Polymer transistor

1. A transistor, comprising:

a semiconductive layer; and

a gate dielectric layer comprising an insulating polymer,

wherein, the insulating polymer forms an interface with the semiconductive layer;

the insulating polymer is crosslinked and comprises one or more units having a low cohesive-energy-density and one or more crosslinking groups and the insulating polymer includes substantially no residual —OH leaving groups, and

wherein the semiconductive layer comprises an organic semiconductor.

2. A transistor according to claim 1 , wherein the transistor is a field-effect transistor.

3. A transistor according to claim 1 , wherein the transistor is a phototransistor.

4. A transistor according to claim 1 , wherein the transistor is a chemical sensor.

5. A transistor according to claim 1 , wherein the charge-carrier mobility at the semiconductive layer/gate dielectric layer interface is in the range from 10 −5 to 10 cm 2 /V s.

6. A transistor according to claim 1 , wherein the gate dielectric is thermally stable up to 150° C.

7. A transistor according to claim 1 , wherein the insulating polymer has a dielectric breakdown strength of more than 0.5 MV/cm.

8. A transistor according to claim 1 , wherein the insulating polymer has a static dielectric constant of at least 2.2.

9. A transistor according to claim 1 , wherein the backbone of the insulating polymer comprises one or more low cohesive-energy-density structural units.

10. A transistor according to claim 1 , wherein the low cohesive-energy-density structural unit comprises an Si(R) 2 —O—Si(R) 2 , Si(R) 2 —O—Si(R), or Si(R)—O—Si(R) unit where each R independently comprises a hydrocarbon.

11. A transistor according to claim 1 , wherein the backbone of the insulating polymer comprises a repeat unit comprising Si(R) 2 —O—Si(R) 2 , Si(R) 2 —O—Si(R), or Si(R)—O—Si(R) where each R independently is methyl or substituted or unsubstituted phenyl.

12. A transistor according to claim 1 , wherein the crosslinking group is derivable from a crosslinkable group that can be cured without the loss of a leaving group.

13. A transistor according to claim 12 , wherein the insulating polymer comprises a repeat unit having general formula IV:

where each X is the same or different and each X represents a crosslinking group and each R independently is a group selected from the group consisting of siloxane, alkyl, aryl, cycloalkyl, alkoxy, and aryloxy groups.

14. A transistor according to claim 13 , wherein each crosslinking group comprises 2,3-disubstituted tetrahydronaphthalene.

15. A transistor according to claim 14 , wherein the insulating polymer comprises:

where each R independently is an alkyl group or an aromatic group.

16. A transistor according to claim 12 , wherein the insulating polymer comprises a repeat unit having general formula V or VI:

where each X is the same or different and each X represents a crosslinking group and each R independently is a group selected from the group consisting of siloxane, alkyl, aryl, cycloalkyl, alkoxy, and aryloxy groups.

17. A transistor according to claim 16 , wherein each X independently comprises a group having general formula XIV:

where R 11 to 14 =—H, —CH 3 ; and R 21 to 23=—H, —CH 3 .

18. A transistor according to claim 16 , wherein each X independently comprises a group having general formula XIX:

where R 51 to 53 =—H, —CH 3 ; and R 21 to 23 =—H, —CH 3 .

19. A transistor according to claim 16 , wherein each X independently comprises a group having general formula XXIV or XXV:

where R 31 to 33 =—H, —CH 3 , or -Ph; and R 41 =alkyl, or aryl.

20. A transistor according to claim 16 , wherein each X independently comprises a group having general formula XXVIII:

where R 61 to 63 =—H, —CH 3 , or -Ph.

21. A transistor according to claim 1 , wherein the thickness of the gate dielectric layer is below 400 nm.

22. A transistor according to claim 21 , wherein the operational voltage of the transistor is less than 30 volts.

23. A transistor according to claim 1 , wherein the semiconductive layer comprises a semiconductive polymer comprising a fluorene and/or a triarylamine repeat unit.

24. A transistor according to claim 1 , wherein the thickness of the semiconductive layer is in the range of 10 nm to 300 nm.

25. An electronic paper, a logic circuit or an RF tag including a transistor according to claim 1 .

26. Use in a transistor, comprising a semiconductor layer and a gate dielectric layer forming an interface with the semiconductor layer, of (1) a crosslinked polymer comprising one or more units having a low cohesive-energy-density and one or more crosslinking groups and substantially not including any residual —OH leaving groups, as a gate dielectric for the gate dielectric layer forming an interface with the semiconductor layer, and (2) an organic semiconductor as the semiconductor layer.

27. The transistor as recited in claim 1 wherein the semiconductor layer comprises a polymer.

28. The use in a transistor of a crosslinked polymer as recited in claim 26 , wherein the semiconductor layer comprises a polymer.