Intrinsic defects in photovoltaic perovskite variant Cs2SnI6

TL;DR

This study investigates intrinsic defects in the photovoltaic material Cs2SnI6 using first-principles calculations, revealing dominant iodine vacancies and tin interstitials responsible for n-type conduction, with implications for synthesis conditions.

Contribution

It provides the first detailed analysis of intrinsic defects in Cs2SnI6, highlighting defect types, formation energies, and strategies to control defect formation for improved photovoltaic performance.

Findings

Iodine vacancy and tin interstitial are the dominant defects.

Deep defect levels are present in the band gap.

I-rich conditions can suppress deep defect formation.

Abstract

Note: This paper has been published in Physical Chemistry Chemical Physics, which can be viewed at the following URL: http://doi.org/10.1039/C5CP03102H Cs2SnI6, a rarely studied perovskite variant material, is recently gaining a lot of interest in the field of photovoltaics owing to its nontoxity, air-stability and promissing photovoltaic properties. In this work, we report intrinsic defects in Cs2SnI6 using first-principles density functional theory calculations. It is revealed that iodine vacancy and tin interstitial are the dominant defects that are responsible for the intrinsic n-type conduction in Cs2SnI6. Tin vacancy has a very high formation energy (>3.6 eV) due to the strong covalency in the Sn-I bonds and is hardly generated for p-type doping. All the dominant defects in Cs2SnI6 have deep transition levels in the band gap. It is suggested that the formation of the deep defects can be suppressed significantly by employing an I-rich synthesis condition, which is inevitable for photovoltaic and other semiconductor applications.