Relationships between distortions of inorganic framework and band gap of layered hybrid halide perovskites

TL;DR

This study systematically analyzes how various structural distortions in layered hybrid halide perovskites influence their band gaps, using DFT and machine learning to enable targeted material design.

Contribution

It quantitatively links inorganic framework distortions to band gap variations and employs inverse design to find structures with desired electronic properties.

Findings

Distortion of interlayer distance has the greatest impact on band gap.

Structures with different distortions can have similar band gaps.

Machine learning combined with DFT enables targeted band gap design.

Abstract

The unprecedented structural flexibility and diversity of inorganic frameworks of layered hybrid halide perovskites (LHHPs) rise up a wide range of useful optoelectronic properties thus predetermining the extraordinary high interest to this family of materials. Nevertheless, the influence of different types of distortions of their inorganic framework on key physical properties such as band gap has not yet been quantitatively identified. We provided a systematic study of the relationships between LHHPs' band gaps and six main structural descriptors of inorganic framework, including interlayer distances (dint), in-plane and out-of-plane distortion angles in layers of octahedra ({\theta}in,{\theta}out), layer shift factor (LSF), axial and equatorial Pb-I bond distances (dax,deq). Using the set on the selected structural distortions we realized the inverse materials design based on multi-step DFT and machine learning approach to search LHHPs with target values of the band gap. The analysis of calculated descriptors band gap dependences for the wide range of generated model structures of (100) single-layered LHHPs results in the following descending order of their importance:dint > {\theta}in > dax > LSFmin > {\theta}out > deq > LSFmax, and also implies a strong interaction value for some pairs of structural descriptors. Moreover,we found that the structures with completely different distortions of inorganic framework can have similar band gap, as illustrated by a number of both experimental and model structures.