Coordination Engineering of Cu-Zn-Sn-S Aqueous Precursor for Efficient Kesterite Solar Cells

TL;DR

This paper presents a novel aqueous precursor method using thioglycolic acid to produce stable solutions for efficient Cu-Zn-Sn-S solar cells, achieving over 12% efficiency with environmentally friendly processes.

Contribution

Introduction of thioglycolic acid as a coordination agent to optimize precursor stability and crystallization in CZTSSe solar cell fabrication.

Findings

Achieved CZTSSe solar cell efficiency of 12.2% (certified 12.0%)

Developed ultrastable aqueous precursor with wide storage window

Enhanced environmentally friendly fabrication process

Abstract

Aqueous precursors provide an alluring approach for low-cost and environmentally friendly production of earth-abundant Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. The key is to find an appropriate molecular agent to prepare a stable solution and optimize the coordination structure to facilitate the subsequent crystallization process. Herein, we introduce thioglycolic acid, which possesses strong coordination (-SH) and hydrophilic (-COOH) groups, as the agent and use deprotonation to regulate the coordination competition within the aqueous solution. Ultimately, metal cations are adequately coordinated with thiolate anions, and carboxylate anions are released to become hydrated to form an ultrastable aqueous solution. These factors have contributed to achieving CZTSSe solar cells with efficiency of as high as 12.2% (a certified efficiency of 12.0%) and providing an extremely wide time window for precursor storage and usage. This work represents significant progress in the non-toxic solution fabrication of CZTSSe solar cells and holds great potential for the development of CZTSSe and other metal sulfide solar cells.