Should Anisotropic Emission or Reabsorption of Nanoparticle Luminophores Be Optimized for Increasing Luminescent Solar Concentrator Efficiency?

Abstract

For the optimization of solar-to-electricity conversion efficiency of luminescent solar concentrators (LSCs), luminophores are treated as isotropic emitters. As rod-shaped nanocrystals are being developed, their anisotropic emission properties may be beneficial for LSC efficiency, as it is expected that escape cone losses can be reduced by proper alignment of nanorods (NRs). Herein, theoretical considerations and Monte Carlo ray-tracing simulations are used to examine the effect of anisotropic emission of luminophores on LSC performance, using nonspherical nanoparticles. Three different nanoparticles are examined with different Stokes shift and with two different quantum yield (QY) values (QY = 1 and QY = 0.7). In the case of a rod-shaped emitter with emission intensity distribution (Formula presented.) aligned perpendicular to the lightguide plane, escape cone losses can potentially be reduced to ≈9%, compared to 25.5% for isotropic emission. For more realistic anisotropic emitters, escape cone losses reduce to ≈19%. Nonetheless, it is found that the useful emission of isotropic quantum dots with low reabsorption is much larger than that of aligning anisotropic emitting NRs with high reabsorption. Hence, focus on reducing reabsorption loss yields larger improvements in LSC device efficiency than focus on aligned NRs.