Contactless Measurement of Current-Voltage Characteristics of Back-Contact Solar Cells

This study presents the application of a novel contactless method for measuring the current-voltage characteristics to interdigitated back contact (IBC) solar cells, addressing challenges associated with the rear metal contacts. The method involves a comprehensive characterization approach, utilizing reflectance and different photoluminescence measurements including partial illumination and different excitation wavelengths. Conventional contacted flash test measurements serve as a comparison. By implementing a simplified procedure with only two wavelengths for EQE, this technique enables accurate performance characterization without direct contact to the cell, reducing the risk of cell damage and measurement time. Results show a good average agreement with a strong correlation between contactless and traditional methods, particularly for the open-circuit voltage (Bravais-Pearson correlation R = 0.98) and efficiency (R = 0.78), while highlighting some discrepancies in the measurements of the short-circuit current density and the series resistance Rs, which may result from both the contacted and the contactless measurement. The pixel-wise application of the Rs determination offers insights into the lateral distribution of series resistance-induced losses and highlights opportunities for optimizing cell design. This research confirms the efficacy of the adapted contactless method for IBC cell characterization and demonstrates its potential for broader applications, especially in inline measurement processes. Further refinements can enhance the absolute accuracy of the method.