Defect-Mediated Exciton Dissociation in α-In ₂ Se ₃ for Photodetection with High-Efficiency Carrier Collection

Exciton dissociation is a crucial process for efficient photoelectric conversion and an effective means of optimizing the photodetection performance, acting as the bridge between light excitation and photocurrent generation. In contrast to traditional interface engineering methods, defect-mediated modulation offers an intrinsic approach to influencing exciton dynamics by modifying local electronic structures. In this work, we control the formation of Se-related defects in α-In2Se3 through oxygen plasma treatment and analyze both temperature-dependent and laser power-dependent photoluminescence spectra, demonstrating that the intentionally introduced vacancies in α-In2Se3 could promote exciton dissociation and generate free carriers. In addition, the dynamic competition between carrier generation, recombination, and transport is unveiled by designing device configurations. A defect-engineered homojunction model is then constructed to further optimize the charge separation process, which exhibits excellent photodetection performance, with a high responsivity of 6.37 × 104 A W–1, a linear dynamic range of 95.8 dB, and a 42-fold increase in the light on/off ratio compared to the pristine device. At last, the potential of using the α-In2Se3 homojunction device as a full-color imager is illustrated. This work offers a strategic approach by defect engineering for high-efficiency carrier collection in two-dimensional optoelectronic devices.