Flexible organic ion-gated transistors with low operating voltage and light-sensing application

Abstract

Ion-gated transistors are attracting significant attention due to their low operating voltage (<1 V) and modulation of charge carrier density by ion-gating media. Here we report flexible organic ion-gated transistors based on the high mobility donor–acceptor conjugated copolymer poly[4-(4,4-dihexadecyl 4H-cyclopenta[1,2-b:5,4-b′]-dithiophen-2-yl)-alt[1,2,5]thiadiazolo[3,4c]pyridine](PCDTPT) and the ionic liquid [1-ethyl-3 methylimidazolium bis(trifluoromethylsulfonyl)imide] as the ion-gating medium. Electrical characteristics of devices made on both [rigid (SiO _2 /Si) and flexible (polyimide (PI))] substrates showed very similar values of hole mobility (∼1 cm ^2 V ^−1 s ^−1 ) and ON–OFF ratio (∼10 ^5 ). Flexible ion-gated transistors showed good mechanical stability at different bending curvature radii and under repetitive bending cycles. The mobility of flexible ion-gated transistors remained almost unchanged upon bending. After 1000 bending cycles the mobility decreased by 20% of its initial value. Flexible photodetectors based on PCDTPT ion-gated transistors showed photosensitivity and photoresponsivity values of 0.4 and 93 AW ^−1 .

Keywords

• ion-gated transistor
• donor–acceptor conjugated copolymer
• poly[4-(4, 4-dihexadecyl 4H-cyclopenta[1, 2-b:5, 4-b′]-dithiophen-2-yl)-alt[1, 2, 5]thiadiazolo[3, 4c]pyridine](PCDTPT)
• flexible electronics
• Ionic liquids