Gradient Doping Triggers Flexo-Pyroelectric Effects toward Self-Powered Broadband Photodetection and Smart...

Broadband self-powered photodetectors (PDs) are pivotal for intelligent sensing in complex environments, yet simultaneously achieving deep-ultraviolet to near-infrared (DUV-NIR) detection and high responsivity remains a formidable challenge. Here, we propose a device-level strategy to engineer a controllable flexoelectric polarization field by designing a precise compressive strain gradient. This design synergizes with the material's inherent pyroelectric effect, termed the flexo-pyroelectric effect, to substantially enhance the built-in electric field and overall photoresponse of a graded p-Si/n-ZnO:Ga heterojunction. The resulting device operates as a self-powered photodetector with an ultrabroadband spectral response from 200 to 1550 nm, delivering a peak transient responsivity of 2.24 A W^-1 and an external quantum efficiency exceeding 100%. Notably, leveraging its nonlinear optical response, the detector demonstrates substantial potential for smart sensing, as evidenced by its capability for the quantitative identification of environmental pollutants. This work not only presents a novel pathway for harnessing flexoelectricity in functional optoelectronics but also provides a general design principle for developing next-generation intelligent self-powered sensing systems.