Correlation of I-V Curve Parameters with Module-Level Electroluminescent Image Data Over 3000 Hours Damp-Heat Exposure

Four module brands of three samples each were exposed to 3000 hours of accelerated damp-heat testing. Current voltage (I-V) curve tracing and electroluminescent (EL) imaging were performed at 500 hour steps. The I-V curves were analyzed to get 8 common I-V parameters: maximum power (P
_mp
), fill factor (FF), current at maximum power (I
_mp
), voltage at maximum power (V
_mp
), current at short circuit (I
_sc
), voltage at open circuit (V
_oc
), series resistance (R
_s
), and shunt resistance (R
_sh
). The EL images were processed with a data processing pipeline using the open source coding language Python, employing techniques such as filtering, thresholding, convex Hull, regression fitting, and perspective transformation. This pre-processing was necessary to re-orient the images in a uniform manner as there was variance involved in the alignment of the modules during the measurement process. With the preprocessed data in hand, module-level parameters of median, mean, and standard deviation were calculated from the image pixel intensity distributions. These image data parameters were plotted against all the I-V curve parameters to identify trends in these data types. Correlation heat maps were generated depicting the relationships between data type parameters from IV and EL measurements.