Tetradentate Pt(II) Complex as Phosphorescent Sensitizer for Highly Efficient Green Organic Light-Emitting Diodes with Low Efficiency Roll-Off

Tetradentate Pt(II) complex (Pt-Trz)-sensitized green fluorescent organic light-emitting-diodes (OLEDs) are developed to improve the external quantum efficiency (EQE) of a green fluorescent emitter (PhtBuPAD). Pt(II) complex and a green fluorescent emitter with bulky blocking units are chosen to efficiently manage energy transfer in phosphor-sensitized OLEDs. The Pt-Trz phosphor-sensitized fluorescent OLED with 2 wt% PhtBuPAD exhibits high EQE of 24.2% and maintains high EQE of 23.4% at a luminance of 3000 cd m⁻², realizing low efficiency roll-off of 3.8%. Moreover, high EQE is achieved even at a high PhtBuPAD-doping concentration of 3 wt%. In addition, the 2 wt% PhtBuPAD-doped phosphor-sensitized device achieves high maximum power efficiency of 91.1 lm W⁻¹, one of the highest power efficiencies among existing green sensitized devices. This study demonstrates that Pt-Trz phosphor-sensitized devices with an excellent triplet exciton utilization ability can achieve high EQE, low efficiency roll-off, and weak doping concentration quenching simultaneously.