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

Abstract 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.