PHOTOLUMINESCENCE EFFICIENCY AND ABSORPTION OF ALUMINUM-TRIS-QUINOLATE (ALQ(3)) THIN-FILMS

Absorption, photoexcitation and internal and external luminescence eff iciencies for Alq(3) films grown by vacuum deposition have been measur ed accurately for the first time. The absorption spectrum measured at wavelengths between lambda = 250 and 450 nm is due to the overlap of t he (1)L(a) (385 nm) and B-1(b) (260 nm) transition bands found in the solution spectrum of Alq(3). The efficiency of the prominent luminesce nce band centered at lambda = 530 nm was observed to be independent of the excitation wavelength in the spectral range between lambda = 250 and 450 nm. The internal quantum efficiency was found to be (32 +/- 2) % independent of film thickness from 100 Angstrom to 1.35 mu m, indica ting a very short diffusion length for the (1)L(a), and B-1(b), excite d states.