Photoluminescence decay rate of an emitter layer on an Al nanocylinder array: effect of layer thickness

Photoluminescence (PL) of emitters on periodic arrays of plasmonic nanocylinders can be modulated largely by the interaction of the emitter with the plasmonic modes excited on the array. An energy transfer to metal, or nonresonant coupling of the emitters to high-order dark plasmonic modes, works as a nonradiative decay path to decrease the PL intensity. In this study, via PL decay rate measurements, we systematically investigated how the thickness of the emitter layer affected the energy transfer. An Eu complex was selected as an emitter, where Eu3+ acts as a light-emitting center with a high quantum yield. Thin layers of Eu complex showed an absorption coefficient of 3.4×104  cm−1, corresponding to the absorption length of 290 nm at a wavelength of 325 nm, i.e., the excitation wavelength used in this study. The thickness critically affected the energy transfer ratio, which was reduced as the thickness of the layers increased and was almost suppressed when the thickness was 1000 nm. The results suggest that there is an optimal thickness where PL enhancement is obtained with suppression of energy transfer.