Investigation of the controlling parameters on the bowing phenomenon in ultra-thin crystalline silicon solar cells

Abstract

A reduction in silicon material consumption in the photovoltaic industry is required for cost reduction. Development of ultra-thin crystalline silicon (c-Si) solar cell (<120 μm) is a promising way to significantly cut down the production cost of the cell modules. However, the ultra-thin c-Si solar cells suffer from the bowing phenomenon, which occurs after thermal sintering process between the silicon and the rear contact aluminum layers due to their distinct material properties. The bowing depth increases exponentially along with the decrease of silicon layer thickness. Since excessive bowing yields irreparable damage to the cell panel, mitigating the bowing depth is essential for commercialization of the thin c-Si solar cells. Here, dominant factors affecting the solar cell bowing are explored to determine the optimal manufacturing conditions for minimizing the bowing displacement. Using a numerical procedure developed in our previous study including three layers of silicon, recrystallized, and aluminum, we performed a design of experiment (DOE) analysis on six important factors. We investigated the sensitivity of the selected parameters and their mutual correlations through the DOE analysis, followed by providing an equation for bowing depth prediction with additional stress-strain curve analysis among the solar cell sub-layers. The agreement of our prediction model with the experimental results was excellent in a broad range of silicon thickness. This study offers a basis for an appropriate design guideline for manufacturing thin c-Si solar cells.