Tunable photocurrent switching behavior of a ZnO/Cu2O heterojunction photodetector to realize bipolar binary photoresponse

The tunable bipolar binary photoresponse characteristics (positive and negative current value changes) of heterojunction photodetectors (PDs) are used to realize the applications of optical communications, optical information storage, and multiple logic circuit operations of light. ZnO/Cu2O heterojunction PDs with photovoltaic effects show a fast and broad-spectrum photoresponse to UV and visible light. A high light switching on/off ratio of 2.7 × 105, a responsivity of 0.55 A W−1 and a detectivity of 1.5 × 1013 Jones were obtained under 470 nm illumination without applied bias. The PDs exhibit controllable bipolar binary photoresponse characteristics by adjusting the competitive relationship between the photo-generated current and the internal junction current for the PDs under different light (intensity or wavelength) and small applied bias voltage (0 < Vbias < Voc). The PDs exhibit a binary photoresponse in a wide spectrum from UV to visible light. The binary photoresponse states used as “1” and “−1” digital codes can achieve programmable processing of digital signals. The results provide a universal example to realize the bipolar binary photoresponse by regulating the light wavelength, light intensity and applied external bias for the heterojunction PDs with the photovoltaic effect.