Multi-scale model for the structure of hybrid perovskites: Analysis of charge migration in disordered MAPbI$_3$ structures

TL;DR

This paper introduces a multi-scale model combining quantum mechanics and classical hopping to analyze how cation disorder affects charge mobility in hybrid perovskites, crucial for optimizing photovoltaic efficiency.

Contribution

It develops a novel multi-scale approach that links quantum calculations with coarse-grained models to study charge transport in disordered hybrid perovskites.

Findings

Charge mobility varies with structure, ranging from 50 to 66 cm²V⁻¹s⁻¹.

Ordered tetragonal phase exhibits the highest charge mobility.

Disorder in cation arrangement significantly impacts charge transport.

Abstract

We have developed a multi-scale model for organic-inorganic hybrid perovskites (HPs) that applies quantum mechanical (QM) calculations of small HP supercell models to large coarse-grained structures. With a mixed quantum-classical hopping model, we have studied the effects of cation disorder on charge mobilities in HPs, which is a key feature to optimize their photovoltaic performance. Our multi-scale model parametrizes the interaction between neighboring methylammonium cations (MA$^+$) in the prototypical HP material, methylammonium lead triiodide (CH$_3$NH$_3$PbI$_3$, or MAPbI$_3$). For the charge mobility analysis with our hopping model, we solved the QM site-to-site hopping probabilities analytically and computed the nearest-neighbor electronic coupling energies from the band structure of MAPbI$_3$ with density-functional theory. We investigated the charge mobility in various MAPbI$_3$ supercell models of ordered and disordered MA$^+$ cations. Our results indicate a structure-dependent mobility, in the range of 50$-$66 cm$^2$V$^{-1}$s$^{-1}$, with the highest observed in the ordered tetragonal phase.