Non-Destructive Contact Resistivity Measurements on Solar Cells Using the Circular Transmission Line Method

Several methods have been determined for measuring the contact resistivity of solar cell devices, but these methods are all either destructive in nature or require the fabrication of special metal contacts. In this paper, we present a non-destructive method for measuring the contact resistivity of commercial grade solar cells using the circular transmission line method. We first determine an optimal method for probing the total resistance of these structures on a solar cell and investigate the importance of measuring the exact dimensions of each contact. Then, by comparing the results of the measurement to traditional TLM results, we select a proper geometry for the circular patterns so that they can be hidden within the busbars of finished cells and not affect cell efficiency or aesthetic. Good correlation is demonstrated between automated circular TLM measurements performed on a new tool, the ContactSpot-PRO, and traditional TLM measurements performed manually. The implementation of this high-speed tool can allow contact resistance to be measured on every R&D or production cell with only a minor change in front silver paste screen artwork.