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 − XI_X (X = 0, 1, 2 or 3) for solar device applications. Density functional theory has been applied. The band structure shows that FASiBr₃ FASiBr₂I, FASiBrI₂ and FASiI₃ 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 FASiBr₃ perovskite can considerably enhance the optical behavior. The dielectric function showed that the edge of absorption of Br-substituted I in FASiBr₃ perovskite was shifted towards the low energy zone (red-shift) compared to FASiBr₃. As a result, FASiI₃ experiences greater absorption capability than its FASiBr₃ counterpart. These analyses indicate that FASiI3 is the best candidate for use as a Pb-free material for perovskite solar cells.

Graphical abstract