Decoupling the Trade‐Off Between the Photosignal and Photonoise in Upconversion Devices Through a Solution‐Processed Nickel Oxide Interconnecting Layer

Abstract Near‐infrared (NIR) to visible upconversion devices (UCDs) provide a viable and cost‐effective way for NIR visualization and pixel‐less imaging techniques. An excellent electrical connection between the NIR detection unit and the visible emission unit in the UCD is one of the prerequisites for achieving efficient upconversion performance. In this study, a low temperature‐ and solution‐processed nickel oxide (NiO_x) interconnecting layer (ICL) with high hole mobility and favorable energy levels is demonstrated to decouple the trade‐off between photosignal and photonoise in the UCDs. The use of such a NiO_x ICL suppresses intrinsic visible emission in the dark (photonoise) but enhances visible light output under NIR illumination (photosignal) by triggering an efficient charge injection in the UCDs. As a result, a hybrid UCD monolithically integrating an organic NIR photodetector and a visible quantum dot light‐emitting diode via the NiO_x ICL achieves excellent performance, exhibiting an ultralow turn‐on voltage as low as 1.6 V, a high luminance close to 6.3 × 10³ cd m⁻², a wide operation voltage window up to 7.4 V, and a high contrast ratio reaching 5 × 10⁴. The resulting UCD is also used for imaging demonstrations showing clear visible images of the NIR targets, which paves the way for practical applications.