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Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%


Improving the photoconversion efficiency of silicon solar cells is crucial to further the deployment of renewable electricity. Essential device properties such as lifetime, series resistance and optical properties must be improved simultaneously to reduce recombination, resistive and optical losses. Here, we use industrially compatible processes to fabricate large-area silicon solar cells combining interdigitated back contacts and an amorphous silicon/crystalline silicon heterojunction. The photoconversion efficiency is over 26% with a 180.4 cm2 designated area, which is an improvement of 2.7% relative to the previous record efficiency of 25.6%. The cell was analysed to characterize lifetime, quantum efficiency, and series resistance, which are essential elements for conversion efficiency. Finally, a loss analysis pinpoints a path to approach the theoretical conversion efficiency limit of Si solar cells, 29.1%.

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Figure 1: Schematic image and IV curve of the HJ-IBC cell.
Figure 2: Schematic images of typical c-Si solar cells and record efficiencies.
Figure 3: Quantum efficiency and reflection spectra.
Figure 4: Extraction of series resistance and ideality factor using Suns-V OC.
Figure 5: Effective lifetime and implied IV of the practical efficiency limit.
Figure 6: Summary of loss elements.


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This work was supported in part by the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry of Japan.

Author information




K.Yoshikawa designed the experiments and analysed the data. D.A. and K.Yamamoto supervised the study. K.Yoshikawa., H.K., W.Y., T.I., K.K., K.N., T.U. and M.K. contributed to development of the HJ-IBC cell, optimization of optical properties, passivation quality and resistivity. K.Yoshikawa, D.A. and K.Yamamoto wrote the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Kunta Yoshikawa.

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The authors are employees of Kaneka Corporation.

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Yoshikawa, K., Kawasaki, H., Yoshida, W. et al. Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%. Nat Energy 2, 17032 (2017).

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