High performance broadband photoelectrochemical photodetectors based on Cu-doped Bi ₂ O ₂ Se nanosheets

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.