Cyanopyridine Based Bipolar Host Materials for Green Electrophosphorescence with Extremely Low Turn-On Voltages and High Power Efficiencies

• DOI: 10.1021/acsami.6b04395
• Publication Date: 2016-08-01T18:36:47Z
• Authors: Wei Li; Jiuyan Li; Di Liu; Deli Li; Fang Wang
• Keywords: Quantum Efficiency; HOMO/LUMO; Electrical efficiency

Low driving voltage and high power efficiency are basic requirements when practical applications of organic light emitting diodes (OLEDs) in displays lighting considered. Two novel host materials m-PyCNmCP 3-PyCNmCP incorporating cyanopyridine moiety as electron-transporting unit developed for use fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) based green phosphorescent OLEDs (PhOLEDs). Extremely low turn-on voltages 2.01 2.27 V realized, which even lower than the theoretical limit emitted photon energy (hv)/electron charge (e) (2.37 V) Ir(ppy)3. High 101.4 lm/W (corresponding to a maximum external quantum 18.4%) 119.3 (24.7%) achieved PhOLEDs. The excellent EL performance benefits from ideal parameters by combining cyano pyridine enhance n-type feature. energetic favorable alignment HOMO/LUMO levels hosts with adjacent layers dopant easy injections direct trapping dopant, their bipolar feature balance transportations, sufficiently triplet small singlet/triplet difference (0.38 0.43 eV) combine be responsible extremely efficiencies