Reducing Pb concentration in α-CsPbI₃ based perovskite solar cell materials via alkaline-earth metal doping: A DFT computational study

Full inorganic perovskite solar cell materials have shown significantly improved performance in recent years. To reduce their reliance on Pb, alkaline-earth metal ions (Ba, Sr, Ca, and Mg) have been employed for the exchange of Pb in α-CsPbI₃. In this study, density functional theory calculations were used to study the structures, band structures, and optical absorption properties of these alkaline-earth-metal doped α-CsPbI₃ materials with CASTEP (2017) and Dmol³ (2017). The calculation also investigated the effect of spin-orbit coupling. Alkaline-earth metal doping can enlarge the band gap of α-CsPbI₃ and convert α-CsPbI₃ from a direct gap semiconductor to an indirect gap semiconductor. After alkaline-earth metal doping, the sun-light absorption increased. Among all the alkaline-earth metals studied here, Mg-doped α-CsPbI₃ showed the most improved indirect gap band structure, ideal band gap (compared to α-CsPbI₃), and sun-light absorption.