Spontaneously Formed PbS Colloidal Quantum Dot Microstructures Make for High‐Performance Top‐Illuminated Short‐Wave Infrared Imager

A high‐performance top‐illuminated short‐wave infrared (SWIR) imager is achieved based on the solution‐processed PbS colloidal quantum dot (CQD) photodiodes, by introducing the spontaneously formed PbS microstructures on the active layer through managing the CQD packing manner simply by appropriate solvent selection. The presence of the PbS microstructures simultaneously serves the following two vital functions. The first is to exert the light trapping effect for higher photon absorption, as well as decrease trap states for inhibiting the trap‐assisted recombination of photogenerated carriers, both promoting the photoresponsivity in the SWIR region. The second is to remove surface cracks on the CQD films for reducing the defect‐induced current leakage paths, as well as reducing the trap‐assisted tunneling current, thereby suppressing reverse bias dark current density ( J dark ). The top‐illuminated PbS CQD photodiodes reach a high photoresponsivity of 0.38 A W −1 at 1413 nm and a low J dark of 8.2 ×10 −8 A cm −2 at –1 V, which is among the best photodetection performances reported for top‐illuminated CQD SWIR photodiodes. Such SWIR photodiodes are integrated with the thin‐film transistors to produce a top‐illuminated imager with 64 × 64 pixels, which demonstrates excellent SWIR imaging performance. This work opens up an intriguing shortcut toward low‐cost, low‐noise, and high‐sensitivity SWIR imaging.