Fundamental limits of concentration in luminescent solar concentrators revised: the effect of reabsorption and nonunity quantum yield

Luminescent solar concentrators (LSCs) are devices theoretically able to condense both direct and diffuse solar radiation into thin dielectric layers with extremely high efficiencies. A theory based on thermodynamic principles was developed in the past to estimate the concentration limits that can be achieved with an LSC and facilitate researchers’ efforts to predict the potential of their designs to convert optical to electrical power. However, while concentration efficiencies of thousands or even tens of thousands of suns are supported by this model, values of only a fraction of those have ever been recorded experimentally. This is because in the calculation of the thermodynamic limits the quantum yield of the luminophores is assumed to be equal to unity and any processes that quench the intensity of the trapped field are completely ignored. In an attempt to better match theory with reality and provide more accurate performance estimates, we have revised the limits of concentration based on a statistical optics framework. The new model gives insight into the main mechanisms inhibiting the concentration of LSCs and can be used to extract design rules for efficient LSCs. Comparisons between the method presented in this paper and results obtained with Monte Carlo ray-tracing simulations demonstrate excellent agreement between the two. Finally, we discuss the conditions for validity of the thermodynamic limits, and we show that in some circumstances these can actually be surpassed.