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[摘要]：Intriguing electroluminescence (EL) spikes, following a voltage pulse applied to small molecular OLEDs, are discussed, elucidating carrier and exciton quenching dynamics and their relation to device structure. At low temperatures, all devices exhibit spikes at similar to 70-300 ns and mu s-long tails. At 295 K only those with a hole injection barrier, carrier-trapping guest-host emitting layer, and no strong hole-blocking layer exhibit the spikes. They narrow and appear earlier under post-pulse reverse bias. The spikes and tails are in agreement with a revised model of recombination of correlated charge pairs (CCPs) and initially unpaired charges. Decreased post-pulse field-induced dissociative quenching of singlet excitons and CCPs, and possibly increased post-pulse current of holes that "turn back" toward the recombination zone after having drifted beyond it are suspected to cause the spikes' amplitude, which exceeds the dc EL. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3481687] |
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