Local Electrostatic Screening Enabled Ultrafast Bipolar Homojunction Photodiode Towards High Dynamic Range In-Sensor Image Processing

Abstract Capturing optical information while simultaneous in-sensor image processing shows great advantages on machine vision in terms of latency, energy efficiency and security. Particularly, high dynamic range (HDR) in-sensor imaging in challenging lighting conditions is crucial for open-world intelligent machine vision applications such as robotics, unmanned aerial vehicle and autonomous driving. The versatile photoresponse-turnabilities of two-dimensional (2D) semiconductors by electrostatic gating have shown promising pathway for the in-sensor visual processing. However, the limited linear dynamic range (LDR) of the photodetectors inhibits their implementation in HDR scenes. Here, we demonstrate that a single-gate-tunable bipolar photoresponse of tungsten diselenide (WSe₂) in-plane homojunction constructed through a facile, efficient and universal local electrostatic screening strategy, can perceive and process HDR images simultaneously. The showcase van der Waals stacking of WSe₂/PdSe₂ in-plane homojunction photosensors leveraging band-alignment exhibits an excellent performance with an ultrafast response time of 8 ns and a large physical LDR up to 144 dB. This large physical LDR allows the capture of HDR images with high precision, while the gate-tunable bipolar photoresponse enables in-sensor image processing. Our results provide an effective strategy for constructing photodetectors with tunable positive/negative responses and high LDRs, which are promising for in-sensor visual processing of scenes with HDR.