High-performance organic light-emitting diodes with low-efficiency roll-off using bulky tetradentate [Pt(O^N^C^N)] emitters

High-performance organic light-emitting diodes (OLEDs) were realized by utilizing three robust platinum(II) complexes bearing tetradentate O^N^C^N ligands with a bridging tertiary amine (tetra-Pt-N), a biphenyl group with a spiro linkage (tetra-Pt-S) or a sterically encumbered 2,6-dimethyl-4-tert-butylphenyl moiety (tetra-Pt-M). By using a double-host emissive layer (EML) structure and a 10-nm-thick interlayer between the EML and the electron-transport layer (ETL), a maximum power efficiency of over 100 lm/W, a low turn-on voltage of less than 2.5 V and small efficiency roll-off were achieved. High external quantum efficiency (EQE) of 19.4% and 20.3% were maintained at 10000 cd/m2 in OLEDs with tetra-Pt-N and tetra-Pt-M, respectively. Such high efficiency at high luminance could be attributed to the effective suppression of triplet-triplet annihilation (TTA) in our optimized device structure.