Effect of partial shading on the performance of concentrated photovoltaics: a simulation and experimental study based on the double-diode model

In practical applications of concentrator photovoltaic (CPV) cells, partial shading has emerged as a critical factor affecting performance stability due to inherently non-uniform irradiance distribution. This paper develops a simulation model based on the double-diode equivalent circuit to systematically evaluate shading effects on CPV performance. The model is validated against experimental measurements under six shading conditions (0%, 10%, 30%, 50%, 70%, and 90%), achieving excellent agreement with relative deviations below 3% for maximum power prediction. The effects of partial shading are comprehensively analyzed in terms of irradiance distribution, voltage and current density profiles, and internal current flow pathways. Results reveal a distinct nonlinear relationship between geometric shading ratio and effective irradiance loss, highlighting the necessity of using actual irradiance loss as the performance indicator. Non-uniform photocarrier generation induced by shading disrupts voltage and current density balance, extends current transport paths, enhances lateral diffusion, and significantly increases series resistance, thereby intensifying energy losses. Key electrical parameters including short-circuit current and maximum output power exhibit nearly linear decrease with increasing irradiance losses. Under equal irradiance losses, different shading distributions result in negligible performance differences (Pmax deviation <1.2%), confirming that total irradiance loss is the dominant factor governing CPV performance degradation. These findings provide quantitative guidance for minimizing irradiance losses and optimizing current transport paths in building-integrated CPV systems.