Surface-plasmon-enhanced photoluminescence from metal-capped Alq_3 thin Films

摘要

Absolute quantum efficiencies of surface-plasmon-enhanced photoluminescence from Au capped Alq_3 films were measured using an integrating sphere. The metal "mirror" and directional enhancement effects due to surface roughness which usually occur in forward/backward collection measurements were eliminated using this integrating sphere technique. Up to 40% of the enhanced photoluminescence observed using the forward/backward collection method was shown to have come from mirror and/or enhanced directional scattering effects. Purcell factors obtained from the integrating sphere data and from time-resolved photoluminescence measurements were consistent, confirming surface-plasmon coupling. Incorporating a thin spacer layer enhanced the quantum efficiency and also eliminated nonradiative recombination due to the metal layer. The results clearly show the importance of using an integrating sphere when measuring overall surface-plasmon quantum efficiencies to eliminate directional scattering effects.