Excitation energy transfer rate from Langmuir Blodgett (LB) dye monolayers to silicon: Effect of aggregate formation

Time-resolved emission spectra (TRES) and decay curves have been recorded from mixed LB oxacarbocyanine dye monolayers and stearic acid at different distances to the silicon surface. We observe interlayer energy transfer between monomers and dimers present in the monolayer competing directly with energy transfer to silicon at close distances. We resolve these competing processes by studying the TRES spectra and decompose them into their emission components. We found the energy transfer rate for the monomer to silicon to be double than that of the dimer at a distance of d ∼ 5 nm to the silicon surface. The Förster radius for the energy transfer to silicon was estimated at 5.5 ± 0.5 nm.