Toward High-Performance Self-Powered Near-Ultraviolet Photodetection by Constructing a Unipolar Heterojunction

Constructing a unipolar heterojunction is an effective energy band engineering strategy to improve the performance of photoelectric devices, which could suppress dark current and enhance detectivity by modulating the transfer of carriers. In this work, unipolar heterojunctions of Si/PbI₂ and GaSb/PbI₂ are constructed successfully for high-performance self-powered near-ultraviolet photodetection. Owing to the unique band offset of unipolar heterojunctions, the transport of holes is blocked, and only photogenerated electrons in PbI₂ can flow unimpeded under the driving force of the built-in electric field. Thus, the recombination of photogenerated electron-hole pairs is suppressed, contributing to high-performance near-ultraviolet photodetection. The as-fabricated Si/PbI₂ self-powered near-ultraviolet photodetector exhibits a low dark current of 10^-13 A, a high I_light/I_dark ratio of 10⁴, and fast response times of 26/24 ms, which are much better than those of the PbI₂ metal-semiconductor-metal photodetector. Furthermore, the as-fabricated GaSb/PbI₂ unipolar heterojunction photodetector also exhibits impressive self-powered near-ultraviolet photodetection behaviors. Evidently, this work shows the potential of unipolar heterojunctions for next-generation Si-based and GaSb-based high-performance photodetection.