# Structural and Electronic Reconstruction of Extended Defects in Pnictogen Chalcohalides

## TL;DR

This paper explores how pnictogen chalcohalide materials can resist defects that usually harm solar cell performance, making them promising for renewable energy.

## Contribution

The study predicts structural and electronic reconstructions in pnictogen chalcohalides that eliminate harmful defects using density functional theory.

## Key findings

- Surface reconstructions in pnictogen chalcohalides eliminate detrimental gap states despite bond cleavage.
- New interchain bonds at the surface preserve electronic performance and resilience to extended defects.
- Pnictogen chalcohalides are identified as defect-tolerant candidates for thin-film photovoltaic absorbers.

## Abstract

With growing global demand for renewable energy, thin-film
photovoltaic
technologies are emerging as a promising route to low-cost, scalable
solar power. However, for many candidate materials extended defects
in polycrystalline thin films are associated with deep gap states
that limit carrier lifetimes and reduce device efficiency. Pnictogen
chalcohalide semiconductors with the general formula MChX (M = pnictogen,
Ch = chalcogen, X = halogen) have been proposed as defect-tolerant
alternatives. Using density functional theory, we predict the structure
and electronic properties of surface defects for eight pnictogen chalcohalide
compounds and analyze their behavior upon surface reconstruction.
Our results reveal that, despite the cleavage of covalent bonds, these
materials undergo reconstructions that eliminate detrimental gap states.
The facile formation of new interchain bonds at the surface preserves
the electronic performance of the materials and suggests intrinsic
resilience to extended defects. These findings position pnictogen
chalcohalides as promising candidates for defect-tolerant, stable,
thin-film photovoltaic absorbers.