Solution process for fabricating high-performance organic thin-film transistors

Abstract

The present invention relates to a solution or ink composition for fabricating high-performance thin-film transistors. The solution or ink comprises an organic semiconductor and a mediating polymer such as polyacrylonitrile, polystyrene, or the like or mixture thereof, in an organic solvent such as chlorobenzene or dichlorobenzene. The percentage ratio by weight of semiconductor:mediating polymer ranges from 5:95 to 95:5, and preferably from 20:80 to 80:20. The solution or ink is used to fabricate via solution coating or printing a semiconductor film, followed by drying and thermal annealing if necessary to provide a channel semiconductor for organic thin-film transistors (OTFTs). The resulting OTFT device with said channel semiconductor has afforded OTFT performance, particularly field-effect mobility and current on/off ratio that are superior to those OTFTs with channel semiconductors fabricated without a mediating polymer.

1 . A solution-based method of fabricating a channel semiconductor for organic thin-film transistors comprising:
 dissolving an organic semiconductor in a solvent with a matrix polymer at a percentage ratio by weight of semiconductor:matrix polymer ranging from 5:95 to 95:5, to produce a solution;   spin casting or printing said solution on a substrate to produce a channel semiconductor, wherein the resultant thin-film transistor has a field effect mobility of greater than or equal to 2 cm 2 V −1 s −1  and a current on/off ratio of greater than or equal to 10 5 .   
     
     
         2 . The method according to  claim 1  wherein the percentage ratio by weight of semiconductor:matrix polymer ranges from 20:80 to 80:20. 
     
     
         3 . The method according to  claim 1  wherein the resultant thin-film transistor has a field effect mobility of greater than or equal to 5 cm 2 V −1 s −1  and a current on/off ratio of greater than or equal to 10 5 . 
     
     
         4 . The method according to  claim 1  wherein the resultant thin-film transistor has a field effect mobility of greater than or equal to 8 cm 2 V −1 s −1  and a current on/off ratio of greater than or equal to 10 5 . 
     
     
         5 . The method according to  claim 1  wherein the percentage ratio by weight of semiconductor:matrix polymer ranging from 30:70 to 70:30. 
     
     
         6 . The method according to  claim 1  wherein the matrix polymer comprises polyacrylonitrile, polystyrene, poly(methyl methacrylate), poly(methyl methacrylate-alt-styrene), polyvinyl chloride, or mixtures thereof. 
     
     
         7 . The method according to  claim 1  wherein the semiconductor comprises a polymer semiconductor including a diketopyrrolopyrrole-based polymer or regioregular poly(3-hexylthiophene), or a mixture thereof. 
     
     
         8 . The method according to  claim 1  wherein the semiconductor comprises a polymer selected from: 
       
         
           
           
               
               
           
         
       
     
     
         9 . The method according to  claim 1  wherein the semiconductor comprises one or more organic small molecular compounds. 
     
     
         10 . The method according to  claim 1  further comprising drying with thermal annealing after spin casting or printing of solution on a substrate. 
     
     
         11 . The method according to  claim 1  wherein the substrate comprises a metalized plastic substrate coated with a thin layer of metal oxide. 
     
     
         12 . The method according to  claim 1  wherein the metal oxide is aluminum oxide or hafnium oxide.