Synthesis of a conjugated polymer with broad absorption and its application in high-performance phototransistors

Abstract

An amorphous copolymer (PBDT-BBT) of 4,8-bis(2-thienyl)benzo[1,2-b:4,5- b′]dithiophene and 5,5′-bibenzo[c][1,2,5]thiadiazole was synthesized by Stille coupling polymerization. PBDT-BBT exhibited good solution processability, excellent thermal stability with decomposition temperature of 437 °C, broad absorption (300-800 nm), deep HOMO level (-5.7 eV), and LUMO level (-3.7 eV). The microstructure order of PBDT-BBT thin films is not susceptible to thermal annealing temperature (80-200 °C). Field-effect transistors based on this polymer exhibited a charge-carrier mobility of 6 × 10 -3 cm 2 V -1 s -1, threshold voltage of -1 V, and on/off current ratio of 10 6 without any post-treatments. Thin film phototransistors of PBDT-BBT exhibited a photoresponsivity of 3200 mA W -1 and photocurrent/dark current ratio of 4 × 10 5. © 2012 American Chemical Society.