First-principles insight into the structural and optoelectronic properties of Sn- and Pb-based hybrid halide perovskites for photovoltaic applications

In this work, we have theoretically investigated structural and optoelectronic properties of Sn and Pb halide perovskites incorporating trimethylammonium (TMA+) organic cation by employing density functional theory formalism. Here, our focus is to devise less toxic, efficient and stable perovskite materials for application in photovoltaics. From the calculation of formation energy (ΔE) and tolerance factor, it is found that both TMAPbX3 and TMASnX3 exhibit structural and thermal stability. From the observed band gap values and Bader charge analysis, it can be inferred that halide ions play an important role in tuning the electronic properties of the designed Organic inorganic hybrid halide perovskite (OIHP) materials. Our results also reveal that compounds with I− ion possess lower value of fundamental band gap and higher thermal stability. Reorganisation energies indicate that our designed compounds will predominantly act as hole transporting material. The calculated theoretical power conversion efficiency (η) indicates that TMASnI3 may act as an alternative material for Pb-based perovskite materials. Moreover, TMASnX3 shows strong absorption in the visible range of electromagnetic spectrum therefore, it is imperative to replace Pb by Sn to fabricate less toxic OIHP material.