Bright and Efficient, Non‐Doped, Phosphorescent Organic Red‐Light‐Emitting Diodes

Publisher Website
Google Scholar
Abstract
Ir(III)metal complexes with formula [(nazo)2Ir(Fppz)] (1), [(nazo)2Ir(Bppz)] (2), and [(nazo)2Ir(Fptz)] (3) [(nazo)H = 4‐phenyl quinazoline, (Fppz)H = 3‐trifluoromethyl‐5‐(2‐pyridyl) pyrazole, (Bppz)H = 3‐t‐butyl‐5‐(2‐pyridyl) pyrazole, and (Fptz)H = 3‐trifluoromethyl‐5‐(2‐pyridyl) triazole] were synthesized, among which the exact configuration of1was confirmed using single‐crystal X‐ray diffraction analysis. These complexes exhibited bright red phosphorescence with relatively short lifetimes of 0.4–1.05 μs in both solution and the solid‐state at room temperature. Non‐doped organic light‐emitting diodes (OLEDs) were fabricated using complexes1and2in the absence of a host matrix. Saturated red electroluminescence was observed at λmax = 626 nm (host‐emitter complex 1) and 652 nm (host‐emitter complex 2), which corresponds to coordinates (0.66,0.34) and (0.69,0.31), respectively, on the 1931 Commission Internationale de l'Eclairage (CIE) chromaticity diagram. The non‐doped devices employing complex 1showed electroluminance as high as 5780 cd m–2, an external quantum efficiency of 5.5 % at 8 V, and a current density of 20 mA cm–2. The short phosphorescence lifetime of1in the solid state, coupled with its modest π–π stacking interactions, appear to be the determining factors for its unusual success as a non‐doped host‐emitter.