Uncertainty Assessment in the Measurement of Solar Cells under Standard Test Conditions

This study evaluates the uncertainty in current-voltage (I-V) performance testing of solar cells under Standard Test Conditions (STC) at the TÜV Rheinland solar cell testing laboratory in Shanghai, China. Several factors that could contribute to measurement uncertainty under STC are identified and analyzed, including electronic instrumental errors, temperature variability, optical effects, contact-related influences, and uncertainties arising from repeatability, reproducibility and data processing procedures. Methods are applied to analyze some sources of uncertainty, such as statistical analysis of experimental data, uncertainty budgets from instrument specifications, Monte Carlo simulations, and error propagation calculations from independent variable uncertainties. With spectral mismatch correction, the uncertainties for ISC, VOC and PMAX are determined to be 0.93% (k=2), 0.54% (k=2), and 1.68% (k=2) respectively. Without the correction for spectral mismatch, the uncertainties are determined to be 1.46% (k=2) for ISC, 0.54% (k=2) for VOC, and 2.02% (k=2) for PMAX respectively. The key factors influencing measurement uncertainty in solar cell I-V testing under STC conditions are identified. The outcomes of this study provide valuable guidance on optimizing measurement methods and controlling uncertainty budgets to stringent levels required by international testing standards.