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

Abstract

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.