Manus Kennedy

Luminescent Solar Concentrators - A review of recent results

Luminescent solar concentrators (LSCs) generally consist of transparent polymer sheets doped with luminescent species. Incident sunlight is absorbed by the luminescent species and emitted with high quantum efficiency, such that emitted light is trapped in the sheet and travels to the edges where it can be collected by solar cells. LSCs offer potentially lower cost per Wp. This paper reviews results mainly obtained within the framework of the Full-spectrum project. Two modeling approaches are presented, i.e., a thermodynamic and a ray-trace one, as well as experimental results, with a focus on LSC stability.

Modelling the Effect of Device Geometry on Concentration Ratios of Quantum Dot Solar Concentrators

Quantum dot solar concentrators (QDSCs) are static, non-imaging concentrators which concentrate both direct and diffuse light. Using Monte-Carlo ray-trace modelling, concentration ratios (C) were predicted for QDSCs of different 2-D geometries. The optimum shape and size were determined, for given system parameters, by calculating the relative cost per unit power output. Devices with different 3-D geometry were also compared. The thickness of the plate was varied and devices with tapered thickness were modelled to investigate the effect on C.

Down shifting in poly(vinyl alcohol) gels doped with terbium complex.

Novel poly(vinyl alcohol) (PVA) based soft gels with luminescent properties are detailed in this contribution. Lanthanide complex of terbium ions with anthranilic acid, Tb(ant)3·2H2O, was synthesized and incorporated into a DMSO/water solution, followed by addition of PVA, to attain soft gels at room temperature. Morphological and thermal analyses revealed homogeneous distribution of Tb(ant)3·2H2O into the PVOH/DMSO/water gel, and that incorporation of the terbium complex does not alter the thermal properties of the gels. The gels are transparent and luminescent, as they exhibit Large Stokes shift down shifting (LSS DS) up to 400nm, with very high emission quantum yield, that was found to be function of Tb complex concentration.

Thermoreversible luminescent organogels doped with Eu(TTA)3phen complex

This manuscript details the preparation and characterization of luminescent organogels in toluene. Gels were prepared by using 12-hydroxystearic acid (12HSA) as gelator and different amounts of thenoyltrifluoroacetonato 1,10-phenanthroline europium(III) complex (Eu(TTA)3phen). The gelation properties and the thermoreversible behavior from solid-like to liquid systems were investigated by differential scanning calorimetry. At higher concentration, an interaction of Eu complex with the polar group of the gelator was revealed by DSC and FTIR analyses. The spectroscopic behavior of the complex was investigated in toluene solution and in the gel state. TEM analysis revealed that 12HSA is able to solvate the Eu diketonate complex inducing a remarkable increase in the Eu-Eu distance. The Eu(TTA)3phen in the gel state exhibits a very high emission quantum yield, Φ, which was found to be independent of Eu complex concentration, at least for the composition range analyzed. These results indicate that 12HSA organogels containing Eu(TTA)3phen are promising materials for optical applications.

Ray-trace modelling of reflectors for quantum dot solar concentrators

Quantum Dot Solar Concentrators (QDSCs) are static, non-imaging concentrators which do not require expensive solar tracking and concentrate both direct and diffuse light. Optical efficiencies (ηopt) and concentration ratios (C) of a single plate QDSC were calculated by Monte-Carlo ray-trace modelling. Consideration of reflection, refraction, quantum dot (QD) photon emission and absorption and light attenuation in the device matrix were included in the analysis. In this paper, the effect of placing plane and diffuse reflectors at the rear surface was analyzed. Mirrors with a structured surface (saw-tooth shaped) were also modelled and the effect of each reflector type on C was determined, for direct and diffuse incident light. The diffuse and structured reflectors perform better than the plane reflector under direct light, but there is no significant difference under diffuse light. A spectrally selective reflector, placed at the top surface, reflects light emitted by QDs inside the escape cone back into the concentrator. For a particular set of model parameters, the model results show an increase in C of 13% due to the inclusion of a spectrally selective reflector.

Preparation and luminescence properties of organogel doped with Eu(TTA)3phen complex

In this contribution we report the preparation and the luminescence property of Eu(TTA)3phen complex doped toluene gels. Gels were prepared by using either a low molecular weight gelator, 12-hydroxystearic acid (HSA), or a macromolecular gelator, syndiotactic polymethylmethacrylate (s-PMMA). The gelation properties and their reversible behavior from solid-like to liquid systems have been investigated. In addition, photophysical investigations, as well as morphology, thermal properties and ageing behavior of the gels were analyzed as a function of composition of the gels.