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Ohimc Contact Formation Mechanism of Silver–Aluminum Paste Metallization on the p+ Emitter of n-Type Crystalline Silicon Solar Cells

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Abstract

The development of high-efficiency n-type crystalline silicon (c-Si) solar cells primarily depends on the application of silver–aluminum (Ag–Al) paste metallization. To deeply reveal and clarify the formation mechanism of the ohmic contact between Ag–Al paste and the p+-Si emitter, the microstructure of the Ag/Si contact interface and the migration of Al to the interface during sintering were investigated. The results showed that the sintered Ag/Si interface contained a glass phase layer with a thickness less than 500 nm, in which a large number of Ag colloids were embedded. This is the same as the Ag/Si contact interface formed by Ag paste metallization on p-type c-Si cells. Compared with Ag paste, Ag–Al paste provides a considerably lower contact resistance with the p+ emitter. Electrical tests revealed a smaller Ag/Si contact resistance and higher Ag electrode resistance with increasing Al concentrations in the Ag–Al paste. In the study of the action mechanism of Al, scanning electron microscopy images illustrated that during sintering, Al powder dissolves in the glass melt at ~ 600°C and reaches the contact interface with the flowing glass melt. As the temperature exceeded 700°C, the mutual diffusion of Al-Si across the Ag/Si contact interface enables Al to enter the Si substrate. The electrochemical capacitance–voltage test results confirmed that the p-type doping concentration of Al in the Si surface significantly increased, leading to a reduction in the shunt resistance. Consequently, the formation of Ag/Si ohmic contact with significantly low contact resistance was completed.

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Acknowledgments

This work is supported by the Fundamental Research Funds for the Central Universities.

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Authors and Affiliations

  1. Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai, 200237, China

    Xinjie Sun, Yunxia Yang, Xiao Yuan, Hongbo Li & Hua Tong

  2. School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China

    Juanjuan Xing

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  1. Xinjie Sun
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  2. Juanjuan Xing
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  3. Yunxia Yang
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  4. Xiao Yuan
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  5. Hongbo Li
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Correspondence to Juanjuan Xing or Hua Tong.

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Sun, X., Xing, J., Yang, Y. et al. Ohimc Contact Formation Mechanism of Silver–Aluminum Paste Metallization on the p+ Emitter of n-Type Crystalline Silicon Solar Cells. J. Electron. Mater. 51, 5717–5722 (2022). https://doi.org/10.1007/s11664-022-09821-2

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