High performance organic phototransistor based on regioregular poly(3-hexylthiophene)

We fabricated solution processed organic phototransistors (OPT) by drop casting regioregular poly 3-hexylthiophene (P3HT) from three different solvents: p-xylene, dichlorobenzene and chloroform. The best performance was obtained for films drop-casted from p-xylene with a maximum photosensitivity (P) of 3.8 x 10(3) and responsivity (R) of 250 A W(-1) under white light illumination. For films deposited from dichlorobenzene and chloroform the values of P were 1.1 x 10(3) and 30, respectively, while the values of R were 150 and 35, respectively. The maximum responsivity value reported here is at least one order of magnitude higher than that of previously reported solution processed OPT devices. By analyzing the absorption spectra of different films, we conclude that the better device performance of OPT from p-xylene is due to better crystallinity of P3HT. Demonstration of high performance OPTs is a significant step forward in integrating these devices in various optoelectronic circuits.