The performance of organic dyes in PMMA has been evaluated in a three-layer planar luminescent solar concentrator. The single plate and combined three-plate efficiencies have been measured for a number of dyes, and results of one typical combination are reported here. A detailed characterization of the spectroscopic properties of the dye molecules as well as the device dependent and device independent parameters of the plates allow comparison between measured and predicted efficiency. Our results demonstrate the presence of a significant positive synergism for the multilayer device.

The influence of self-absorption in a 4-dicyano-methylene-2-methyl-6-p-dimethyl amino-styrl-4H-pyran (DCM) doped polymethylmethacrylate (PMMA) optical waveguide on the light transport efficiency has been evaluated. A Monte Carlo technique was used to simulate intermolecular energy transfer and calculate the energy emission profile of an active waveguide. The calculated and measured edge emission profiles were found to be in excellent agreement. The edge emission spectra for various distances of excitation from the edge were used to estimate the DCM self-absorption cross section.

The effect of solvent medium on the measured lifetimes of the emitting states of several iridium(III) complexes is interpreted in terms of a model invoking *-* configuration interaction. The model yields an interaction parameter, 0, whose magnitude is 280 cm-1 as determined from measured energies and decay times of the as-dichlorobis(5,6-dimethyl-l,10phenanthroline)iridium(III) ion. A quantitative scheme for classifying the emitting states of a number of iridium(III) complexes as "charge transfer" or "ligand localized" is developed in terms of the magnitude of 0. Preparations of several iridium(III) complexes of methyl-substituted phenanthroline and bipyridine are reported. Absorption and emission spectra, lifetimes, and photoluminescence quantum yields of the complexes at 77°K are given.