Correlative Raman–Voltage Microscopy Revealing the Localized Structure–Stress Relationship in Silicon Solar Cells

Knowledge of localized strain at the micrometer scale is essential for tailoring the electrical and mechanical properties of ongoing thinning of crystal silicon (c-Si) solar cells. Thinning c-Si wafers below 110 μm are susceptible to cracking in manufacturing due to the nonuniform stress distribution at a micrometer region, necessitating a rigorous technique to reveal the localized stress distribution correlating with its device electrical output. In this context, a Raman microscopy integrated with a photovoltage mapping setup with high resolution to the submicrometer scale is developed to acquire correlative Raman-voltage of the localized physical properties at the microcracks on the rear side of c-Si solar cells. By integrating photoelectrical, mechanical, and theoretical simulations, we elucidated the evolution of the microcracks. The localized stresses cause significant electrical output degradation in c-Si solar cells. In addition, theoretical simulations and experimental characterization indicate that the etched rear side acts as a more intense stress concentrator, resulting in an asymmetrical stress distribution between the rear and front sides of c-Si solar cells. This finding provides valuable insights into the origin of microcracks in c-Si solar cells and serves as a metrology tool for microscale mapping of strain-engineered photovoltaic modules.