Non-toxic FASnI₃ perovskite on nanostructured black silicon for light-trapping-enhanced infrared photodetection

Lead(Pb)-based perovskites have exhibited exceptional light absorption characteristics and superior photoconversion efficiencies in optoelectronic applications but face commercialization limits due to Pb toxicity and chemical instability. Tin(Sn)-based perovskites, particularly formamidinium tin triiodide (FASnI₃), have emerged as promising non-toxic alternatives for infrared (IR) photodetection. Here, we fabricate FASnI₃ thin films on nanostructured black silicon (b-Si) substrates and compare with films on flat silicon (f-Si) substrates to systematically evaluate their IR photodetector performance, including responsivity, detectivity, and external quantum efficiency (EQE). The b-Si based devices yield a response speed approximately 20 times faster than that of f-Si, driven by enhanced light trapping at the nanostructured surface that boosts photon absorption and carrier generation, alongside 2 times higher detectivity depending on incident optical power. Time-dependent PL results suggest a modest substrate-enabled mitigation of ambient degradation trends. These substrate-dependent improvements in performance highlight b-Si as a viable platform for realizing non-toxic perovskite IR photodetectors.