In situ recombination junction between p-Si and TiO_2 enables high-efficiency monolithic perovskite/Si tandem cells

Creators: Shen, Heping; Omelchenko, Stefan T.; Jacobs, Daniel A.; Yalamanchili, Sisir; Wan, Yimao; Yan, Di; Phang, Pheng; Duong, The; Wu, Yiliang; Yin, Yanting; Samundsett, Christian; Peng, Jun; Wu, Nandi; White, Thomas P.; Andersson, Gunther G.; Lewis, Nathan S.; Catchpole, Kylie R.

Abstract

Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Here, we describe a two-terminal perovskite/Si tandem design that increases the Si cell's output in the simplest possible manner: by placing a perovskite cell directly on top of the Si bottom cell. The advantageous omission of a conventional interlayer eliminates both optical losses and processing steps and is enabled by the low contact resistivity attainable between n-type TiO_2 and Si, established here using atomic layer deposition. We fabricated proof-of-concept perovskite/Si tandems on both homojunction and passivating contact heterojunction Si cells to demonstrate the broad applicability of the interlayer-free concept. Stabilized efficiencies of 22.9 and 24.1% were obtained for the homojunction and passivating contact heterojunction tandems, respectively, which could be readily improved by reducing optical losses elsewhere in the device. This work highlights the potential of emerging perovskite photovoltaics to enable low-cost, high-efficiency tandem devices through straightforward integration with commercially relevant Si solar cells.

Additional Information

© 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 1 August 2018; Accepted 15 November 2018; Published 14 December 2018. We would like to thank S. Surve for the mask fabrication and D. Sheng for the STEM results discussion. We greatly appreciate T. Lu and Y. Liu for help with the AFM measurement, D. Walter and T. Kho for discussion about the passivation of Si solar cells, P. Zhang, Y. Zhang, and L. Wang for coordination of the EQE measurement, W. Liang for optimization of the texturing process, and H. T. Nguyen for optical analysis. The electron spectroscopy apparatus was built with a grant from the Australian Research Council (LE0989068). We acknowledge the equipment and support provided by the Australian Microscopy and Microanalysis Research Facility (AMMRF) and the Australian National Fabrication Facility (ANFF) at the South Australian nodes of the AMMRF and ANFF under the National Collaborative Research Infrastructure Strategy. This work was supported by the Australian Government through the Australian Renewable Energy Agency (ARENA), grant MG005, and the Australian Research Council through grant FT13010916. Responsibility for the views, information, or advice expressed herein is not accepted by the Australian Government. Part of the experiment was performed at ANFF ACT Node at the Australian National University. The conception and experimental realization of the TiO_2 deposition and ohmic contact behavior in the tandem solid-state device structure are based on work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under award no. DE-SC0004993. Author contributions: N.S.L. and K.R.C. supervised the research and coordinated the collaboration. N.S.L., S.T.O., and S.Y. were instrumental in generating the concept for this work. H.S. designed experiments as well as fabricated and characterized devices. D.A.J. helped with data analysis, provided the physical theory, and performed simulations. S.T.O., S.Y., N.W., and Y. Wa. contributed to preparing different TiO2 materials and the design of experiments to characterize the TiO_2/Si contacts. Y. Wa., Y. Wu, T.D., and T.P.W. supplied expertise in tandem design. P.P., C.S., Y. Wu, and D.Y. helped with Si solar cell design and fabrication. T.D. and J.P. assisted in perovskite device fabrication and device stability analysis. Y.Y. and G.G.A. were responsible for the energy level characterization of the ALD-TiO2 layer. H.S. and D.A.J. prepared the manuscript, and N.S.L, K.R.C., S.T.O., and S.Y. helped with its editing. All authors reviewed and contributed to the final manuscript. Competing interests: S.T.O., S.Y., and N.S.L. are inventors on a provisional U.S. patent application related to this work filed by the California Institute of Technology (no. 62/662,852, filed 26 April 2018). The authors declare that there are no other competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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