Large Photomultiplication by Charge-Self-Trapping for High-Response Quantum Dot Infrared Photodetectors

PbS colloidal quantum dots (CQDs) are emerging as promising candidates for next-generation, low-cost, and high-performance infrared photodetectors. Recently, photomultiplication has been explored to improve the detectivity of CQD infrared photodetectors by doping charge-trapping material into a matrix. However, this relies on remote doping that could influence carrier transfer giving rise to limited photomultiplication. Herein, a charge-self-trapped ZnO layer is prepared by a surface reaction between acid and ZnO. Photogenerated electrons trapped by oxygen vacancy defects at the ZnO surface generate a strong interfacial electrical field and induce large photomultiplication at extremely low bias. A PbS CQD infrared photodiode based on this structure shows a response (R) of 77.0 A·W^-1 and specific detectivity of 1.5 × 10¹¹ Jones at 1550 nm under a -0.3 V bias. This self-trapped ZnO layer can be applied to other photodetectors such as perovskite-based devices.