Photocurrent studies of sexythiophene-based OFETs.

Photocurrent (PC) spectroscopy is proposed as a reliable tool in the investigation of the transport properties of organic thin-film transistors (OFETs). We have applied PC analyses to the study of the electronic density of states (DOS) distribution of the OFETs with crystalline-mixed films of two derivatives of a conjugated molecule [ α-sexithiophene (6T), and its alkylated analogue α, ω-dihexylsexithiophene (DH6T)] as the active semiconductor. We have investigated the modifications in the DOS distribution associated to variations in the carrier density in the OFET channel and we have detected the formation of deep electrically active states in the below-band-gap region, associated to polaron states induced by a prolonged exposure of the device to atmosphere. A clear correlation between the PC results and the electrical characteristics of the corresponding FET devices has been observed. [ABSTRACT FROM AUTHOR]