Enhancing the Performance of a Tin Halide Perovskite Photodetector through Trifluoromethyl Cation Passivation

The tin halide perovskites as a lead-free alternative for optoelectronics have attracted considerable attention due to their remarkable optoelectronic performance and reduced environmental toxicity. However, a major challenge remains regarding the stability issue, primarily due to the oxidation of Sn2+ to Sn4+ under ambient conditions, which leads to material degradation and poor long-term performance. Herein, we report the enhanced performance of the FASnI3 photodetector by incorporating 4-trifluoromethyl benzyl ammonium iodide (TFMBAI) into the precursor solution. Under a light intensity of 5 mW/cm2, the responsivity at 685 nm increases to 0.325 A·W–1, achieving an enhancement of nearly 57.5 times compared with the unmodified sample. Additionally, the device exhibits a broadband photoresponse ranging from 415 to 980 nm. By optimizing the addition of TFMBAI, we have reduced the proportion and defect states of Sn4+, successfully promoted the oriented crystal growth and passivated defects, and achieved a more stable, uniform, and pinhole-free perovskite film, thereby enhancing both carrier mobility and performance stability. Our results demonstrate the great potential of TFMBAI for applications in nontoxic and highly stable tin halide perovskite photodetectors.