Methylammonium lead halide perovskites: Electronic structure and optical properties for tandem solar cells

Solar cells based on tandem structures enable improved utilization of the solar spectrum and higher power conversion efficiencies. In this context, Methylammonium lead halide perovskites remain strong candidates for forming stacked configurations on silicon substrates. These perovskites, hereafter referred to as MALH, have the chemical formula CH3NH3PbX3, where X denotes a halide ion such as Bromine, Iodine or Chlorine. They are highly effective at converting sunlight into electrical energy due to their strong light absorption properties. In this work, a systematic comparative study of the three halide compositions (X = I, Br and Cl) in orthorhombic phase is carried out, in order to clarify the effect of halide substitution on the electronic structure and optical properties of these materials. Their structural, electronic and optical properties are theoretically investigated using first principles density functional theory (DFT) calculations. Analysis of the calculated density of states (DOS) and band structure confirms the direct band-gap nature of the perovskites, tunable around 1.64 eV for X=I, 2.43 eV for X=Br, and 2.50 eV for X=Cl. These results align well with previously reported experimental and theoretical finding, confirming the potential of these materials for future generation photovoltaics.