Optimization of Semiconductor Quantum Dots for Luminescent Solar Concentrators: Minimizing Reabsorption Losses

We investigate theoretically dependence of the reabsorption in semiconductor quantum dots (QDs) on their geometric and electron parameters, namely the radius r̅, its dispersion Δr̅ and bulk semiconductor band gap E
_g0
. QDs are promising as luminophores in luminescence solar concentrators (LSCs). The photo-luminescence (PL) process in QDs is influenced by the reabsorption. To understand how to minimize the detrimental reabsorption losses, we considered six semiconductors, typically used to fabricate QDs, with a wide range of their bulk bandgaps: CdS (E
_g0
= 2.42 eV), CdSe (E
_g0
= 1.67 eV), CdTe (E
_g0
= 1.5 eV), InP (E
_g0
= 1.27 eV), InAs (E
_g0
= 0.36 eV), and PbSe (E
_g0
= 0.27 eV). We prove that by adjusting the QD radius r̅ and dispersion Δr̅ , it is possible to optimize nanocrystal dimensions in order to minimize the reabsorption. It was shown that for the semiconductor bulk band gap in the range between 1.27 eV to 2.42 eV the optimum QD size and dispersion can always be chosen, at which the reabsorption is below the total experimental error of the measured normalized both absorption coefficient and luminescence intensity. Further reduction of Eg0, however, increases the reabsorption at any values of r̅ and Δr̅ : for instance, for PbSe based QD of 1 nm radius and its 1% dispersion, the reabsorption reaches 54%. We estimate the fragment of the solar spectrum, from which the photons, involved in the luminescence processes, originate. This is important for stacked LSCs application.