A "Redox-free" Synthesis of CZTS Nano Ink

TL;DR

This paper introduces a novel 'redox-free' method for synthesizing CZTS nano ink that achieves superior phase control and purity, addressing key challenges in kesterite solar cell fabrication.

Contribution

It presents a new non-toxic, redox-free synthesis process for CZTS nano ink that effectively prevents secondary phase formation and improves phase purity.

Findings

Nanoparticle inks show better phase control than molecular solutions.

The synthesis method prevents secondary phase formation.

Nanoparticles follow a more ideal phase formation path.

Abstract

A large open-circuit (V$_{oc}$) deficit restricts current kesterite device performance. The primary challenge is to achieve control over the phase composition and purity of the kesterite absorber. This is hampered by the fact that the metals copper and tin have multiple valence states and this leads inevitably to the formation of multiple phases. Specifically for solution-based fabrication procedures for kesterite, the pursuit of phase purity extends to the synthesis of CZTS precursor solution or nanoparticle dispersed inks (nano inks). In this work, a "redox-free" synthesis of CZTS nano ink is developed by mixing metal precursors with careful valence state control in non-toxic solvents. The issue of secondary phase formation during the synthesis process of kesterite is effectively resolved. Additionally, molecular solutions and nanoparticle inks with identical compositions exhibit significantly different abilities in phase control. Nanoparticles pre-synthesized in the solution state exhibit superior phase control by following a more ideal phase formation path. This provides a new pathway for the synthesis of kesterite with unprecedented control of the phase composition and purity.