Optical and charge transport properties of methylammonium versus triple-cation lead halide perovskites: a combined theoretical and experimental study

We investigate the optical and transport properties of two widely used perovskite materials for solar cells, methylammonium lead iodide (MAPI) and triple-cation perovskite (TriLHP), using first-principles calculations. Our theoretical results, supported by ellipsometry measurements, show that MAPI exhibits stronger dielectric screening and better absorption characteristics, which could contribute to enhanced defect tolerance and less sensitivity to light intensity fluctuations. In contrast, TriLHP demonstrates a lighter electron effective mass, attributed to halogen mixing and octahedral distortions, potentially improving electron mobility. We also estimate the exciton binding energy and radius for both materials, confirming their behavior as Wannier-Mott excitons. These findings provide critical insights into the material properties that govern the performance of perovskite solar cells.