Structure Stability and Optical Response of Lead Halide Hybrid Perovskite Photovoltaic Materials: A First-Principles Simulation Study

A third-generation of solar cell is based on organic-inorganic hybrid perovskite materials. These have reached up to 22.1% conversion efficiency through exponential growth just within the last decade, compared to much longer improvement times for other photovoltaic technologies. Lead halide perovskites are among the most commonly used materials in this context. Despite the relatively large number of available works on some of these materials, in particular CH3NH3PbI3, others are less investigated. Here, we focused on CH3NH3PbCl3, CH3NH3PbBr3 and CH3NH3PbI3 for assessing structure stability and optical response. Using quantum-mechanics-based first principles approaches, we calculated the optimized structures of these three materials in their cubic phase, followed by their optical response. Structure characteristics including geometrical features, energetics and phonon dispersions were presented and analyzed. Electronic structure calculations and resultant optical characteristics including real and imaginary dielectric constants, refractive index and absorption coefficient were calculated and discussed. Our results showed different stability characteristics for the three structures inferred from cohesive energy and phonon dispersion. The bromide and chloride materials showed narrower ranges of functional optical frequencies compared to iodide one. However, the former two materials showed increased dielectric constant, refractive index and absorption at lower wavelength compared to those of the latter, indicating possibly better photovoltaic performance at those wavelengths. The results could be useful in feasibility assessments of lead halide hybrid perovskite photovoltaic materials