Broadband, High-Performance, and Self-Powered Photodetector Based on a Bi ₂ O ₂ Se/CdSe Vertical Type-II Heterojunction

Photodetectors based on Bi<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Se currently suffer from low responsivity, limited detection sensitivity, and insufficient broadband photoresponse capability, which significantly hinders their practical application in high-performance optoelectronic devices. To overcome these limitations, this study designs and fabricates a broadband (300–1300 nm), high-performance photodetector based on a vertically stacked Bi<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Se/CdSe heterojunction. Under 560 nm illumination and a 5 V bias voltage, the device exhibits a high responsivity of 6.18×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> A/W, an on/off ratio of 1.46×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup>, and a specific detectivity of 1.95×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> Jones. Remarkably, even under zero-bias conditions, the device maintains a responsivity of up to 1.99 A/W, a detectivity of 6.23×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> Jones, and an on/off ratio of 2.52×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, demonstrating outstanding self-powered characteristics. This work not only proposes an efficient strategy for constructing high-performance heterojunction that effectively break through the limitations of conventional photodetectors, but also elucidates the critical role of interfacial engineering in enhancing the self-driven behavior of the device, thereby providing a theoretical foundation and technical support for the development of low-power, high-performance photodetection systems.