Effects of molecular oxygen and ozone on polythiophene-based thin-film transistors
The effects of exposure of unencapsulated polymeric thin-film transistors (TFTs) to the ambient atmosphere, oxygen, and ozone were investigated. The off-state current increased and the threshold voltage became more positive for TFTs made with poly(3-hexylthiophene) P3HT, poly[5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene], PQT-12 and poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophenes) PBTTT when exposed to the ambient atmosphere. Exposure to purified air did not change the electrical characteristics of TFTs made with these materials over periods of months. Brief exposure to ozone caused similar changes to exposure to the ambient. Density functional calculations showed that ozone forms a complex with polythiophene that is a shallow acceptor and could cause doping. These results suggest that the small amount of ozone in the ambient causes the changes in electrical characteristics of polythiophene-based TFTs rather than oxygen.
Chabinyc, M. ; Street, R. A. ; Northrup, J. E. Effects of molecular oxygen and ozone on polythiophene-based thin-film transistors. Applied Physics Letters. 2007 March 19; 90 (12): 123508.