Nonlayered In₂S₃/Al₂O₃/CsPbBr₃ Quantum Dot Heterojunctions for Sensitive and Stable Photodetectors

Two-dimensional (2D) materials have attracted widespread research attention toward multiple optoelectronic applications, owing to their promising sensitivity to light. However, the weak light absorption and the insufficient effective photoconductive gain mechanism severely limit the performance of photodetectors based on 2D materials. Herein, by integrating the 2D In2S3 channel, Al2O3 tunneling layer, and CsPbBr3 photoactive layer, an ultrasensitive photodetector is demonstrated. The CsPbBr3 layer is exploited as an efficient light absorber and the component for the construction of type-II band arrangement with In2S3. The interlayer carrier coupling is blocked, and the spatial separation of photoinduced carriers is realized through quantum tunneling. In this respect, photoinduced holes are captured in CsPbBr3, accompanied with electrons recycled in In2S3, from which a high photoconductive gain is accomplished. Eventually, in detail, a responsivity of up to 2812 A/W, short rise/decay time of 144/32 μs, and excellent detectivity of 2 × 1015 Jones are assembled, reaching one of the best parameters of photodetectors based on 2D materials. Moreover, this vertical device structure enables the complete encapsulation of unstable CsPbBr3 by In2S3/Al2O3, preventing the cleavage of Pb–Br bonds in normal ambient conditions. This study provides a strategy to enhance the performances of the hybrid photodetector, along with the demonstration of important insights into advanced device designs for achieving high-performance optoelectronic devices.