A critical review on rational composition engineering in kesterite photovoltaic devices: self-regulation and mutual synergy

Abstract

Composition engineering has been one of the most crucial strategies to match well with both bulk and heterojunction interfaces of absorbers in kesterite-based Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells. The important advancements and breakthroughs of photovoltaic performance are achieved by the self-regulation and mutual synergy effects of the multielement compositions and processing conditions of CZTSSe films. However, these aspects also suggest that the intrinsic defects and interface contact properties are more complicated, and they are sensitive to the composition. Here, this review focuses on composition engineering to regulate the physicochemical and optoelectronic properties of CZTSSe and correlates absorbers' bulk and heterojunction interfaces with device performance. It is important to further consider the mutual synergy beyond self-regulation to discover new roles of existing composition or activate new roles by other approaches. Such efforts based on the background of CZTSSe composition urgently need to integrate the atomistic level and charge carrier dynamic process characterization with numerical simulations in future studies.