comparative Example 1: 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene without Triarylamine Binder; TG OTFT

[0121] The OTFT array fabricated and characterized as the comparative example 1 was fabricated and tested as described above. The formulation tested in the comparative example 1 included small molecule semiconductor however this formulation did not incorporate any triarylamine binder.

[0122] 1,4,8,11-tetramethyl-6,13-triethylsilylethynylpentacene represented by formula (OS1) was formulated in tetralin at 1.5% by weight total solids content. This was coated as an OSC layer in an OTFT device according to the method shown above for glass substrate.

[0123] The TFT performance of this formulation is shown below:

[0124] Lin=1.80.8 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 44.4%.

[0125] The OTFT array fabricated and characterized as the comparative example 2 was fabricated and tested as described above. The formulation tested in the comparative example 2 included a small molecule semiconductor and a triarylamine polymer as binder.

Comparative Example 2: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Triarylamine Polymer Binder; TG OTFT

[0126] 1,4,8,11-tetramethyl-6,13-triethylsilylethynylpentacene represented by formula (OS1) and Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] were formulated in tetralin in a ratio 50:50 at total solids content of 2% by weight. This was coated as an OSC layer in an OTFT device according to the method shown above for glass substrate.

[0127] The TFT performance of this formulation is shown below:

[0128] Lin=3.81.1 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 28.9%.

Examples 1 to 6

[0129] The OTFT arrays fabricated and characterized as the examples 1 to 6 were fabricated and tested as described above. The formulations tested in the examples 1 to 6 included small molecule semiconductor and an amorphous small-molecule triarylamine as binder. In these examples the ratio of binder to the semiconductor is in parts by weight.

Example 1: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0130] N4,N4-bis(4-cyclohexylphenyl)-N4,N4-di(naphthalen-1-yl)biphenyl-4,4-diamine (Binder 2), was formulated with 1,4,8,11-tetramethyl-6,13-triethylsilylethynyl pentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1.5% by weight in tetralin and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0131] The TFT performance of this formulation is shown below:

[0132] Lin=4.90.4 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 8.1%.

Example 2: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0133] N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9,9-bis(4-vinylbenzyl)-9H-fluorene-2,7-diamine (Binder 4), was formulated with 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1.5% by weight in tetralin and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0134] The TFT performance of this formulation is shown below:

[0135] Lin=5.10.5 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 9.8%.

Example 3: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0136] 2,2-(4,4-(biphenyl-4,4-diylbis(naphthalen-1-ylazanediyl))bis(4,1-phenylene))bis(2-methylpropanenitrile) (Binder 3), was formulated with 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1% by weight in tetralin and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0137] The TFT performance of this formulation is shown below:

[0138] Lin=5.00.4 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 8.0%.

Example 4: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0139] 2,2-(4,4-(biphenyl-4,4-diylbis(naphthalen-1-ylazanediyl))bis(4,1-phenylene))bis(2-methylpropanenitrile) (Binder 3), was formulated with 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1% by weight in anisole and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0140] The TFT performance of this formulation is shown below:

[0141] Lin=4.71.5 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 31.9%.

Example 5: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0142] N4,N4-bis(4-cyclohexylphenyl)-N4,N4-di(naphthalen-1-yl)biphenyl-4,4-diamine (Binder 2), was formulated with 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1% by weight in anisole and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0143] The TFT performance of this formulation is shown below:

[0144] Lin=9.71.7 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 17.5%.

Example 6: 1,4,8,11-Tetramethyl-6,13-Triethylsilylethynylpentacene with Small-Molecule Triarylamine Binder; TG OTFT

[0145] N4,N4-bis(4-tert-butylphenyl)-N4,N4-di(naphthalen-1-yl)biphenyl-4,4-diamine (Binder 1), was formulated with 1,4,8,11-tetramethyl-6,13-Triethylsilylethynylpentacene represented by formula (OS1) in a ratio 60:40 at a total solids content of 1% by weight in anisole and coated as an OSC layer in an OTFT device according to the method shown above for glass substrate devices.

[0146] The TFT performance of this formulation is shown below:

[0147] Lin=9.31.2 cm.sup.2/Vs; standard deviation as a % of the mean value of the mobility was 12.9%.

[0148] The previous examples show that the composition in accordance with the present invention, comprising an organic semiconductor and a small molecule triarylamine binder yielded OTFTs with improved performance compared to OTFTs obtained using compositions in accordance with the prior art. More particularly, measured linear mobility values were high, the standard deviation of the mobility values was low and the bias stress stability was improved.