An orange iridium(iii) complex with wide-bandwidth in electroluminescence for fabrication of high-quality white organic light-emitting diodes

Abstract

A novel iridium(III) (pbi)₂Ir(biq) with a strong orange emission at 573 nm was synthesized, which showed a high photoluminescence quantum yield (PLQY) of 45% in CH₂Cl₂ at 298 K. The quantum chemical calculations together with the photophysical properties indicated that the transition incorporation of ³MLCT (metal-to-ligand charge transfer), ³LLCT (ligand-to-ligand charge transfer) mixed with ³LC (ligand-centered ³π–π*) characters contributed to the emission of (pbi)₂Ir(biq). Cyclic voltammetry (CV), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were then performed to investigate its electrochemical and thermal properties for fabrication of electroluminescent devices. Interestingly, complex (pbi)₂Ir(biq) exhibited wide-bandwidth in electroluminescence (EL) of its orange electroluminescent devices, which made it effectively available to fabricate high-quality two-element white organic light-emitting diodes (WOLEDs). The resultant WOLED possessed a high current efficiency (η_c) of 22.1 cd A⁻¹ and power efficiency (η_p) of 25.5 lm W⁻¹ with a high color rendering index (CRI) of 80. Especially, the WOLED retained a favorable η_p of 10.9 lm W⁻¹ and η_c of 16 cd A⁻¹ at a high luminance of 1000 cd m⁻². Moreover, it was worthwhile to note that this WOLED exhibited a qualified R9 of 13 and Duv of −0.0013, and these values together with the high CRI conformed to the required standard for lamp illumination of the ENERGY STAR.