Electro-Thermal Circuit Models of Photovoltaic Cells Subjected to Optical Degradation Phenomena

This paper presents an advanced electro-thermal modeling framework for photovoltaic (PV) cells subjected to optical degradation, with a specific focus on encapsulant discoloration phenomena. A modified single-diode model is developed, incorporating a temperature-dependent formulation of the photogenerated current based on semiconductor physics and spectral reflectance variations. The model establishes a closed-loop feedback mechanism between optical degradation, mismatching conditions, and localized thermal stress. Coupled simulations in PSIM and COMSOL Multiphysics are used to evaluate temperature distributions in a commercial mono-Si PV module under three scenarios: unexposed EVA, moderate yellowing, and severe discoloration. Results confirm the emergence of thermal hot spots, with peak temperatures reaching up to 111°C in degraded cells, consistent with experimental observations in the literature. The study underscores the importance of including optical aging effects in predictive thermal models to improve reliability assessment and system design in PV technologies.