Small Molecule Thiol Self-Assembled Interlayer Enhances Carrier Extraction at CZTSSe/CdS Interface for High Efficiency Photovoltaics.

Authors

Yawei Wang, Xingyu Lu, Sur Lig, Lingling Wang, Hancheng Zhu, Guorui Wang, Yinglin Wang, Changhua Wang, Xintong Zhang, Yichun Liu

Published in

ACS applied materials & interfaces. Sep 16, 2026. Epub Sep 16, 2026.

Abstract

Efficient carrier extraction at the CZTSSe/CdS heterojunction is essential for high-performance CZTSSe solar cells. However, the uneven distribution of nucleation sites on polycrystalline CZTSSe often leads to nonuniform CdS nucleation and growth, resulting in defect-rich heterojunctions and enhanced interfacial recombination. Herein, we report a small molecule thiol self-assembled interlayer (thiol-SAI) strategy to regulate CdS nucleation and growth on CZTSSe through the directional interaction between thiol-containing molecules and the absorber surface. By comparing thiol molecules bearing hydroxyl, carboxyl, amino, and sulfonic acid terminal groups, sodium 2-mercaptoethanesulfonate (Mesna) is identified as the most effective interfacial modifier. The thiol group (-SH) anchors onto the CZTSSe surface to form a Mesna SAI with outward-oriented sulfonic acid functionalities. This interlayer significantly improves surface wettability and promotes uniform heterogeneous nucleation, enabling the growth of a compact, highly crystalline, and low-defect CdS buffer layer with enhanced grain-boundary coverage. Consequently, interfacial recombination is suppressed, and the heterojunction recombination activation energy increases from 59.27 to 69.50 meV. As a result, the power conversion efficiency is improved from 11.50% to 12.93%. This work demonstrates that thiol-SAI-assisted interface engineering provides an effective strategy for coordinating buffer-layer growth with heterojunction quality, offering a general molecular-level approach for optimizing charge extraction in solution-processed thin-film solar cells.

PMID:
42748008
Bibliographic data and abstract were imported from PubMed on 17 Sep 2026.

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