Design Insights and Photovoltaic Performance Analysis of Non-Lead Inorganic RbSnX₃ (X = I, Br, Cl) Perovskites through Coupled Density Functional Theory and SCAPS-1D Simulation Frameworks

Abstract

The development of lead (Pb)-free perovskite solar cells (PSCs) addresses the stability, commercialization, environmental, and health challenges associated with Pb-based PSCs. In the current research, Pb-free rubidium (Rb)-based perovskites RbSnX 3 (X = I, Br, Cl) were investigated through density functional theory (DFT) using the WIEN2K code and SCAPS-1D tool for analysis of photovoltaic (PV) applications. We computed the optoelectronic and structural properties of cubic phase RbSnX 3 (X = I, Br, Cl) perovskites (PVSKs). The DFT-computed band gap (E g ) of RbSnI 3 , RbSnBr 3 , and RbSnCl 3 were found to be 0.67, 1.28, and 1.53 eV, respectively, using the TB-mBJ exchange-correlation potential. The obtained E g of RbSnI 3 is very small, and is not suitable for solar cell (SC) applications. On the other hand, the E g values of RbSnBr 3 and RbSnCl 3 PVSKs are suitable for SC applications due to their closeness to the ideal E g of 1.45 eV, as predicted by the Shockley− Quiesser limit of theoretical efficiency. Therefore, we investigated the PV performance of RbSnBr 3 and RbSnCl 3 using SCAPS-1D software. The optical and electronic properties of cubic RbSnX 3 (X = Br, Cl) used as an absorber in PSCs extracted from DFT, have been used for the simulation. We varied the perovskite layer parameters to achieve the optimal performance for PSCs. We simulated RbSnX 3 (X = Br, Cl)-based PCS with several hole-transport layers (HTLs) and electron-transport layers (ETLs). Titanium dioxide (TiO 2 ) as the ETL and poly(triarylamine) (PTAA) as the HTL exhibited best performance among different combinations. The PSC structure fluorine-doped tin oxide (FTO)/TiO 2 /RbSnBr 3 /PTAA/Au delivered a PCE of 22.53%, J SC of 35.05 mA/cm 2 , V OC of 0.78 V, and FF of 73.06%, while FTO/TiO 2 /RbSnCl 3 /PTAA/Au exhibited a PCE of 22.64%, J SC of 26.63 mA/cm 2 , V OC of 1.08 V, and FF of 78.17%. The remarkable ability of RbSnX 3 (X = Br, Cl) PVSKs to capture photons efficiently and effectively can help in the development of PV and optoelectronic devices.