Efficient green electroluminescent devices with low operation voltage and slow efficiency roll-off by utilizing hole transport material as host

Abstract

We reported efficient electroluminescent (EL) devices with low operation voltage and slow efficiency roll-off based on green emitter Ir1 by utilizing hole transport material TAPC as host. Experimental results revealed our designed single light-emitting layer (EML) devices exhibit even lower operation voltage and slower efficiency roll-off compared with double-EMLs devices attributed to the reduced carriers' injection barriers, balanced carriers' distribution and well confined recombination zone. Ultimately, efficient green EL device realized the highest current efficiency (CE), power efficiency (PE), external quantum efficiency (EQE) and brightness of 71.6 cd/A, 75.0 lm/W, 22.9% and 36600 cd/m2, respectively. Excitedly, turn-on voltage was only 2.5 V. Even at a given brightness of 1000 cd/m2 (3.4 V), CE of 67.2 cd/A (EQE = 21.5%) and PE of 65.8 lm/W can still be retained. Our work offers a method to prepare efficient devices with slow efficiency roll-off, low operation voltage and simultaneously simple device structure.