Hybrid metal halide perovskites: optoelectronic properties and stability (Conference Presentation)

Abstract

Hybrid metal halide perovskites (stoichiometry AMX3) have recently emerged as low-cost active materials in PV cells with power conversion efficiencies in excess of 21%. We discuss how parameters essential for photovoltaic operation, such as crystallinity, photostability, charge carrier mobility and diffusion lengths are altered with substitutions of the organic A cation (e.g. methylammonium versus formamidinium), the metal M cation (e.g. Pb2+ or Sn2+) and the halide X anion (I- versus Br-). We focus on two 3D perovskite systems that have attracted interest lately, lead-free ASnI3 (optical bandgap ~1.3 eV) and the mixed organic lead iodide/bromide system APb(BryI1-y)3 whose band gap can be tailored between ~1.5 eV (FAPbI3) and ~2.3 eV (FAPbBr3). We show that unintentional hole doping in tin iodide perovskites introduces fast recombination pathways that can be moderated by crystal structure [1] and introduces a radiative quasi-monomolecular charge recombination channel [2]. In addition, we demonstrate that charge-carrier diffusion and recombination in FA1-xCsxPb(BryI1-y)3 depends on a complex interplay between changes in morphology and electronic bandstructure with bromide fraction y [3,4,5].