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Highly efficient Cu2ZnSn(S,Se)4 bifacial solar cell via a composition gradient strategy through the molecular ink

基于成分梯度策略制备高效率铜锌锡硫硒双面电池

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Abstract

The use of transparent conducting oxide (TCO) as a substrate in Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells allows for advanced applications, such as bifacial, semi-transparent, and tandem solar cells with the capability to increase power density generation. However, the efficiency of this kind of solar cell is still below 6% based on the low-cost solution process. In this work, we develop a composition gradient strategy and demonstrate a 6.82% efficient CZTSSe solar cell on F:SnO2 (FTO) substrate under the ambient condition. The composition gradient is realized by simply depositing the precursor inks with different Zn/Sn ratios. To verify that the high performance of the solar cell is attributed to the composition gradient strategy rather than the sole change of the Zn/Sn ratio, devices based on absorbers with varied Zn/Sn ratios are fabricated. Furthermore, the structure and surface morphology of the CZTSSe films with/without composition gradients are examined. The presence of elemental gradient through the depth of the CZTSSe films before and after annealing is confirmed by secondary ion mass spectroscopy analysis. It is found that the composition gradient enhances the crystallinity of the absorber, reduces the surface roughness as well as device parasitic losses, contributing to a higher fill factor, open-circuit voltage and conversion efficiency.

摘要

使用透明导电氧化物玻璃作为铜锌锡硫硒(CZTSSe)薄膜太阳电池的衬底可拓展其应用范围, 如双面电池、半透明电池或者叠层电池.目前, 基于溶液法制备的该类太阳电池的光电转换效率仍低于6%. 本文中, 我们开发了一种成分梯度策略, 并在空气环境中于掺氟二氧化锡衬底上制备出了光电转换效率为6.82%的CZTSSe薄膜太阳电池. 成分梯度主要是通过沉积具有不同Zn/Sn比的分子前驱体溶液来实现的. 为了证明电池性能的提高归因于成分梯度, 而非单纯改变Zn/Sn比, 本工作制备并比较了基于不同Zn/Sn比吸收层的器件性能. 此外, 本工作对有/无成分梯度的CZTSSe薄膜的结构和表面形貌进行了研究, 并通过二次离子质谱分析证实了退火前后CZTSSe薄膜成分的深度梯度分布. 研究发现, 成分梯度策略改善了吸收层的结晶性, 降低了吸收层的表面粗糙度及器件的寄生损耗, 从而提高了填充因子、开路电压和转换效率.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (62074168), and the Fundamental Research Foundations for the Central Universities (20lgpy04). We also thank Prof. Hui Shen, Prof. Wan Yue, Prof. Zhengke Li and Prof. Zhuang Xie for the facility support.

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Authors and Affiliations

  1. Guangzhou Key Laboratory of Flexible Electronic Materials and Wearable Devices, State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-Sen University, Guangzhou, 510275, China

    Saqib Nawaz Khan, Sijie Ge  (葛思洁), Yuxiang Huang  (黄宇翔), Han Xu  (徐菡), Wentao Yang  (杨文韬), Ening Gu  (顾鄂宁), Xianzhong Lin  (林显忠) & Guowei Yang  (杨国伟)

  2. Key Laboratory of Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-Sen University, Guangzhou, 510275, China

    Saqib Nawaz Khan, Sijie Ge  (葛思洁), Yuxiang Huang  (黄宇翔), Han Xu  (徐菡), Wentao Yang  (杨文韬), Ening Gu  (顾鄂宁) & Xianzhong Lin  (林显忠)

  3. School of Physics, Sun Yat-Sen University, Guangzhou, 510275, China

    Ruijiang Hong  (洪瑞江)

  4. Institute of New Energy Technology, College of Information and Technology, Jinan University, Guangzhou, 510632, China

    Yaohua Mai  (麦耀华)

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  1. Saqib Nawaz Khan
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  2. Sijie Ge  (葛思洁)
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Contributions

Lin X conceived and supervised the project; Khan SN conducted most of the experiments and wrote the draft of the manuscript; Ge S and Huang Y prepared some of the samples. Xu H supported the annealing of samples. Yang W performed X-ray diffraction measurements; Hong R, Mai Y and Yang G participated in the discussion and analysis of the data. Khan SN, Gu E and Lin X wrote the manuscript with discussion and input from all the authors.

Corresponding authors

Correspondence to Ening Gu  (顾鄂宁) or Xianzhong Lin  (林显忠).

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Conflict of interest

The authors declare that they have no conflict of interest.

Saqib Nawaz Khan received his Master’s degree in materials physics and chemistry from Sun Yat-Sen University in 2021. Currently he is pursuing his doctoral degree at the Institute of Physics, Chinese Academy of Sciences. His research interest includes the synthesis and characterization of energy materials and their applications in optoelectronic devices. His current research focus is on kesterite Cu2ZnSn(S,Se)4 and perovskite thin-film solar cells.

Ening Gu received her PhD degree in materials science from Friedrich-Alexander-Universität Erlangen-Nürnberg in 2019 under the supervison of Prof. Christoph J. Brabec. Currently, she works as a postdoctoral fellow at the School of Materials Science and Engineering, Sun Yat-Sen University. Her research interests focus on emerging photovoltaic materials, solution-processed optoelectronic semiconductors and devices.

Xianzhong Lin received his PhD degree from Technische Universität Berlin, Germany, in 2014. Before joining Sun Yat-Sen University as an associate professor in 2017, he worked as a postdoctoral researcher at Helmholtz-Zentrum Berlin für Materialien und Energie and Friedrich-Alexander-Universität Erlangen-Nürnberg for three years. His research focuses on highly efficient and stable thin-film solar cells based on printing approach.

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Khan, S.N., Ge, S., Huang, Y. et al. Highly efficient Cu2ZnSn(S,Se)4 bifacial solar cell via a composition gradient strategy through the molecular ink. Sci. China Mater. 65, 612–619 (2022). https://doi.org/10.1007/s40843-021-1769-7

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