A precisely regulating phase evolution strategy for highly efficient kesterite solar cells

TL;DR

This paper introduces a precise pressure control strategy during selenization that optimizes phase evolution in kesterite CZTSSe solar cells, resulting in record efficiency and improved crystalline quality.

Contribution

It presents a novel kinetic regulation method via chamber pressure control to enhance phase evolution and efficiency in CZTSSe solar cells.

Findings

Achieved 14.1% efficiency in CZTSSe solar cells.

Suppressed secondary phases by controlling Se vapor during synthesis.

Provided new insights into selenization mechanisms for better device performance.

Abstract

Phase evolution during the selenization is crucial for high-quality kesterite Cu2ZnSn(S, Se)4 (CZTSSe) absorbers and efficient solar cells. Herein, we regulate kinetic process of phase evolution from Cu+-Sn4+-MOE (MOE: 2-methoxyethanol) system by precisely controlling positive chamber pressure. We found that, at the heating-up stage, Se vapor concentration is intentionally suppressed in low-temperature region, which effectively reduces collision probability between the CZTS and Se atoms, thus remarkably inhibiting formation of secondary phases on the surface and multiple-step phase evolution processes. This strategy enables the phase evolution to start at relatively higher temperature and thereby leading to high crystalline quality CZTSSe absorber with fewer defects, and corresponding CZTSSe solar cell can present 14.1% efficiency (total area), which is the highest result so far. This work provides important insights into selenization mechanism of CZTSSe absorbers and explores a new way of kinetic regulation strategy to simplify the phase evolution path to efficient CZTSSe solar cells.