A Comprehensive Evaluation of Contact Recombination and Contact Resistivity Losses in Industrial Silicon Solar Cells

Reliable characterization techniques to accurately quantify the metallization-induced recombination losses as well as contact resistivity losses of screen-printed cells are crucial for successful optimization of the contact grid design. Previously, the dark saturation current density at the contact ( {J}_{\rm 0c} ) is often assumed to be constant for different finger width. Similarly, impact of finger width on contact resistivity ( {\rho }_{\rm c} ) is rarely reported. Therefore, we performed a comprehensive evaluation of {J}_{\rm 0c} and {\rho }_{\rm c} as a function of finger width, spacing as well as firing temperature. We found out that {J}_{\rm 0c} increases from \approx 2000 to \approx 8100 \text{fA/cm}^{2} , when the finger width increases from 60 to 400 \mu m; and {\rho }_{\rm c} decrease from 7.2 to 2.2 \text{m}{\Omega }\cdot \text{cm}^{2} when using a wide-TLM rather than a narrow-TLM structure, for samples fired at 840 ^{\circ } C. Based on our cross-sectional and top-down scanning electron microscopy images, we believe that the physical root cause can be explained by the difference in the microstructure formed at the metal-silicon interface during the firing process for the screen-printed contacts.