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

Abstract

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_xO: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_xO: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_xO: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 (>10¹² 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.