Multinary Alloying Suppresses Defect Formation in Emerging Inorganic Solar Cells

TL;DR

This paper demonstrates that multinary alloying in CZTSSe solar cells reduces defect formation and charge losses, leading to improved efficiency and offering new pathways for defect control in inorganic photovoltaics.

Contribution

It introduces an elemental synergistic alloying approach to mitigate deep defects in CZTSSe, enhancing charge collection and cell efficiency.

Findings

Deep defect in CZTSSe exhibits donor characteristics.

Alloying weakens metal-chalcogen bonds and intermediate phase stability.

Achieved solar cell efficiency over 14.5%.

Abstract

The Cu2ZnSn(S, Se)4 (CZTSSe) emerging inorganic solar cell is highly promising for accelerating the large-scale and low-cost applications of thin-film photovoltaics. It possesses distinct advantages such as abundant and non-toxic constituent elements, high material stability, and excellent compatibility with industrial processes. However, CZTSSe solar cells still face challenges related to complex defects and charge losses. To overcome these limitations and improve the efficiency of CZTSSe solar cells, it is crucial to experimentally identify and mitigate deep defects. In this study, we reveal that the dominant deep defect in CZTSSe materials exhibits donor characteristics. We propose that incomplete cation exchange during the multi-step crystallization reactions of CZTSSe is the kinetics mechanism responsible for the defect formation. To address this issue, we introduce an elemental synergistic alloying approach aimed at weakening the metal-chalcogen bond strength and the stability of intermediate phases. This alloying strategy has facilitated the kinetics of cation exchange, leading to a significant reduction in charge losses within the CZTSSe absorber. As a result, we have achieved a cell efficiency of over 14.5%. These results represent a significant advancement for emerging inorganic solar cells and additionally bring more opportunities for the precise identification and regulation of defects in a wider range of multinary inorganic compounds.