Abstract
Perovskite solar cells (PSCs) are promising low-cost photovoltaic technologies with high solar-to-electric power conversion efficiency (PCE). The heterojunction structure between perovskite and charge extraction layers is crucial to the photovoltaic performance of PSCs. Here, we report efficient inverted-structured PSCs with a perovskite–fullerene graded heterojunction (GHJ), in which the electron-accepting material is distributed in the perovskite layer with a gradient. This structure can enhance the PCE as it improves the photoelectron collection and reduces recombination loss, especially for the formamidinium cation-based perovskite. The conformal fullerene coating on perovskite during the GHJ deposition achieves a full coverage with reduced layer thickness, thus minimizing the resistive loss in larger sized devices. Our strategy enables the fabrication of centimetre-scale PSCs showing high efficiency with small hysteresis and good stability. A PCE of 18.21% was certified by an independent institution for cells with an aperture area of 1.022 cm2.
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Acknowledgements
This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), the Advanced Low Carbon Technology Research and Development Program (ALCA) of JST, and the National Natural Science Foundation of China (grant no. 11574199). L.H. thanks M. Grätzel of the Swiss Federal Institute of Technology, H. Naito of Osaka Prefecture University, and M. Hiramoto of the Institute for Molecular Science for their useful discussions. Y.W. and L.H. thank N. Ishida and ‘Quantum Beam Unit of Advanced Key Technologies Division in National Institute for Materials Science’ for the SIMS measurement. X.Y. thanks X. Kong of Shanghai Jiao Tong University for the TRPL experiments.
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L.H. supervised the project. Y.W. and L.H. conceived and designed the experiments. Y.W., X.Y. and W.C. performed the main experiments, and characterization. Y.W. wrote the manuscript. All authors contributed to the data analysis, discussed the results and commented on the manuscript.
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Wu, Y., Yang, X., Chen, W. et al. Perovskite solar cells with 18.21% efficiency and area over 1 cm2 fabricated by heterojunction engineering. Nat Energy 1, 16148 (2016). https://doi.org/10.1038/nenergy.2016.148
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DOI: https://doi.org/10.1038/nenergy.2016.148
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