Analysis of Solar Cell Electroluminescence Spectra for Daylight Inspection of c-Si PV Modules

As outdoor electroluminescence (EL) PV inspections are becoming more commercially available, this work has the objective to address the missing knowledge of what can be expected from the PV modules EL signal in the field, especially for daylight conditions, when the signal to be detected is very low in relation to the noise. Here we study the details of the EL emission spectral data statistics from each cell or representative selected cells in a PV module and verify that the crystalline silicon material characteristics of the solar cells are stable, even when faults were detected in EL image. Additionally, when comparing EL peak luminescence intensity of modules with different solar cell technologies, PERC modules where 9.7 and 14.5 times more intense than Al-BSF modules and the IBC module were 73.2% more intense, matching recent qualitative observations during outdoor luminescence imaging. The quantified results in absolute irradiance presented here will lead to the development of models for the prediction of the daylight EL imaging performance at different sunlight irradiance conditions, and for suggestions of optical filtering requirements during image acquisition.