Abstract
Silicon solar cells are a mainstay of commercialized photovoltaics, and further improving the power conversion efficiency of large-area and flexible cells remains an important research objective1,2. Here we report a combined approach to improving the power conversion efficiency of silicon heterojunction solar cells, while at the same time rendering them flexible. We use low-damage continuous-plasma chemical vapour deposition to prevent epitaxy, self-restoring nanocrystalline sowing and vertical growth to develop doped contacts, and contact-free laser transfer printing to deposit low-shading grid lines. High-performance cells of various thicknesses (55–130 μm) are fabricated, with certified efficiencies of 26.06% (57 μm), 26.19% (74 μm), 26.50% (84 μm), 26.56% (106 μm) and 26.81% (125 μm). The wafer thinning not only lowers the weight and cost, but also facilitates the charge migration and separation. It is found that the 57-μm flexible and thin solar cell shows the highest power-to-weight ratio (1.9 W g−1) and open-circuit voltage (761 mV) compared to the thick ones. All of the solar cells characterized have an area of 274.4 cm2, and the cell components ensure reliability in potential-induced degradation and light-induced degradation ageing tests. This technological progress provides a practical basis for the commercialization of flexible, lightweight, low-cost and highly efficient solar cells, and the ability to bend or roll up crystalline silicon solar cells for travel is anticipated.
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Acknowledgements
This work has been supported by the National Natural Science Foundation of China (numbers 21606171 and 22179054), the China Postdoctoral Science Foundation (numbers 2021M691326, 2015M580205 and 2017T100160), the Natural Science Foundation of Jiangsu Province (number BK20211345) and the Ministry of Science and Technology of the People’s Republic of China (number DL2022014014L). Z.S. acknowledges the support from the Australian Research Council via Discovery Projects (numbers DP200103315, DP200103332 and DP230100685) and Linkage Projects (number LP220200920). Y.L. thanks Baoyu Huang and Zhengfeng Yang for assistance with the experiments; Jiating Wu and Yuxuan Li for assistance with the preparation for publication; and all group members of X.X. and Z.S. for continuous support. Jiangsu University of Science and Technology and LONGi Green Energy Technology Co., Ltd have equal rights of this work.
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Contributions
Y.L. conceived the idea, designed the cells, explored the mechanisms, and wrote and revised the manuscript. X.R. designed the experiments and fabricated the solar cells. M.Y. guided the experimental fabrication technology. Y.Z. was responsible for the flexibility simulation and measurement, figures, tables and preparation for publication. S.Y. and C.H. developed the TCO process. F.P. developed the metallization process and conducted the efficiency certification. M.Q., C.X., J.L. and L.F. managed the project and participated in experiment design. C.S. assisted in characterization and data analysis. D.C., J.X. and C.Y. provided resources and funding support. Z.L. and X.X. organized the research. Z.S. supervised the project.
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Jiangsu University of Science and Technology is in the process of applying for a Chinese invention patent (202311478687.5) related to the subject matter of this manuscript. Z.L. and X.X. are co-founders of LONGi Central R&D Institute. X.R., M.Y., S.Y., C.H., F.P., M.Q., C.X., J.L. and L.F. are employees of LONGi. The other authors declare no competing interests.
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Extended data figures and tables
Extended Data Fig. 1 Cross-sectional HRTEM images.
a, Cross-sectional morphology of the c-Si/i:a-Si:H interface. b, Cross-sectional morphology of c-Si/hydrogen-rich i:a-Si:H/a-Si:H. c, Enlarged cross-sectional morphology of the i:a-SiOx:H (1)/a-Si:H (2) composite gradient passivation layers prepared via continuous-plasma CVD.
Extended Data Fig. 2 Hydrogen content.
Effect of hydrogen content (CH) variation in the epitaxy-preventing composite gradient passivation layers on cell performance. The dashed lines in the panels are fit lines to evaluate the data change trends.
Extended Data Fig. 3 Self-restoring nanocrystalline sowing and vertical growth induction (NSVGI).
a, Cross-sectional HRTEM image of the doped contact layer fabricated via conventional random growth. b, Cross-sectional HRTEM image of the doped contact layer fabricated via self-restoring NSVGI.
Extended Data Fig. 4 Self-restoring nanocrystalline sowing.
a, Relationship between the FF and crystallinity fraction of the n+:nc-SiOx:H window layer with a p+:a-Si:H rear emitter. b, Relationship between the FF and crystallinity fraction of the p+:nc-Si:H rear emitter with the optimal n+:nc-SiOx:H window layer. c,d, Variation of CH in i:a-Si:H (2) with sowing duration via self-restoring nanocrystalline sowing and unrestricted nanocrystalline sowing, respectively. e, Enlarged cross-sectional HRTEM image of i:a-Si:H (2) after the unrestricted nanocrystalline sowing. The dashed lines in the panels (a, b, c, d) are fit lines to evaluate the data change trends.
Extended Data Fig. 5 Contact-free laser transfer printing.
Comparison of the cell performance parameters via conventional screen printing and contact-free laser transfer printing (LTP).
Extended Data Fig. 6 Endurance assessment.
Encapsulation schematics for the SF and FT SHJ modules, as well as the laboratory accreditation certificate for the third-party assessment. The certificate is reproduced with permission from Changzhou Sveck Photovoltaic New Material Co., Ltd.
Extended Data Fig. 7 Durability analysis.
a, Impact of the different TCO layers on the PID resistance of the FT and SF SHJ cells for each thickness. b, Statistical analysis of the anti-PID capacities of the FT and SF cells with the ITO and ICO layers. Temperature: 85 °C, humidity: 85%, bias: −1,500 V, duration: 192 h. c, Statistical analysis of the anti-light-induced degradation capacities of the FT and SF cells with the different passivation and contact layers. d, Light-induced degradation resistance of the FT and SF cells for each thickness. Accumulated illumination of 210 kWh·m−2. The dashed lines in the panels (a, d) are fit lines to evaluate the data change trends.
Extended Data Fig. 8 Power recovery in light-induced degradation.
a, VOC, FF, JSC variation of the FT (57 μm) cell during light-induced degradation ageing. b, VOC, FF, JSC variation of the FT (84 μm) cell during light-induced degradation ageing. c, VOC, FF, JSC variation of the SF (125 μm) cell during light-induced degradation ageing. d, VOC, FF, JSC variation of the conventional SHJ (150 μm) cell during light-induced degradation ageing. The dashed lines in the panels are fit lines to evaluate the data change trends.
Extended Data Fig. 9 Visualization of the surface potential distribution during RF-PECVD.
a, Continuous-plasma CVD process with CRCS (fluctuation < ±0.5%). b, Conventional discontinuous-plasma CVD passivation (fluctuation < ±8%). c, Conventional discontinuous-plasma CVD passivation at the reignition moment.
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Li, Y., Ru, X., Yang, M. et al. Flexible silicon solar cells with high power-to-weight ratios. Nature 626, 105–110 (2024). https://doi.org/10.1038/s41586-023-06948-y
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DOI: https://doi.org/10.1038/s41586-023-06948-y
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