Cyclometalated Ir(III) Complexes for High-Efficiency Solution-Processable Blue PhOLEDs

This article reports the systematic functionalization of FIrpic (<b>1</b>) with solubilizing alkyl groups (complexes <b>2</b>–<b>4</b>) or mesityl groups (complexes <b>5</b> and <b>6</b>). Complex <b>5</b> is shown to offer significant advantages over FIrpic (<b>1</b>) in terms of performance of sky-blue polymer-based phosphorescent organic light-emitting diodes (PhOLEDs) with a solution-processed emitting layer (λ_max^EL 477 nm for <b>5</b>). Devices with <b>5</b> doped into poly­(vinylcarbazole) (PVK):OXD-7 gave a maximum luminous efficiency of 19.1 cd A^–1 at a brightness of 5455 cd m² with EQE 8.7%. Optimized multilayer devices with additional TPBi and LiF layers gave 23.7 cd A^–1 and EQE 10.4%. These data compare favorably with leading literature values for sky-blue polymer-based PhOLEDs. The enhanced performance of <b>5</b> is ascribed to three main reasons: (i) reduced concentration quenching of <b>5</b>; (ii) the higher radiative yield of <b>5</b>; and (iii) improved solubility of <b>5</b> in organic solvents. Complex <b>5</b> should find widespread use as a soluble blue phosphor for displays and lighting applications using solution processing techniques