ZnO‐Based Photomultiplication‐Type Infrared Photodetectors for Ultrasensitive Upconverters

Abstract High‐sensitivity infrared photodetectors have attracted attention due to their broad applications. Photomultiplication is an ideal choice for high‐sensitivity photodetectors since it can generate large photogenerated current under incident faint illumination, making them more user‐friendly and cost‐effective without any extra amplifier circuits. In this work, 2 wt.% acetic acid in methanol is optimized to treat the electron‐accumulated ZnO layer in photodetector ITO/ZnO/PbS/Ag by increasing its interfacial oxygen vacancies, thus the interfacial band bends at the ZnO/PbS interface due to the accumulated charges under illumination. In this way, a high‐gain photomultiplication‐type photodetector ITO/ZnO/PbS/Ag, in which PbS colloidal quantum dots (CQDs) act as the active layer, is presented. As a result, a high responsivity of 524 A/W with a high external quantum efficiency of 66516% is achieved from the photodetector ITO/ZnO/PbS/Ag under 0.2 µW cm −2 980 nm illumination at ‐1 V. Further, a low turn‐on voltage of 2 V is obtained from the upconverters ITO/ZnO/PbS(240 nm)/TAPC(50 nm)/CBP:Ir(ppy) 3 (60 nm)/BCP(20 nm)/LiF(1nm)/Al under 1.637 mW cm −2 980 nm illumination, exhibiting a photon‐to‐photon conversion efficiency of 11.08%. In addition, upconversion imaging through a single‐pixel device and a 16 × 16 display array is demonstrated, implying its potential scalable applications. Therefore, it provides a promising and applicable pathway for high‐performance upconverters.