Excitation energy transfer efficiency of dipole–dipole interaction in a dye pair in polymer medium

Excitation energy transfer efficiency (η) of dipole–dipole interaction has been studied in the dye pair 3,3′-dimethyloxacarbocyanine iodide (DMOCI) (donor) to o-(6-diethylamino-3diethylimino-3H-xanthen-9-yl) benzoic acid (Rhodamine B, RB) (acceptor) in polyvinyl alcohol (PVA) thin films by steady-state and ps time-resolved fluorescence spectroscopy. In the presence of the acceptor the fluorescence intensity of the donor decreases, while that of the acceptor increases as a function of the added acceptor concentration. Time-resolved study of the donor at various acceptor concentrations suggest that the non-radiative energy transfer mechanism as proposed by Förster is responsible for the observed behaviour along with some modifications at very low acceptor concentrations. Modified η values have been simulated and compared with those obtained experimentally. It is found that the value of η increases with acceptor concentration.