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We have prepared complexes of formula [Eu(beta-diketonate)(3)(DPEPO)] and shown quantitative excited-state energy transfer from the ligands combined with efficient Ln luminescence leading to exceptionally-high total photoluminescence quantum yield of up to 80% in solution and in PMMA.

The effects of excitation wavelength on the optical properties (emission spectrum and quantum yield) of a luminescent solar concentrator (LSC) containing a fluorescent organic dye (Lumogen F Rot 305) are studied. Excitation at wavelengths on the long-wavelength edge of the absorption spectrum of the dye results in redshifted emission, but the quantum yield remains constant at 100%. The origin of this effect and its consequences are discussed. The extent of the long-wavelength tail of the absorption spectrum of the dye is determined and the importance in reabsorption losses is shown. The optical efficiencies and photon transport probabilities of LSCs containing either an organic dye or a rare-earth lanthanide complex are compared using ray-tracing simulations and experiment. The optical efficiency is shown to depend strongly on the Stokes shift of the fluorophore. The lanthanide complex, which has a very large Stokes shift, exhibits a higher optical efficiency than the dye (64% cf. 50%), despite its lower quantum yield (86% cf. 100%).

The surface and edge emissions from dye-filled and dye-topped polycarbonate and polymethyl methacrylate luminescent solar concentrators were measured. We demonstrate that about 40-50% of the absorbed light energy (and 50-70% of the photons) is lost through the top and bottom surfaces of the filled waveguide. In most cases the escape cone losses are greater at the top than the bottom surface.

We describe the synthesis of a dye based on a perylene perinone and evaluate its potential as the functional material for use in the luminescent solar concentrator (LSC). The dye extends the absorption wavelength of LSCs using the perylene-based dye Lumogen Red 305 by more than ~50 nm, translating into the collection of potentially 25% more photons at a reasonable fluorescent quantum yield and photostability. When the new perinone is used in a two-waveguide LSC in conjunction with Red 305, the integrated edge emission of the total LSC system may be increased more than 24% when compared to the Red 305 dye alone.

No abstract

Organically functionalised supertetrahedral clusters: Two novel coordination polymers, consisting of chiral helical nanotubes and of composite layers, have been obtained by linkage of gallium-sulfide supertetrahedral clusters and dipyridyl ligands (see picture).

A Quantum Dot Solar Concentrator (QDSC) is based on the Luminescent Solar Concentrator (LSC), a concept first introduced in the 1960s 1 . LSCs consist of a flat plate of polymer material doped with a luminescent dye. A percentage of incident insolation, absorbed and re-emitted by the dye molecules is trapped inside the plate by total internal reflection. Reflective material situated on three of the edges and the back surface increases the trapping efficiency of the plate. Through successive reflection events light is concentrated onto a photovoltaic (PV) cell positioned on the fourth edge of the plate. Degradation of luminescent dyes prevented LSCs from being fully developed. A QDSC replaces luminescent dyes with semiconductor nanocrystals known as quantum dots (QDs) 2 . Passivation of QD cores with shells of higher band gap material is expected to provide increased stability 3 . QDs offer further advantages such as broad absorption spectra to utilize more of the solar spectrum and size tunability that allows spectral matching of the QDs emission to the peak efficiency of PV cells. Small-scale QDSCs have been fabricated using QDs bought commercially. The QDs have an emission wavelength of 600nm, close to the peak efficiency of a typical silicon PV cell. The systems were electrically characterized using a 4 cm monocrystalline PV cell optically matched to the QDSC edge with silicon oil. To investigate the effect of shape and size on concentrator efficiency, four different sized quadratic, two triangular and three circular QDSCs of various diameters were fabricated.