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 (λem = 456 nm) in the solution and film states at ambient temperature. Moreover, this complex exhibits considerably high phosphorescent quantum efficiency (80%) and thermal stability (Td5 = 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.

Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands

“…In the last 5 years, luminescent Ir III -based species been extensively studied as biological labels, , photosensitizers for light-driven catalytic water reduction, singlet oxygen sensitizers, , sensors, , and highly efficient electroluminescent emitters for OLEDs. − In particular, the phosphorescent heteroleptic neutral Ir III -based cyclometalated complexes bearing bidentate N ∩ N ancillary ligands [Ir­(C ∩ N) 2 (N ∩ N)] (N ∩ N are amidinates and guanidinates, or β-diketoiminates; Figure A–C) have been used in photocatalytic, , optoelectronic, and photonic applications …”

Homoleptic Ir(III) Phosphors with 2-Phenyl-1,2,4-triazol-3-ylidene Chelates for Efficient Blue Organic Light-Emitting Diodes

“…Relevant Ir­(III) emitters were also tested for OLED fabrications and other optical applications. − With an aim of expanding phosphor designs, we envisaged the possibility of using 1,2,4-triazolylidene cyclometalates C-V for construction of luminescent metal complexes that have never been documented in the literature. The C-V chelate is also akin to the closely related 5-phenyl-1,2,4-triazolyl chelate ( C-VI ) and analogues that utilize a N-donor to coordinate to the metal center. − Some optoelectronic applications have been reported for Ir­(III) emitters bearing 5-phenyl-1,2,4-triazolyl chelate in recent days, which were specifically used for blue emitters. − …”

Theoretical investigation of the influence of heterocycles on the radiative and non-radiative decay processes of iridium(iii) complexes

“…aExperimental data is obtained from ref. 25.bThe emission wavelengths in brackets are calculated by the B3LYP functional.…”

“…aThe experimental data is obtained from ref. 25. Radiative decay constant, κ r = Φ / τ ; Non-radiative decay constant, κ nr = κ r (1/ Φ − 1).…”