# Electronic Properties, Screening and Efficient Carrier Transport in NaSbS2

## TL;DR

This study uses first principles calculations to analyze NaSbS2, revealing its electronic structure, anisotropic properties, and defect tolerance, which explain its effectiveness as a solar absorber.

## Contribution

It provides detailed theoretical insights into NaSbS2's electronic and optical properties, highlighting features that contribute to its defect tolerance and charge collection efficiency.

## Key findings

- Indirect and direct band gaps are close, reducing recombination.
- Highly anisotropic electronic and optical properties.
- Enhanced defect tolerance due to local screening from hybridization.

## Abstract

NaSbS2 is a semiconductor that was recently shown to have remarkable efficacy as a solar absorber indicating efficient charge collection even in defected material. We report first principles calculations of properties that show (1) an indirect gap only slightly smaller than the direct gap, which may impede recombination of photoexcited carriers, (2) highly anisotropic electronic and optical properties reflecting a layered crystal structure, (3) a pushed up valence band maximum due to repulsion from the Sb 5s states and (4) cross-gap hybridization between the S p derived valence bands and the Sb 5p states. This latter feature leads to enhanced Born effective charges that can provide local screening and therefore defect tolerance. These features are discussed in relation to the performance of the compound as a semiconductor with efficient charge collection.