Impact of MAPbI 3 phase transitions on solar cell performance: Influence of the ab-initio approximations in device performance

This paper presents a first step toward a pragmatic phenomenological multiscale approach to evaluate perovskite solar cell performance which determines material properties at the atomistic scale with first-principles calculations, and applies them in macro-scale device models. This work focuses on the MAPbI 3 (MA = CH 3 NH 3 ) perovskite and how its phase transitions impact on its optical, electronic, and structural properties, which are investigated at the first-principles level. It is based on a nanoscale description of MAPbI 3 , which allows to take the MA ordering into account, used to determine a hybrid exchange-correlation functional optimized to yield qualitatively correct and quantitatively accurate description of the structural and electronic properties of this family of perovskite in good agreement with experiment. The calculated optical indices are in better qualitative agreement than the previously published ones based on a local description of the material determined with more sophisticated methods. The obtained optical indices, band gaps and affinities serve as input to a numerical drift-diffusion device model. This yields the performance of corresponding non optimized single junction devices, with a methodology aiming at evaluating the performance of these materials rather than modelling real efficiencies. The obtained results are systematically discussed in terms of atomic model and first-principles approximation, such as the spin-orbit coupling effects and other issues, which can lead to unphysical evaluation of the cell performance.