Asymmetric contact enabled self-powered flexible photodetector utilizing formamidinium-based perovskite with a 2D MXene electrode

Abstract

Self-powered photodetectors (PDs) are very important for next-generation optoelectronic applications, including wearable electronics, optical communication, wireless sensing, and biomedical imaging. Hybrid lead halide perovskites have emerged as promising materials for high-performance PDs with their exceptional performance matrices and simple fabrication method. On the other hand, two-dimensional Ti₃C₂T_x MXene has received wide attention as an additive, charge transfer layer, and conductive electrode for optoelectronic applications due to its outstanding properties. In this study, we present a highly sensitive visible-light PD utilizing a formamidinium-cesium (FACs) perovskite (PVK) thin film, integrated with an asymmetric MXene (MX) – silver (Ag) electrode featuring different work functions to enhance the charge carrier separation. The device exhibits a high photoresponsivity of 2.58 A W⁻¹ and detectivity of 1.013 × 10¹³ Jones. Under self-bias configuration, it achieves a remarkable responsivity of 160 mA W⁻¹, detectivity of 2.63 × 10¹² Jones, and external quantum efficiency of 49%, making it highly attractive for energy-efficient photodetection. The superior performance arises from an engineered built-in electric field at the asymmetric MX–PVK–Ag junction, which effectively separates electron–hole pairs and ensures unidirectional charge flow under illumination. Furthermore, a flexible PD is fabricated, which retains excellent photoresponse and exhibits outstanding mechanical flexibility under repeated bending. Density functional theory (DFT) calculations reveal efficient charge transport across the local Schottky junction and ultraviolet photoelectron spectroscopy (UPS) explains the interfacial band alignment and charge transfer dynamics across the two interfaces in the PD. Combining high sensitivity, self-powered operation, and a simple device architecture, the as-fabricated PD emerges as a promising candidate for next-generation low-power photodetection systems.