On the photoresponse regulations by deep-level traps in CsPbBr₃ single crystal photodetectors

The all-inorganic halide perovskite CsPbBr₃ has attracted significant attention owing to its excellent opto-electronic properties. However, deep-level traps within the material are significant for the properties of CsPbBr₃ based opto-electronic devices. In this study, the effects of deep-level traps on the photoresponse characteristics of CsPbBr₃ photodetectors were thoroughly studied. By tailoring the illumination combinations where 532 nm light emitting diode (LED) illumination corresponds to the band-to-band excitation of photo-carriers and 648 nm LED illumination corresponds to sub-band excitation by the deep-level traps, it is proven that the device photoresponse performance is improved by the existence of deep-level traps. The photoresponsivity was enhanced by ∼63.64% (from 0.44 to 0.72 A W⁻¹) under 3.18 μW cm⁻² 532 nm LED illumination. The rise/fall time was reduced by 21.95% (from 20.5 to 16.0 ms)/25.47% (from 21.2 to 15.8 ms). The underlying physical mechanisms of deep level trap-induced modulations on the photoresponse performance of the CsPbBr₃ photodetector were revealed and discussed. By further systematic simulation of the effects of material properties on the photoresponse regulation, it was concluded that a shorter carrier lifetime, higher carrier mobility, higher trap concentration, and deeper trap level could improve the photoresponse of the CsPbBr₃ photodetector. This study aims to clarify the physical relation between material properties and device performance and provide guidance for high-performance CsPbBr₃ photodetector design.