Invited Paper: Luminescence Quenching by Charge Carriers in Organic Light-Emitting Diodes

We report photoluminescence quenching studies on model DCJTB-doped Alq(3) electroluminescent devices. The spectroscopy versus doping density suggests that solvatochromic effects are minor but that energy transfer plays a large role. Quenching of DCJTB fluorescence is due to Forster energy transfer to DCJTB cations, and measurements of the bleaching recovery dynamics show that charge extraction from ionized DCJTB sites is slow and consistent with biexponential kinetics. Temperature-dependent studies find effective activation barriers for detrapping that are too small to be consistent with simple HOMO offsets between host and dopant.