Achieving photomultiplication in organic-MOF complex via interface and band engineering

Abstract

This work studies a hybrid broadband photodetector with and without metal–organic framework nanosheets with an inverted structure. It is observed that an inverted structure provides photomultiplication in the devices with both positive and negative biases. This phenomenon is believed to be due to a non-uniform TiO2/active layer interface where the porosity of TiO2 facilitates structural traps, in turn achieving photomultiplication in P3HT: PCBM (1:1) devices. Meanwhile, in photodetectors with an active layer of P3HT:ZnTCPP:PCBM (1:0.5:1), photomultiplication is attributed to interface traps and band alignment due to ZnTCPP nanosheets. The presence of ZnTCPP reduces the dip in EQE at 370–460 and 530–610 nm range, thus improving broadband detection (300–700 nm). Adding ZnTCPP to the devices results in improved rise and fall times. The on–off response is also relatively stable for the devices with ZnTCPP and has high detectivity (1011 Jones). Thus, this study sheds light on the role of a thin interface layer of TiO2 in photomultiplication and improving performance parameters with ZnTCPP nanosheets.