Air-stability and bending properties of flexible organic field-effect transistors based on poly[N-9′-heptadecanyl-2, 7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′, 3′-benzothiadiazole)]

We have fabricated flexible field-effect transistors (FETs) using poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)], PCDTBT, as an active channel, poly(methyl methacrylate) (PMMA) as gate dielectric and biaxially oriented poly-ethyleneterephthalate (BOPET) as supporting substrate. The output and transfer characteristics of the devices were measured as a function of channel length. It has been observed that various OFET parameters viz. on-off ratio (similar to 10(5)), mobility (mu similar to 10 (4) cm(2) V (1) s (1)), threshold voltage (Vth similar to -14 V), switch-on voltage (V-so similar to -6 V), subthreshold slope (S similar to 7 V/decade) and trap density (N-it similar to 10(14) cm (2) V (1)) are almost independent of the channel length, which suggested a very high uniformity of the PCDTBT active layer. These devices were highly stable under atmospheric conditions (temperature: 20-35 degrees C and relative humidity: 70-85%), as no change in mobility was observed on a continuous exposure for 70 days. The studies on the effect of strain on mobility revealed that devices are stable up to a compressive or tensile strain of 1.2%. These results indicate that PCDTBT is a very promising active layer for the air stable and flexible FETs. (C) 2013 Elsevier B. V. All rights reserved.