Iridium Complexes Containing Three Different Ligands as White OLED Dopants

Abstract

Previously, we studied the luminescence characteristics of Ir(ppy)2(F2-ppy) and Ir(ppy)2(piq-F), which are heteroleptic iridium complexes involving two kinds of ligands, where F2-ppy, ppy and piq-F represent 2-(2,4-difluoro-phenyl)-pyridine, 2-phenylpyridine and 1-(4′-fluoroyphenyl)isoquinoline, respectively. Photoluminescence (PL) spectrum of Ir(ppy)2(F2-ppy) showed an emission peak at 495 nm in bluish green area. Ir(ppy)2(piq-F) showed two peaks at 513 nm and 600 nm in the PL spectrum. In order to make a white phosphorescent emitter for OLED, we herein designed a heteroleptic iridium complex containing three different ligands. We thought that reaction of F2-ppy, ppy and piq-F ligands all together with Ir(acac)3 might lead to Ir(F2-ppy)(ppy)(piq-F) among the mixture, displaying red and bluish green emission simultaneously. Ir(F2-ppy)(ppy)(piq-F) and other double-heteroleptic complex mixture are prepared from various concentration combination of ligands. The heteroleptic iridium complex mixture displays a variety of emission color, depending upon the combination ratio of ligands in the iridium complex synthesis. UV-vis absorption and photoluminescence (PL) spectra of the mixtures are analyzed and compared with the double-heteroleptic complexes. The white-yellow emission is observed when the mole ratio of ligands is 5:1:3 for F2-ppy, ppy and piq-F, respectively.