Planar p–n homojunction perovskite solar cells with efficiency exceeding 21.3%

Abstract

Perovskite solar cells (PSCs) have emerged as an attractive photovoltaic technology thanks to their outstanding power conversion efficiency (PCE). Further improvement in the device efficiency is limited by the recombination of the charge carriers in the perovskite layer even when employing heterojunction-based architectures. Here, we propose and demonstrate a p-type perovskite/n-type perovskite homojunction whose built-in electric field promotes oriented transport of the photo-induced carriers, thus reducing carrier recombination losses. By controlling the stoichiometry of the perovskite precursors, we are able to induce n-type or p-type doping. We integrate the homojunction structure in a planar PSC combining a thermally evaporated p-type perovskite layer on a solution-processed n-type perovskite layer. The PSC with a MAPbI3 homojunction achieves a PCE of 20.80% (20.5% certified PCE), whereas the PSC based on a FA0.15MA0.85PbI3 homojunction delivers a PCE of 21.38%. We demonstrate that the homojunction structure is an effective approach, beyond existing planar heterojunction PSCs, to achieve highly efficient PSCs with reduced carrier recombination losses.

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Fig. 1: Structure of planar PSCs with and without the homojunction and fabrication schematic of the homojunction PSC fabricated by the combined deposition method.
Fig. 2: Carrier generation and recombination of the planar PSCs with and without the homojunction.
Fig. 3: Doping, carrier transport and optical properties of the doped perovskite films.
Fig. 4: Cross-sectional KPFM measurement for the perovskite homojunction device under different bias voltages.
Fig. 5: Photovoltaic performance of the planar PSCs with and without the homojunction.
Fig. 6: The perovskite film analysis and stability assessment of the standard p–i–n PSC and the homojunction PSC.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work is supported partially by the National Natural Science Foundation of China (grant no. 51772096), the Natural Science Foundation of Beijing Municipality (L172036), Joint Funds of the Equipment Pre-Research and Ministry of Education (6141A020225), the Par-Eu Scholars Program, the Science and Technology Beijing 100 Leading Talent Training Project, the Beijing Municipal Science and Technology Project (Z161100002616039), the Fundamental Research Funds for the Central Universities (2016JQ01 and 2017ZZD02) and the NCEPU `Double First-Class' Graduate Talent Cultivation Program. We thank Z. Cheng, R. Xu and Z. Liu for KPFM measurements and analysis, and X. Han and Z. Li for high-resolution TEM measurements. P.C. acknowledges the scholarship from the China Scholarship Council and thanks G. Cao for fruitful discussions.

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M.L. supervised the project. P.C. and M.L. conceived and designed the experiments. P.C. and D.W. performed the main experiments and characterization, and wrote the manuscript. J.J. helped with device optimization and fabrication. H.H. helped with KPFM measurements. E.J. performed Hall measurements and analysed the data. T.W. performed the simulation with wxAMPs. P.C., D.W., J.J., H.H., E.J., S.D., T.W., W.W. and M.L. contributed to the data analysis, discussed the results and commented on the manuscript.

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Correspondence to Meicheng Li.

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Supplementary Notes 1–3, Supplementary Figures 1–21, Supplementary Tables 1–6, Supplementary References.

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Cui, P., Wei, D., Ji, J. et al. Planar p–n homojunction perovskite solar cells with efficiency exceeding 21.3%. Nat Energy 4, 150–159 (2019). https://doi.org/10.1038/s41560-018-0324-8

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