Bias-Switchable Dual-Mode Organic Photodiodes Enabled by Manipulation of Interface Layers

Bias-switchable dual-mode organic photodiodes (OPDs) that integrate photovoltaic and photomultiplication modes are recently developed and shown prospects in complex light-intensity applications. Yet, the device physics that focuses on carrier dynamics is still a challenge and needs to be further explored. Herein, dual-mode OPDs are developed through interface layer manipulation, that is, introducing cathode interface layers (typically, Zn x O:D149) with deep energy levels and abundant bulk defects and an anode interface layer of thermally-evaporated ZnO (e-ZnO) with a wide bandgap. Under reverse bias, Zn x O:D149 forms a barrier wall to effectively block external holes and maintain the photovoltaic mode of the OPDs. Under forward bias, the capturing effect of Zn x O:D149 and blocking effect of e-ZnO help to reduce the dark current; when under illumination, defect traps capture photo-generated holes, eliminating the barrier traps and promoting unobstructed injection of external carriers to achieve photomultiplication effect. The typical device delivers high specific detectivity (>10 12 Jones) and fast response (<40 µs), and exhibits disparate external quantum efficiency in two operating modes, showing promise for simultaneously detecting faint and strong light. This general strategy for preparing dual-mode OPDs is compatible with CMOS processing technology and meets the miniaturization and integration requirements of next-generation detection systems.