Investigation of the source-drain electrodes/the active layer contact-effect on the performance of organic phototransistor

•Pentacene-OPT with Au electrodes obtains higher photoresponsivity than that with Al.•CuPc-OPT with Al Shottky contact achieves a higher PMAX than that with Au electrodes.•The improved PMAX effects in Al-CuPc-OPT can be ascribed to PIBL effect.•The physical mechanism of photon induced barrier lowering in OPT was studied.•Schottky barrier of source-drain/active layer plays a beneficial role in some OPTs.