Progress in module level quantitative electroluminescence imaging of crystalline silicon PV module: A review

Abstract

Electroluminescence (EL) imaging is a prominent tool for obtaining qualitative and quantitative information of defects and degradations in a crystalline silicon (c-Si) PV module. Quantitative EL imaging is an emerging field in which the impact of defects and degradation on module performance is evaluated from the EL images. However, the literature lacks an illuminated discussion on quantitative EL imaging compared to qualitative applications and implementation aspects of EL imaging. This article aims to provide one-stop information and a comprehensive review of advancements in module-level quantitative EL imaging. The state-of-art quantitative EL methods evaluating the module level impact of optical, bulk, series resistance, and shunting-related defects and degradations are reviewed. Each method has been critically assessed based on the approach of quantification, input EL imaging requirements, and performance of quantification. The outcome of the conducted assessment is concisely presented in the comparative table. It highlights the key achievements, advantages, and limitations of each method. Suggestions for future work are given to enhance quantification performance and overcome existing limitations for each method. Indoor and outdoor applicability for all the methods is briefly discussed, and on-field challenges are outlined considering the present use of outdoor EL imaging. Further, a comparative discussion of quantitative EL methods is presented for each category of defects and degradation to summarize the present stage of research, underlying research gaps, and future scope of work. This review paper would be instrumental for the future progress of quantitative EL imaging and its possible use in indoor or outdoor conditions.