Tris(5‐phenyl‐1H‐1,2,4‐triazolyl)iridium(III) Complex and Its Use in Blue Phosphorescent Organic Light‐Emitting Diodes to Provide an External Quantum Efficiency of up to 27.8%

Abstract Although studies have investigated various N‐heterocyclic‐based Ir(III)‐cyclometalates that exhibit high efficiency and electrochemical stability, blue‐phosphorescent Ir(III) complexes with further improved efficiency and blue‐emission purity are needed for use as emitters in organic light‐emitting diodes (OLEDs). Therefore, the preparation and comprehensive characterization of a phenyl‐1,2,4‐triazole‐based facial‐homoleptic iridium(III) complex, TzIr (fac‐tris(1‐(2,6‐diisopropylphenyl)‐3‐methyl‐5‐phenyl‐1H‐1,2,4 triazolyl)iridium(III)) is herein described. The complex shows a definite blue‐emission band (λ_em = 456 nm) in the solution and film states at ambient temperature. Moreover, this complex exhibits considerably high phosphorescent quantum efficiency (80%) and thermal stability (T_d5 = 362 °C). Multilayer phosphorescent OLEDs using TzIr as the emitter and 3,3‐di(9H‐carbazol‐9‐yl)biphenyl (mCBP)/ 9‐(3′‐(9H‐carbazol‐9‐yl)‐5‐cyano‐[1,1′‐biphenyl]‐3‐yl)‐9H‐carbazole‐3‐carbonitrile (CNmCBPCN) as the mixed host are fabricated. The devices exhibit outstanding performance, with a high external quantum efficiency (27.8%), current efficiency (38.7 cd A⁻¹), and CIEy (y coordinate value of the Commission Internationale de l'Eclairage color space) less than 0.18. The results of this study indicate that this novel 1,2,4‐triazole‐based dopant, TzIr, is a promising candidate for developing highly efficient blue‐phosphorescent emitters for use in OLEDs.