Hybrid perovskites for photovoltaics: Insights from first principles

methylammonium lead iodide perovskites at the core of recently proposed solar cells with exceptionally large quantum conversion efficiency are studied by first-principles methods. Large absorption coefficients ( 0.030.04 nm(-1) for wavelength similar to 500 nm) and small effective masses suited for both n-type and p-type transport are obtained as a consequence of their peculiar structural and electronic characteristics. In particular, the presence of a direct gap between highly dispersed Pb( 6s)-I( 5(p)) valence bands and Pb( 6(p)) conduction bands is the key ingredient at the basis of their excellent performance in photovoltaic applications.