High-performance photodetectors based on CsSnBr₃/Si PN heterojunction by pulsed laser deposition epitaxy

Abstract

Halide perovskite semiconductors have outstanding physical properties such as high light absorption coefficient, large carrier diffusion length, and high photoluminescence quantum efficiency, and demonstrate significant potential in optoelectronic devices such as photodetectors and solar cells. However, the toxicity and environmental instability associated with lead-based perovskites significantly limit their applications. Substituting tin with lead in perovskites and growing high-quality tin-based perovskite films present an attractive solution. In this study, we adopted the pulsed laser deposition method to achieve the epitaxial growth of CsSnBr₃ films on silicon substrates. The morphology, optical and electrical properties of the CsSnBr₃ films, as well as the CsSnBr₃/Si heterojunction detectors, were comprehensively investigated with various characterization techniques, including XRD <i>2θ</i>-<i>ω</i> and <i>φ</i> scans, atomic force microscope, scanning electron microscope, photoluminescence and time-resolved photoluminescence spectroscopy, and Hall electrical measurements. The results indicate that such CsSnBr₃ film grows epitaxially onto the silicon substrate via a face-to-face mode. Interestingly, an unusual temperature-dependent bandgap increase was found due to the high electron effective mass of CsSnBr₃. The CsSnBr₃ film demonstrated P-type semiconductor behavior with a high mobility of 122 cm²/(V∙s), enabling the formation of an ideal Type-II heterojunction with the silicon substrate. The CsSnBr₃/Si semiconductor heterojunction detectors exhibited distinctive heterojunction PN diode characteristics in the dark and a pronounced photoresponse under illumination. At zero bias, the detectors displayed a switch ratio exceeding 10⁴, responsivity of 0.125 mA/W, external quantum efficiency of 0.0238 %, detectivity (D*) of 2.1×10⁹ Jones, and response/recovery times of 3.23/4.87 ms. Under a small bias of -1 V, the switch ratio decreased to 50, but responsivity and external quantum efficiency increased by 568 times. The detectors can maintain self-powered operation state with high switch ratio (10⁴) and millisecond-level response/recovery times. In conclusion, this work presents a self-powered, high-performance photodetector based on CsSnBr₃ epitaxial films integrated with silicon substrates.