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Hydrogen-enhanced carrier collection enabling wide-bandgap Cd-free Cu2ZnSnS4 solar cells with 11.4% certified efficiency

Nature Energy volume 10, pages 255–265 (2025)Cite this article

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Abstract

Wide-bandgap kesterite Cu2ZnSnS4 offers an economically viable, sustainably sourced and environmentally friendly material for both single-junction and tandem photovoltaic applications. Nevertheless, since 2018 the record efficiency of such solar cells has stagnated at 11%, largely due to carriers recombining before they are collected. Here we demonstrate enhanced carrier collection in devices annealed in a hydrogen-containing atmosphere. We find that hydrogen is incorporated mainly in n-type layers and on the absorber surface. Furthermore, we show that the hydrogen treatment triggers the out-diffusion of oxygen and sodium from the absorber bulk to the surface, favourably diminishing the acceptor concentration at the surface and increasing the p-type doping in the bulk. Consequently, Fermi-level pinning is relieved and carrier transport in the absorber is facilitated. We achieve a certified efficiency of 11.4% in Cd-free devices. Although hydrogenation already plays a major role in silicon photovoltaics, our findings can further advance its application in emerging photovoltaic technologies.

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Fig. 1: Device structure and elemental distribution.
Fig. 2: Elemental redistribution and d-spacing expansion.
Fig. 3: Analysis of the doping profile and carrier transport.
Fig. 4: EBIC and CL analyses.
Fig. 5: Device performance and characterization.

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Data availability

The data that support the findings of this study are available within the Article and its Supplementary Information. Other relevant data are available from the corresponding authors upon reasonable request. Source data are provided with this paper.

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Acknowledgements

We received funding from the Australian Renewable Energy Agency (ARENA) as part of ARENA’s Transformative Research Accelerating Commercialisation (TRAC) Program and the Australian Research Council Discovery Project (DP230102463). X.H. acknowledges financial support of the Australian Research Council Future Fellowship (FT190100756). K.S. acknowledges the Australian Research Council Discovery Early Career Researcher Award (DE230100021) and support from the Australian Centre of Advanced Photovoltaics (ACAP) as a recipient of an ACAP Fellowship (RG172864-B). S.-H.W. acknowledges support from the National Natural Science Foundation of China (grant numbers 11991060 and 12088101). We acknowledge K. Privat for assistance with the CL measurements. We acknowledge the facilities and the scientific and technical assistance of Microscopy Australia at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney and the surface analysis laboratory, SSEAU, MWAC, UNSW. We acknowledge access to NCRIS-funded facilities and expertise at the ion-implantation Laboratory (iiLab), a node of the Heavy Ion Accelerator (HIA) Capability at the Australian National University. We acknowledge the use of the instruments and scientific and technical assistance at the Monash Centre for Electron Microscopy, a Node of Microscopy Australia. We would like to thank D. Vowles and A. Liu for the initial set-up of the EBIC device at Monash Centre for Electron Microscopy. We acknowledge the experimental support provided by the Particles and Catalysis Research Group.

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Authors and Affiliations

  1. Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales, Australia

    Ao Wang, Jialin Cong, Jialiang Huang, Jingwen Cao, Xin Cui, Xiaojie Yuan, Guojun He, Martin A. Green, Kaiwen Sun & Xiaojing Hao

  2. School of Chemical Engineering, University of New South Wales, Sydney, New South Wales, Australia

    Shujie Zhou

  3. Electron Microscope Unit, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia

    Yin Yao

  4. Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria, Australia

    Zhou Xu

  5. Department of Mechanical Engineering, The University of Melbourne, Parkville, Victoria, Australia

    Jefferson Zhe Liu

  6. Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales, Australia

    Julie M. Cairney & Yi-sheng Chen

  7. Eastern Institute of Technology, Ningbo, China

    Su-Huai Wei

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Contributions

X.H., K.S. and M.A.G. supervised the project. A.W. and K.S. proposed the ideas, fabricated and optimized the devices, carried out essential characterization and data analysis, and wrote the manuscript. J.H. collected and analysed the temperature-dependent VOC, TEM, CL and EBIC data. J. Cong conducted the APT measurements and specimen preparation for TEM and CL. J.M.C. and Y.-s.C. contributed to the discussion of the hydrogen detection and APT data analysis. S.Z. assisted in hydrogen treatment and reflectance measurements. J. Cao and J.Z.L. performed the DFT calculations. S.-H.W. contributed to the discussion and analysis. X.C. implemented the ZnSnO layer deposition. Z.X. assisted with the EBIC measurements. Y.Y. and X.Y. assisted with the KPFM measurements. G.H. provided the CIGS solar cells. K.S. conducted the PL and TRPL measurements. J.H., K.S. and X.H. contributed to the overall data analysis and discussion. A.W., K.S. and X.H. were responsible for most of the manuscript revisions. All authors contributed to the manuscript revision.

Corresponding authors

Correspondence to Jialiang Huang, Kaiwen Sun or Xiaojing Hao.

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Competing interests

X.H., A.W. and K.S. declare a pending patent related to hydrogen treatment for chalcogenide solar cells (applicant: NewSouth Innovations Pty Limited, application number: 2024903846). The other authors declare no competing interests.

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Nature Energy thanks Qingbo Meng, Alessandro Romeo, Byungha Shin, Bart Vermang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–19, Notes 1 and 2 and Tables 1 and 2.

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Source data

Source Data Fig. 1

Measured hydrogen concentrations from unprocessed ERDA analysis in both the Ref and HT samples.

Source Data Fig. 4

Raw EBIC line-scan profiles of the Ref and HT devices.

Source Data Fig. 5

Raw data for statistical device performance and temperature-dependent VOC measurements.

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Wang, A., Cong, J., Zhou, S. et al. Hydrogen-enhanced carrier collection enabling wide-bandgap Cd-free Cu2ZnSnS4 solar cells with 11.4% certified efficiency. Nat Energy 10, 255–265 (2025). https://doi.org/10.1038/s41560-024-01694-5

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