Cadmium-Free Buffer Layer Materials for Kesterite Thin-Film Solar Cells: An Overview

Nafees Ahmad () and Guangbao Wu ()
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Nafees Ahmad: College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
Guangbao Wu: School of Materials Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

Energies, 2025, vol. 18, issue 12, 1-18

Abstract: Kesterite (CZTS/CZTSSe) thin-film solar cells are considered an eco-friendly, earth-abundant, and low-cost photovoltaic technology that can fulfill our future energy needs. Due to its outstanding properties including tunable bandgap and high absorption coefficient, the power conversion efficiency (PCE) has reached over 14%. However, toxic cadmium sulfide (CdS) is commonly used as an n-type buffer layer in kesterite thin-film solar cells (KTFSCs) to form a better p–n junction with the p-type CZTS/CZTSSe absorber. In addition to its toxicity, the CdS buffer layer shows parasitic absorption at low wavelengths (400–500 nm) owing to its low bandgap (2.4 eV). For the last few years, several efforts have been made to substitute CdS with an eco-friendly, Cd-free, cost-effective buffer layer with alternative large-bandgap materials such as ZnSnO, Zn (O, S), In 2 Se 3 , ZnS, ZnMgO, and TiO 2 , which showed significant advances. Herein, we summarize the key findings of the research community using a Cd-free buffer layer in KTFSCs to provide a current scenario for future work motivating researchers to design new materials and strategies to achieve higher performance.

Keywords: kesterite solar cells; Cd-free buffer layer; interface engineering; efficiency; environmentally friendly materials (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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