Bias‐Induced Gradient Bandgap of Bulk Perovskite Boosting Built‐In Electric Fields for High‐Performance Self‐Powered Photodetectors

Abstract Self‐powered photodetectors (PDs) have gained significant attention in recent years due to their ability to operate without external power. Strengthening the built‐in electric field ( E bi ) of these devices is crucial for efficient carrier separation and transport. However, the disordered energy level arrangement within mixed halide perovskites (MHP) often conflicts with the energy levels constructed by the external interface, weakening the E bi and thus affecting the performance of self‐powered PDs. In this study, a bias‐induced gradient bandgap of bulk MHP is proposed for high‐performance self‐powered photodetectors. The vector superposition of the bias‐induced gradient bandgap with the interface electric field significantly boosts the E bi of the device, providing a powerful driving force for the separation and transport of photogenerated carriers. The obtained device exhibits exceptional performance, including an ultra‐fast response time of 1.14/1.75 µs, a large specific detectivity of 7.27 × 10 12 cm Hz 1/2 W −1 , an ultra‐high responsivity of 0.49 A W −1 , and an external quantum efficiency of 93.5% at 0 V bias. Furthermore, this strategy is also demonstrated in lateral structure photodetector. This work offers valuable guidance for achieving high‐performance MHP‐based self‐powered PDs through bias‐induced gradient bandgap optimization.