Abstract
Hybrid organic–inorganic perovskites have been one of the most active areas of research into photovoltaic materials. Despite the extremely fast progress in this field, the electronic properties of formamidinium lead iodide perovskite (FAPbI3) that are key to its photovoltaic performance are relatively poorly understood when compared to those of methylammonium lead iodide (MAPbI3). In this study, first-principles total energy calculations based on density functional theory were used to investigate the favored orientation of FA. Different theoretical methods, with or without incorporation of spin-orbit coupling (SOC) effects, were used to study the structure, electronic properties, and charge-carrier effective mass. Also the SOC-induced Rashba k-dependent band splitting, density of states and optical properties are presented and discussed. These results are useful for understanding organic–inorganic lead trihalide perovskites and can inform the search for new materials and design rules.
Highlights
Hybrid organic–inorganic perovskites have found prominence as a material for the active photovoltaic layer in optoelectronic devices due to their high and balanced charge-carrier mobilities, suitable band gaps, and high absorption cross sections.[1,2,3] The most studied organic–inorganic lead trihalide perovskites have the general composition APbX3, where A 1⁄4 methylammonium (MA), formamidinium (FA), or Cs, and X 1⁄4 I, Br, or Cl
MAPbI3 is the most studied hybrid metal-organic perovskite for photovoltaic applications, better performance in terms of photovoltaic efficiency is found in FAPbI3 or mixed FA and MA hybrid perovskites.[5,6,7]
The ground state of FAPbI3 with a h111i orientation was the most stable, which is consistent with the results of calculations with the MA cation in the ground state of MAPbI3, due to the organic molecule being oriented in the h111i direction, where it has maximum freedom.[32,33]
Summary
There have been extensive theoretical works studying the structure and electronic, optical, and defect properties of MAPbI3, and these have greatly deepened the understanding of MAPbI3 and accelerated research into its application to devices.[14,15,16,17,18,19] there have been some of theoretical works studying FAPbI3,20–24 a systematic and comprehensive study is still absent. By using the rst-principles total energy calculation method, we systematically investigated the structure, electronic properties, charge effective mass, k-dependent band splitting and optical properties of cubic a-FAPbI3. Different calculation methods were evaluated, speci cally, standard density functional theory (DFT), screened hybrid DFT, and the GW approach, both with and without incorporation of spin-orbit coupling (SOC) effects. The transport properties of the charge effective mass and the optical properties are given and discussed
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