Efficiency improvement of passivated emitter and rear cells using annealing process before surface passivation
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Efficiency improvement of passivated emitter and rear cells using annealing process before surface passivation Hanrui Cui1
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, Ning Yang1, Xiao Yuan1, Cui Liu1, Xiaojun Ye1,*, and Hongbo Li1,*
School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
Received: 2 July 2020
ABSTRACT
Accepted: 10 November 2020
Thermal annealing and effective surface passivation are significant to achieve high conversion efficiency (g) of passivated emitter and rear cells (PERC). Thus, we added an annealing process before front and rear surface passivation in the existing production line. We found that the front recombination current (J0,f) and the rear recombination current (J0,r) of annealed PERCs are both lower than baseline PERCs without annealing process, which means better defect repair and passivation effect were achieved. And the average g of annealed PERCs reaches 21.79%, which is 0.23% absolutely higher than that of the baseline PERCs. After that, we further explored the influence of gas composition (0%, 5% and 10% oxygen concentration in nitrogen atmosphere) during annealing process. We found that as the oxygen concentration increases, J0,fs and J0,rs of annealed PERCs (0%, 5%, 10%) are all lower than those of baseline PERCs. Meanwhile, the annealed PERCs (0%, 5%, 10%) get the average g of 21.77%, 21.82% and 21.84% respectively, possessing absolute efficiency increase over the baseline PERCs with the average g of 21.67%. The present work could help enhance the understanding of passivation property and improve the performance of industrial PERC cells.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction It is well known that various impurities can be introduced into the fabrication process of solar cell. Thermal annealing can alleviate the adverse effects of such defects as recombination centers and improve the minority carrier lifetime [1]. Meanwhile, effective surface passivation is significant to achieve high
conversion efficiency (g) of solar cells. In general, thermally grown silicon dioxide (SiO2) is the best surface passivation material for crystalline Si (c-Si), which can significantly saturate the dangling bonds on the silicon surface and reduce the density of interface defects (Dit) [2, 3]. SiO2 layer helps to enhance the passivation quality of the front and rear surfaces for both n- and p-type silicon surfaces [4–7]
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https://doi.org/10.1007/s10854-020-04871-w
J Mater Sci: Mater Electron
and the surface recombination velocity can be less than 10 cm/s on p-type surfaces after annealing [8]. Also, the SiO2 layer can act as a transition layer for passivation film [9]. Studies have shown that when used as a silicon contact layer, silicon dioxide can reduce defects because of its thermal expansion coefficient is one order of magnitude smaller than underlying silicon [10–13]. In recent years, passivated emitter and rear cell (PERC) has bec
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