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Design rules for high-efficiency both-sides-contacted silicon solar cells with balanced charge carrier transport and recombination losses


The photovoltaic industry is dominated by crystalline silicon solar cells. Although interdigitated back-contact cells have yielded the highest efficiency, both-sides-contacted cells are the preferred choice in industrial production due to their lower complexity. Here we show that omitting the layers at the front side that provide lateral charge carrier transport is the key to excellent optoelectrical properties for both-sides-contacted cells. This results in a conversion efficiency of 26.0%. In contrast to standard industrial cells with a front side p–n junction, this cell exhibits the p–n junction at the back surface in the form of a full-area polycrystalline silicon-based passivating contact. A detailed power-loss analysis reveals that this cell balances electron and hole transport losses as well as transport and recombination losses in general. A systematic simulation study led to some fundamental design rules for future >26% efficiency silicon solar cells and demonstrates the potential and the superiority of these back-junction solar cells.

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Fig. 1: Overview of notable silicon solar cells.
Fig. 2: Schematic cross-section of different silicon solar cell designs.
Fig. 3: 1-sun IV parameters (in-house measurements) of all the fabricated solar cells.
Fig. 4: PLA of the best-performing solar cells.
Fig. 5: Influence of front surface conductivity on the device performance.
Fig. 6: Simulated electrical PLA together with the power output of different FJ and BJ cells as a function of the c-Si bulk resistivity ρb.

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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We thank S. Seitz, A. Leimenstoll, F. Schätzle, N. Brändlin, A. Seiler, D. Leclerc and H. Steidl for their contributions during the solar cell processing and E. Schäffer and F. Martin for performing measurements. This work was partially supported by the German Federal Ministry for Economic Affairs and Energy under contract no. 03EE1031A (PaSoDoble).

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A.R., R.M., C.R., J.B., M.B. and M.H. conceived the idea. A.R. and J.B. designed the experiment. A.R. coordinated the fabrication of the solar cells, optimized the Al2O3 surface passivation and carried out the data evaluation and simulation study. C.R. and R.M. contributed to the process developments required for the solar cell fabrication. F.F., B.S. and M.H. developed the TOPCon stack. A.F. contributed to the device simulations and interpretation. M.H. and S.W.G. contributed to the definition and presentation of the article contents and organized the research. A.R. wrote the paper, and all the co-authors participated in the discussions and reviewed the manuscript.

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Correspondence to Armin Richter.

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Richter, A., Müller, R., Benick, J. et al. Design rules for high-efficiency both-sides-contacted silicon solar cells with balanced charge carrier transport and recombination losses. Nat Energy 6, 429–438 (2021).

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