NIR to Visible Light Upconversion Devices Comprising an NIR Charge Generation Layer and a Perovskite Emitter

Abstract Near‐infrared (NIR) to visible light upconversion is of significant importance in many applications, including thermal imaging, bioimaging, night vision, and wellness monitoring. Here, the effort to develop a high‐performing NIR to saturated green light upconversion device comprising a front solution‐processable organic bulk heterojunction NIR charge generation layer (CGL) and an upper CsPbBr₃ perovskite light‐emitting diode (LED) unit is reported. The NIR CGL, based on a blend of the NIR‐sensitive donor polymer and a nonfullerene acceptor, enables an efficient hole injection in the CsPbBr₃ LED in the presence of the NIR light and also serves as an optical outcoupling layer to enhance the visible light emission by the CsPbBr₃ LED. The CsPbBr₃‐based perovskite LED has a narrow emission spectrum with a peak wavelength of 520 nm, corresponding to the wavelengths near the peak response of the human eye, and has the advantage in imaging applications. Based on the upconversion process, a pixel‐less NIR to visible light imaging device is demonstrated, which can be operated at a low voltage of 3 V. The results are very encouraging, revealing a high‐performing solution‐processable upconversion device for application in NIR light imaging.