Defect suppression and photoresponsivity enhancement in methylammonium lead halide perovskites by CdSe/ZnS quantum...

Potential strategies such as surface passivation and perovskite material halide mixing may protect material surfaces, improve luminescence, and reduce charge traps for device stability. In this study, we used deep level transient spectroscopy to investigate the effect of CdSe/ZnS core-shell quantum dots (QDs) on defect states and carrier transport in methylammonium (MA) lead halide perovskites (CH₃NH₃PbX₃ where X  = I, Br). In MAPbI₃ and MAPbI₂Br films with CdSe/ZnS QDs, the density of hole traps located at E_v + 0.37 eV and E_v + 0.56 eV was reduced dramatically. Deep traps at E_v + 0.78 eV and E_v + 1.08 eV were removed, and one broad electron trap signal dominated. Film photoresponsivity under 600-nm wavelength light and a bias voltage of -0.7 V was 10 and 18 mA/W, which is 100 and 27 times larger than the 0.1 and 0.67 mA/W of bare perovskites (PS), respectively. This demonstrates that carrier transport was enhanced due to defect suppression. Our findings on defect suppression and photoresponsivity enhancement provide an important direction for optimizing high-performance PS device fabrication.