Diffuse radiation influence on the performance of luminescent solar concentrators

Abstract

Luminescent Solar Concentrators (LSCs) are often purported to perform pretty well under both direct and diffuse solar irradiance conditions, yet the underlying rationale supporting this assumption remains scant. Furthermore, a significant portion of previous research on these photovoltaic devices relies on indoor equipment for efficiency characterization, thereby limiting insights into their performance under real operating conditions. In this study, we provide a theoretical framework elucidating the principles governing the superior performance of LSCs under diffuse irradiance. Specifically, we demonstrate that the isotropic distribution of dipoles within the LSC optical window aligns favorably with the Lambertian distribution of diffuse radiation, thereby enhancing photon absorption under diffuse conditions (25 %) respect to clear sunny skies (21 %). This theoretical foundation is bolstered by experimental investigations involving prototypes utilizing Lumogen Red dye, conducted under adverse irradiance conditions, including sunny, hazy, and partially cloudy skies. Our experimental findings reveal that light scattering, whether arising naturally from diffuse radiation or via scattering from neighboring surfaces, significantly amplifies the short-circuit current of LSC devices (37 % relative enhancement) compared to that generated under clear sky conditions (21 % relative enhancement).