Self-powered Schottky barrier photodetectors based on P3HT:PC61BM bulk heterojunction films

Abstract

By employing the classic system poly(3-hexylthiophene-2,5-diyl): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM), organic bulk heterojunction films were applied on an indium tin oxide substrate using a one-step spin-coating method, without requiring any complex manufacturing processes, to obtain self-powered photodetectors (PDs) with a simple preparation process. The fullerene material was introduced to create a bulk heterojunction film with proper phase separation and greatly enrich the donor/acceptor dissociation interface, thus improving the high exciton binding energy and short exciton diffusion distance. The built-in electric field formed by the Schottky junction at the interface between the active layer and electrode can enhance the separation of excitons and the transport of charge carriers, realizing optical detection without external energy sources. Moreover, femtosecond transient absorption was employed to investigate the exciton dynamics in organic films and analyze the working mechanism of self-powered detection performance. The long-lived behavior of carriers and the formation of charge transfer states were further verified, which contributed to the enhanced performance of the device. As a result, the self-powered PD-based Schottky bulk heterojunction presents a high light on/off ratio of over 104 (0 V) and fast response speed with rise and decay times of 33 and 36 µs, respectively, under a 532 nm light illumination. These results provide theoretical and experimental verification of this technique for the development of self-powered PDs in the field of organic materials.