Three in One: A Versatile p‐i‐n Heterojunction Diode Based on Quasi‐2D Perovskite as a Solar Cell, Red Light Emitting Device and Weak Light Photodetector

Abstract Quasi‐two‐dimensional (Q‐2D) Ruddlesden‐Popper (RP) perovskites are rapidly developed for photoelectric device applications due to their unique multiple quantum‐well structures and adjustable photoelectric properties. Here, a three‐in‐one multifunctional photoelectric device that integrates photovoltaic (PV), electroluminescence (EL), and photodetection performance based on Q‐2D perovskite, which has not yet been reported, is explored and realized. As a solar cell (SC) mode under standard air mass 1.5G illumination, the optimal device has a power conversion efficiency (PCE) of 10.36%; as a light emitting diode (LED) mode under forward bias, the optimal device emits red light at 753 nm and achieves an EL external quantum efficiency (EQE_EL) of 0.42%; as a photodetector (PD) mode under a pulsed laser (660 nm), the optimal device exhibits superior weak‐light detection, with a linear dynamic range (LDR) improvement as wide as 161.8 dB, a high detectivity (D*) of 7.88 × 10¹² Jones, a fast rise/fall time of 19.1/35.2 µs and excellent stability. This work is of great significance to enrich the physical connotation and comprehensively improve the use efficiency of the multifunctional device.