Analysis of external quantum efficiency measurements of degraded solar cells embedded in solar modules

Abstract

External quantum efficiency (EQE) of a cell in a module provides insight into its operational performance, thus serving as an effective tool during failure analysis. However, accurately assessing the EQE of a degraded/non-degraded cell in a module is complex. The existing methodologies assume the cells to be identical in the module, which is not the case with actual PV modules, especially after the field exposure. Consequently, there is a need to establish the criteria for accurate EQE measurements if the cells are non-identical. This paper addresses this gap by demonstrating experimental results for different cases deviating from the ideal assumption of identical cells. The criteria for obtaining accurate EQE measurements for degraded and non-degraded cells in the modules are presented through experimental validation. Further, the feasibility of EQE measurement under outdoor conditions with sunlight as the bias light on a degraded, commercial, 60-cell PV modules was also demonstrated through experiments. This paper provides significant results for further development of this technique as an in-field, non-destructive diagnostic tool.