Luminescence enhancement in microcavity organic multilayer structures

We have studied the photoluminescence properties of aluminum-tris(8-hydroxychinoline) (Alq3) and tris (4,4,4-trifluoro-1-(2-thienyl)-1,3-butanediono)-1,10-phenanthroline europium(III) (Eu(TTFA)3Phen) sandwiched between a planar Fabry-Perot microcavity structure. A strong influence of the position of the emission thin film on the luminescence spectra has been observed. The emission intensity normal to the substrate surface is drastically enhanced by an order of a magnitude if the active layer is placed at the antinode of the standing wave in the cavity. In comparison to non-resonant Alq3 structures, the full width at half-maximum (FWHM) of the spectrum is reduced from 100 to about 20 nm. We also show that the Eu(TTFA)3Phen luminescence is spatially directed due to the inherent linewidth of only 5 nm.