Engineering optoelectronic properties of the Pb-free perovskite FASiBr3 − XIX (X = 0, 1, 2 or 3) for photovoltaic applications: first principle analysis

Abstract Lead-free perovskites have become a potential candidate for the development of the photovoltaic field. Here, we explored the structural and optoelectronic characteristics of silicon-perovskite FASiBr 3 − X I X ( X = 0, 1, 2 or 3) for solar device applications. Density functional theory has been applied. The band structure shows that FASiBr 3 FASiBr 2 I, FASiBrI 2 and FASiI 3 have a semiconductor nature with a direct band gap of (2.09 eV) (2.60 eV) PBE(HSE), (1.90 eV) (2.38 eV) PBE(HSE), (1.71 eV) (2.12 eV) PBE(HSE) and 1.60 eV (2.08) PBE(HSE), respectively. In addition, the studied perovskites also exhibited great optical properties including, high absorption; moreover, we showed that the substitution of Br by I in FASiBr 3 perovskite can considerably enhance the optical behavior. The dielectric function showed that the edge of absorption of Br-substituted I in FASiBr 3 perovskite was shifted towards the low energy zone (red-shift) compared to FASiBr 3 . As a result, FASiI 3 experiences greater absorption capability than its FASiBr 3 counterpart. These analyses indicate that FASiI3 is the best candidate for use as a Pb-free material for perovskite solar cells. Graphical abstract