Thermal annealing induced enhancement in the performance of polymer field-effect transistor using poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester

Abstract

Polymer field-effect transistors with a field-effect mobility of μ≈0.3 cm 2V·s have been demonstrated using regioregular poly(3-hexylthiophene) (rr-P3HT). Devices were fabricated by dip-coating the semiconducting polymer followed by annealing at 150°C for 10 minutes. The heat annealed devices exhibit an increased field-effect mobility compared with the as-prepared devices. Morphology studies and analysis of the channel resistance demonstrate that the annealing process increases the crystallinity of rr-P3HT and improves the contact between the electrodes and the P3HT films, thereby increasing the field effect mobility of the films. Based on the results obtained from unipolar FETs using rr-P3HT, we have also applied postproduction heat treatment to ambipolar polymer FETs fabricated with rr-P3HT and C 61-butyric acid methyl ester (PCBM). Devices were fabricated using aluminum (Al) source and drain electrodes to achieve an equivalent injection for the both holes and electrons. As the case of P3HT unipolar FETs, the thermal annealing method also improves the film morphology, crystallinity, and the contact properties between Al and active layer, thereby resulting in excellent ambipolar characteristics with the hole mobility of 1.7×10 -3 cm 2/V·s and the electron mobility of 2.0×10 -3 cm 2V·s.