Abstract
The silicon wafers for solar cells on which the paste is deposited experience a bowing phenomenon. The thickness of commonly used c-Si wafers is 180 μm or more. When fabricating c-Si solar cells with this wafer thickness, the bowing value is 3 mm or less and the problem does not occur. However, for the thin c-Si solar cells which are being studied recently, the output reduction due to failure during manufacture and cracking are attributed to bowing. In generally, it is known that the bowing phenomenon arises mainly from the paste applied to the back side electrode of c-Si solar cells and the effects of SiNx (silicon nitride) and the paste on the front side are not considered significant. The bowing phenomenon is caused by a difference in the coefficient of expansion between heterogeneous materials, there is the effect of bowing on the front electrode and ARC. In this paper, a partially processed c-Si solar cell was fabricated and a bowing phenomenon variation according to the wafer thicknesses was confirmed. As a result of the experiment, the measured bow value after the firing process suggests that the paste on the front-side indicates a direction different from that of the back-side paste. The bow value increases when Al paste is deposited on SiNx. The fabricated c-Si solar cell was analyzed on basis of the correlation between the bowing phenomenon of the materials and the c-Si wafer using Stoney’s equation, which is capable of analyzing the relationship between bowing and stress. As a result, the bowing phenomenon of the c-Si solar cell estimated through the experiment that the back side electrode is the important element, but also the front electrode and ARC influence the bowing phenomenon when fabricating c-Si solar cells using thin c-Si wafers.
Highlights
Current solar power generation is shifting to thinner crystalline silicon (c-Si) solar cells for cost reduction purposes [1]
Reduction in the production cost is essential for grid parity and thin c-Si solar cells are important elements in this context
Solar cells were fabricated with the Gumi Electronics & Information Technology Research (GERI) and experiments were performed under the same conditions to Institute (GERI) and experiments were performed under the same conditions
Summary
Current solar power generation is shifting to thinner crystalline silicon (c-Si) solar cells for cost reduction purposes [1]. In the PV module, a mismatch of the electrical output occurs due to a decrease in the output of the c-Si solar cell, causing a reduction in the overall electrical output and long-term reliability of the PV module [3,4,5]. Bowing is caused by a difference in the thermal expansion coefficients between the front/rearside electrode and the c-Si wafer [6, 7]. When manufacturing a c-Si solar cell, a Energies 2019, 12, 1593 bowing phenomenon occurs due to this difference in thermal expansion coefficients. To minimize of the occurrence of cracks, it is important to minimize the bowing phenomenon during c-Si solar cell manufacture. The process of thin c-Si cell expansion manufacture, the bowing phenomenon occurs. Coefficients of thermal expansion of the front electrode and the rear electrode are 19.7 × 10 /K and bowing in[7].
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