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

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 FASiBr3 − XIX (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.