ORGANIC FIELD EFFECT TRANSISTOR COMPRISING SEMICONDUCTING SINGLE-WALLED CARBON NANOTUBES AND ORGANIC SEMICONDUCTING MATERIAL

Abstract

The present invention provides organic field effect transistors comprising a double layer consisting of i) a first layer comprising a percolating network of single-walled carbon nanotubes having a content of at least 95% by weight of semiconducting single-walled carbon nanotubes, and ii) a second layer comprising an organic semiconducting material, as well as a process for the preparation of the organic field effect transistor.

Claims

1. An organic field effect transistor comprising a double layer consisting of i) a first layer comprising a percolating network of single-walled carbon nanotubes having a content of at least 95% by weight of semiconducting single-walled carbon nanotubes, and ii) a second layer comprising an organic semiconducting material.

2. The organic field effect transistor of claim 1, wherein the percolating network of single-walled carbon nanotubes have a content of at least 99% by weight of semiconducting single-walled carbon nanotubes.

3. The organic field effect transistor of claim 1, wherein the first layer essentially consists of a percolating network of single-walled carbon nanotubes.

4. The organic field effect transistor of claim 1, wherein the single-walled carbon nanotubes have a diameter of 0.5 to 3 nm, and a length in the range of 0.1 to 100 m.

5. The organic field effect transistor of claim 1, wherein the organic semiconducting material is at least one diketopyrrolopyrrole-based material.

6. The organic field effect transistor of claim 5, wherein the diketopyrrolopyrrole-based material is i) a diketopyrrolopyrrole-based polymer comprising units of formula ##STR00024## wherein R.sup.1 is at each occurrence C.sub.1-30-alkyl, C.sub.2-30-alkenyl or C.sub.2-30-alkynyl, wherein C.sub.1-30-alkyl, C.sub.2-30-alkenyl and C.sub.2-30-alkynyl can be substituted by one or more Si(R.sup.a).sub.3 or OSi(R.sup.a).sub.3, or one or more CH.sub.2 groups of C.sub.1-30-alkyl, C.sub.2-30-alkenyl and C.sub.2-30-alkynyl can be replaced by Si(R.sup.a).sub.2 or [Si(R.sup.a).sub.2O].sub.aSi(R.sup.a).sub.2, wherein R.sup.a is at each occurrence C.sub.1-10-alkyl, and a is an integer from 1 to 20, n and m are independently 0 or 1, and Ar.sup.1 and Ar.sup.2 are independently arylene or heteroarylene, wherein arylene and heteroarylene can be substituted with one or more C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl or heteroaryl, which C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl, L.sup.1 and L.sup.2 are independently selected from the group consisting of ##STR00025## wherein Ar.sup.3 is at each occurrence arylene or heteroarylene, wherein arylene and heteroarylene can be substituted with one or more C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl or heteroaryl, which C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-3-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-2-alkyl, OC.sub.1-20-alkyl or phenyl; and wherein adjacent Ar.sup.3 can be connected via a CR.sup.bR.sup.b, SiR.sup.bR.sup.c or GeR.sup.bR.sup.b linker, wherein R.sup.b is at each occurrence H, C.sub.1-30-alkyl or aryl, which C.sub.1-30-alkyl and aryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl, b is at each occurrence an integer from 1 to 8, and Ar.sup.4 is at each occurrence aryl or heteroaryl, wherein aryl and heteroaryl can be substituted with one or more C.sub.1-30-alkyl, OC.sub.1-3-alkyl or phenyl, which phenyl can be substituted with C.sub.1-20-alkyl or OC.sub.1-20-alkyl, or ii) a diketopyrrolopyrrole-based small molecule of formulae ##STR00026## wherein R.sup.2 is at each occurrence C.sub.1-30-alkyl, C.sub.2-30-alkenyl or C.sub.2-30-alkynyl, wherein C.sub.1-30-alkyl, C.sub.2-30-alkenyl and C.sub.2-30-alkynyl can be substituted by Si(R.sup.c).sub.3 or OSi(R.sup.c).sub.3, or one or more CH.sub.2 groups of C.sub.1-30-alkyl, C.sub.2-30-alkenyl and C.sub.2-30-alkynyl can be replaced by Si(R.sup.c).sub.2 or [Si(R.sup.c).sub.2O].sub.aSi(R.sup.c).sub.2, wherein R.sup.c is at each occurrence C.sub.1-10-alkyl, and a is an integer from 1 to 20, R.sup.3 is H, CN, C.sub.1-20-alkyl, C.sub.2-20-alkenyl, C.sub.2-20-alkynyl, OC.sub.1-20-alkyl, aryl or heteroaryl, which C.sub.1-20-alkyl, C.sub.2-20-alkenyl, C.sub.2-20-alkynyl, OC.sub.1-20-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-6-alkyl, OC.sub.1-6-alkyl or phenyl, x and y are independently 0 or 1, and Ar.sup.5 and Ar.sup.6 are independently arylene or heteroarylene, wherein arylene and heteroarylene can be substituted with one or more C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl or heteroaryl, which C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl; L.sup.3 and L.sup.4 are independently selected from the group consisting of ##STR00027## wherein Ar.sup.7 is at each occurrence arylene or heteroarylene, wherein arylene and heteroarylene can be substituted with one or more C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl or heteroaryl, which C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl; and wherein adjacent Ar.sup.7 can be connected via an CR.sup.dR.sup.d, SiR.sup.dR.sup.d or GeR.sup.dR.sup.d linker, wherein R.sup.d is at each occurrence H, C.sub.1-30-alkyl or aryl, which C.sub.1-30-alkyl and aryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl, c is at each occurrence an integer from 1 to 8, and Ar.sup.8 is at each occurrence aryl or heteroaryl, wherein aryl and heteroaryl can be substituted with one or more C.sub.1-30-alkyl, OC.sub.1-30-alkyl or phenyl, which phenyl can be substituted with C.sub.1-20-alkyl or OC.sub.1-20-alkyl.

7. The organic field effect transistor of claim 6, wherein the diketopyrrolopyrrole-based material is a diketopyrrolopyrrole-based polymer comprising units of formula (1) as defined in claim 6.

8. The organic field effect transistor of claim 7, wherein the diketopyrrolopyrrole-based material is a diketopyrrolopyrrole-based polymer essentially consisting of units of formula (1) as defined in claim 6.

9. The organic field effect transistor of claim 8, wherein the diketopyrrolopyrrole-based materials is a diketopyrrolopyrrole-based polymer essentially consisting of units of formula ##STR00028## wherein R.sup.1 is C.sub.6-30-alkyl, n and m are independently 0 or 1, provided n and m are not both 0, and Ar.sup.1 and Ar.sup.2 are independently ##STR00029## L.sup.1 and L.sup.2 are independently selected from the group consisting of ##STR00030## wherein Ar.sup.3 is at each occurrence arylene or heteroarylene, wherein arylene and heteroarylene can be substituted with one or more C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl or heteroaryl, which C.sub.1-30-alkyl, C.sub.2-30-alkenyl, C.sub.2-30-alkynyl, OC.sub.1-30-alkyl, aryl and heteroaryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl; and wherein adjacent Ar.sup.3 can be connected via a CR.sup.bR.sup.b, SiR.sup.bR.sup.c or GeR.sup.bR.sup.b linker, wherein R.sup.b is at each occurrence H, C.sub.1-30-alkyl or aryl, which C.sub.1-30-alkyl and aryl can be substituted with one or more C.sub.1-20-alkyl, OC.sub.1-20-alkyl or phenyl, b is at each occurrence an integer from 1 to 8, and Ar.sup.4 is at each occurrence aryl or heteroaryl, wherein aryl and heteroaryl can be substituted with one or more C.sub.1-30-alkyl, OC.sub.1-30-alkyl or phenyl, which phenyl can be substituted with C.sub.1-20-alkyl or OC.sub.1-20-alkyl.

10. The organic field effect transistor of claim 9, wherein the diketopyrrolopyrrole-based materials is a diketopyrrolopyrrole-based polymer essentially consisting of units of formula ##STR00031## wherein R.sup.1 is ##STR00032## wherein R.sup.f is C.sub.6-14-alkyl, R.sup.g is C.sub.2-12-alkyl, n and m are independently 0 or 1, provided n and m are not both 0, and Ar.sup.1 and Ar.sup.2 are ##STR00033## L.sup.1 and L.sup.2 are independently selected from the group consisting of ##STR00034## wherein R.sup.h and R.sup.i are independently C.sub.6-30-alkyl, and d and e are independently 0 or 1.

11. The organic field effect transistor of claim 1, wherein the organic field effect transistor is a bottom-gate organic field effect transistor.

12. The organic field effect transistor of claim 11, wherein the second layer of the double layer is on top of the first layer of the double layer.

13. The organic field effect transistor of claim 12, wherein the first layer of the double layer is on top of an adhesion layer.

14. A process for the preparation of the organic field effect transistor of claim 1 comprising the steps of i) depositing a composition comprising single-walled carbon nanotubes having a content of at least 95% by weight of semiconducting single-walled carbon nanotubes in order to form a first layer comprising a percolating network of single-walled carbon nanotubes having a content of at least 95% by weight of semiconducting single-walled carbon nanotubes, and ii) depositing a composition comprising organic semiconducting material in order to form a second layer comprising an organic semiconducting material.

Description

[0135] FIG. 1 shows a process for the preparation of a bottom-gate, top-contact (BGTC) organic field effect transistor of the present invention comprising a double layer consisting of i) a first layer comprising a percolating network of single-walled carbon nanotubes (SWCNT) having a content of at least 95% by weight of semiconducting single-walled carbon nanotubes, and ii) a second layer comprising an organic semiconducting material (OSC).

[0136] FIG. 2 shows a field emission scanning electron microscope (FESEM) image of a first layer comprising a percolating network of single walled carbon nanotubes having a content of 99.9% by weight of semiconducting single-walled carbon nanotubes prepared by drop casting a commercially available single-walled carbon nanotube composition (IsoNanotubes-S having a content of semiconducting single-walled carbon nanotubes of 99.9%, from Nanointegris Inc., concentration of SWCNT in the solution was 0.001 wt %, diameter range: 1.2 to 1.7 nm, length range: 300 nm to 5 m) on a poly-L-lysine adhesion layer.

[0137] FIG. 3 shows the transfer characteristics drain current (Id) against gate-source voltage (Vg) of the bottom-gate, top-contact (BGTC) organic field effect transistor of example 2 comprising polymer 1a as organic semiconducting material in the saturation regime, while the gate voltage was scanned from 10 to 30 V.

EXAMPLES

Example 1

[0138] Preparation of Semiconducting Polymer of Formula 1a

##STR00023##

[0139] 733 mg (2.181 mmol) of compound 4, 1972 mg (2.181 mmol) of compound 5, 78.30 mg of tris(dibenzylideneacetone)dipalladium(0) (Pd.sub.2(dba).sub.3) and 48.15 mg of tri-tert-butyl-phosphonium tetrafluoroborate ((tert-Bu).sub.3PHBF.sub.4) are placed together in 50 ml of tetrahydrofuran under Argon. The reaction mixture is heated to reflux, and then 1600 mg potassium phosphate in 5 ml of degassed water is added. The reaction mixture is refluxed overnight. Then, the reaction mixture is poured on water and the precipitate is filtered and washed with water and methanol. The precipitate is then Soxhlet fractionated with heptane, tetrahydrofuran, toluene, chloroform and chlorobenzene. To remove catalyst residues, the selected fraction is evaporated and the residue is dissolved in 150 ml of chlorobenzene. Then 50 ml of a 1% NaCN aqueous solution is added and the mixture is heated and stirred overnight at reflux. The phases are separated and the organic phase is washed 3 times with 10 ml of deionized water for 3 hours at reflux. Polymer 1a is then precipitated from the organic phase by addition of methanol. The precipitated polymer 1a is filtered, washed with methanol and dried. UV-VIS-absorption spectrum: .sub.max: 840 nm (film) and 840 nm (10.sup.5 M solution in toluene).

Example 2

[0140] Preparation of a Bottom-Gate, Top-Contact (BGTC) Organic Field Effect Transistor Comprising a Double Layer Consisting of a First Layer Essentially Consisting of a Percolating Network of Single-Walled Carbon Nanotubes Having a Content of Semiconducting Single-Walled Carbon Nanotubes of 99.9%, and a Second Layer Essentially Consisting of the Diketopyrrolopyrrole-Based Polymer 1a of Example 1

[0141] A bottom-gate, top-contact (BGTC) thin film transistor (TFT) with channel length (50 m) and width (500 om) was prepared. Heavily doped Si substrate (200 nm of SiO.sub.2 thickness) was cleaned by acetone, isopropanol and deionized water using sonication for 1 min each time. Then, O.sub.2 plasma was applied (100 sccm, 50 W for 60 sec) to make the surface hydrophilic. To enhance the adhesiveness of the surface to single-walled carbon nanotubes, poly-L-lysine solution (0.1% w/v in water, Sigma Aldrich) was deposited by immersion technique for 5 min. Then, the surface was thoroughly rinsed with deionized water and dried at 95 C. on a hot plate for 1 min. Commercially available purified aqueous single-walled carbon nanotubes (SWCNT) solution (IsoNanotubes-S having a content of semiconducting single-walled carbon nanotubes of 99.9%, from Nanointegris Inc., concentration of SWCNT in the solution was 0.001 wt %, diameter range: 1.2 to 1.7 nm, length range: 300 nm to 5 m) was deposited by drop casting onto the surface and baked at 95 C. on a hot plate for 3 min. The drop casting depositing of the SWCNT solution was repeated twice. After having placed the substrate with deposited SWCNTs in the air for 10 min, the substrate was dried 3 min at 95 C. on hot plate, followed by rinsing with water, carefully drying with N.sub.2 gas and annealing at 150 C. on a hot plate for 1 h. A solution of 0.75 wt % semiconducting polymer of formula 1a of example 1 in toluene was blade-coated onto the SWCNT layer at 120 C. The gap and speed of the blade coater was 100 m and 30 mm/sec, respectively. Finally, source and drain electrode of Au were deposited (50 nm of thickness) by thermal evaporation.

[0142] A field emission scanning electron microscope (FESEM) image of the first layer essentially consisting of a percolating network of single-walled carbon nanotubes having a content of 99.9% by weight of semiconducting single-walled carbon nanotubes on the poly-L-lysine adhesion layer is shown in FIG. 2.

Example 3

[0143] Electrical Characterization of the Bottom-Gate, Top-Contact (BGTC) Organic Field Effect Transistor of Example 2

[0144] The electrical characterization of the BGTC organic field effect transistor of example 2 was conducted under ambient condition at room temperature using Keithley 4200-SCS.

[0145] FIG. 3 shows the transfer characteristics drain current (Id) against gate-source voltage (Vg) of the BGBC TFT of example 2 in the saturation regime, while the gate voltage was scanned from 10 to 30 V.

[0146] The saturation field effect mobility of the bilayer structure in active layer is 58 cm.sup.2Vs. The Ion/off is 10.sup.3.