High performance broadband photoelectrochemical photodetectors based on Cu-doped Bi2O2Se nanosheets

Abstract

The two-dimensional material Bi₂O₂Se has emerged as a promising candidate for photoelectrochemical (PEC) applications due to its moderate bandgap, strong light–matter interaction, and excellent environmental stability. However, its practical application is limited by high carrier recombination rates and poor charge transport properties. To overcome these limitations, this study proposes a copper (Cu) doping strategy to modulate the band structure and interfacial kinetics. Cu-doped Bi₂O₂Se (CBOS) nanosheets were synthesized via a facile hydrothermal method. The resulting CBOS-based PEC photodetector achieves a photocurrent density of 28.46 μA cm⁻² under 365 nm illumination, representing a 7.9-fold enhancement over the undoped Bi₂O₂Se device, along with a responsivity of 10.78 mA W⁻¹ and a rapid response (rise and decay times of 60 ms). The device enables broad-spectrum detection from 365 to 700 nm in a self-driven mode (0 V bias), and its performance can be tuned by an external bias (up to 0.6 V) and electrolyte concentration. Remarkably, it retains 85% of its initial photoresponse after one month of storage, demonstrating outstanding stability. This study demonstrates the synergistic enhancement of light absorption, carrier transport, and photocurrent generation through elemental doping, providing a key proof of concept for the structural design and performance modulation of high-performance materials for PEC applications.