# Electronic and gap properties of lead-free perfect and mixed hybrid halide perovskites: An \textit{ab-initio} study

## TL;DR

This study uses extit{ab-initio} calculations to explore lead-free hybrid halide perovskites, identifying promising compounds with tunable band gaps suitable for optoelectronic applications.

## Contribution

It introduces a comprehensive extit{ab-initio} analysis of various MABX$_3$ compounds, highlighting potential lead-free alternatives to MAPbI$_3$ with comparable electronic properties.

## Key findings

- Certain compounds like MAZnCl$_3$, MACdBr$_3$, MAGeCl$_3$, MAGeBr$_3$ have similar band gaps to MAPbI$_3$.
- Band gaps can be tuned in mixed halide perovskites without a simple pattern.
- The study suggests new lead-free materials for optoelectronic devices.

## Abstract

Hybrid halide perovskites are currently under intense investigation due to their potential applications in optoelectronics and solar cells. Among them, MAPbI$_3$ where MA stands for the methylammonium cation, exhibits ideal properties for solar cells. In attempt to identify new lead-free halide perovskites we have studied using \textit{ab-initio} electronic structure calculations in conjunction with hybrid functionals a series of MABX$_3$ compounds where B is a divalent cation and X a halogen atom. Our results suggest that the compounds under study exhibit a variety of lattice constants and energy band gaps. Especially, MAZnCl$_3$, MACdBr$_3$, MAGeCl$_3$ and MAGeBr$_3$ are susceptible to replace MAPbI$_3$ in devices since they show comparable energy gaps. Further calculations on the mixed hybrid halide perovskites show that we can tune the values of the energy gap although no simplified pattern exists. Our results pave the way for further investigation on the use of these materials in technology relevant applications.