Influence of using amorphous silicon stack as front heterojunction structure on performance of interdigitated back contact-heterojunction solar cell (IBC-HJ)

Abstract

Interdigitated back contact-heterojunction (IBC-HJ) solar cells can have a conversion efficiency of over 25%. However, the front surface passivation and structure have a great influence on the properties of the IBC-HJ solar cell. In this paper, detailed numerical simulations have been performed to investigate the potential of front surface field (FSF) offered by stack of n-type doped and intrinsic amorphous silicon (a-Si) layers on the front surface of IBC-HJ solar cells. Simulations results clearly indicate that the electric field of FSF should be strong enough to repel minority carries and cumulate major carriers near the front surface. However, the over-strong electric field tends to drive electrons into a-Si layer, leading to severe recombination loss. The n-type doped amorphous silicon (n-a-Si) layer has been optimized in terms of doping level and thickness. The optimized intrinsic amorphous silicon (i-a-Si) layer should be as thin as possible with an energy band gap (E_g) larger than 1.4 eV. In addition, the simulations concerning interface defects strongly suggest that FSF is essential when the front surface is not passivated perfectly. Without FSF, the IBC-HJ solar cells may become more sensitive to interface defect density.

Keywords

amorphous silicon / front surface field / simulations / interdigitated back contact-heterojunction solar cells

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Acknowledgements

This work is supported by the National Natural Science Foundation of China (Grant Nos. 11104319, 11274346, 51202285, 61234005, 51172268 and 51402347), the Solar Energy Action Plan of the Chinese Academy of Sciences (Grant Nos. Y1YT064001, Y1YF034001 and Y2YF014001), and Sci. & Tech. Commission Project of Beijing Municipality (Grant No. Z151100003515003).

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