Blue to True-Blue Phosphorescent IrIII Complexes Bearing a Nonconjugated Ancillary Phosphine Chelate: Strategic Synthesis, Photophysics, and Device Integration

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Abstract
We report the design and synthesis of IrIII complexes functionalized with substituted pyridyl cyclometalate or azolate chromophores, plus one newly designed nonconjugated phosphine chelate, which not only greatly restricts its participation in the lowest-lying electronic transition but also enhances the coordination strength. These two key factors lead to fine-tuning of the phosphorescence chromaticity toward authentic blue and simultaneously suppress, in part, the nonradiative deactivation. This conceptual design presents a novel strategy in achieving heretofore uncommon, high-efficiency blue and true-blue phosphorescence. The fabrication of the organic light-emitting devices (OLEDs) employing phosphorescent dopants [Ir(dfpbpy)2(P∧N)] (1b) and [Ir(fppz)2(P∧N)] (3) was successfully made, for which the abbreviations (dfpbpy)H, (fppz)H, and (P∧N)H represent 2-(4,6-difluorophenyl)-4-tert-butylpyridine, 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole, and 5-(diphenylphosphinomethyl)-3-(trifluoromethyl)pyrazole, respectively. Of particular interest is the 3-doped OLEDs, which exhibit remarkable maximum efficiencies of 6.9%, 8.1 cd A−1, and 4.9 lm W−1, together with a true-blue chromaticity CIEx,y = 0.163, with 0.145 recorded at 100 cd m−2.

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