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Surface Microstructural Reconstruction of CdS Buffers Enables Low-Voltage-Loss Kesterite Solar Cells With >15%
Jingchen Wang1,2, Shudan Chen1,2, Xiao Xu1
1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, P. R. China.
Advanced Materials (Deerfield Beach, Fla.)
|May 23, 2026
Summary
Chemical polishing of cadmium sulfide (CdS) buffer layers in kesterite solar cells improves microstructure and crystallinity. This surface reconstruction strategy enhances solar cell efficiency and reduces voltage loss, advancing photovoltaic technology.
Area of Science:
- Materials Science
- Renewable Energy
- Photovoltaics
Background:
- Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cell performance depends heavily on the CZTSSe/CdS heterojunction quality.
- Chemical bath deposition (CBD) of CdS buffer layers faces challenges due to competing nucleation processes, affecting morphology, crystallinity, and defects.
- Conventional CBD process regulation has limitations in optimizing CdS buffer layers for high-performance solar cells.
Purpose of the Study:
- To develop a surface microstructural reconstruction strategy for CdS buffer layers in CZTSSe solar cells.
- To overcome the limitations of conventional CBD by improving CdS film quality.
- To enhance the performance of kesterite solar cells through optimized buffer layers.
Main Methods:
- A chemical polishing technique using a Na2S/thiourea aqueous solution was applied to CZTSSe/CdS films.
- The polishing process selectively removed low-quality CdS particulates.
- Surface recrystallization and sulfur-vacancy compensation were induced in the CdS films.
Main Results:
- Polished CdS films exhibited improved microstructure, enhanced crystallinity, and more homogeneous surface electrical properties.
- Kesterite solar cells achieved a champion efficiency of 15.3% with a high open-circuit voltage (VOC) of 560 mV.
- A record-low open-circuit voltage deficit (Eg/e-VOC) of < 0.5 V was achieved, indicating reduced voltage loss.
Conclusions:
- Chemical polishing is an effective strategy for reconstructing CdS buffer layers, significantly improving kesterite solar cell performance.
- The method suppresses interfacial charge recombination and accelerates charge transport, leading to higher efficiency and lower voltage loss.
- This post-deposition approach offers a broadly applicable paradigm for enhancing CBD-CdS-based optoelectronic devices.
