White polymer light‐emitting diodes co‐doped with phosphorescent iridium complexes bearing the same cyclometalated ligand

Abstract

AbstractIn order to develop white organic light‐emitting devices, we fabricated poly(9‐vinylcarbazole)‐based polymer light‐emitting diodes (PLEDs) using blue‐ and orange‐phosphorescent bis‐cyclometalated iridium(III) complexes Ir‐1a and Ir‐1b as emitting co‐dopants, both of which possess the same cyclometalated ligand. The PLED co‐doped with Ir‐1a and Ir‐1b in a single emitting layer (WPLED‐1) yielded the optimized white electroluminescence with a Commission Internationale de L'Eclairage (CIE) chromaticity coordinate of (0.33, 0.46), although the value of the color rendering index (CRI) was very poor (CRI = 58). Thus, in order to improve the color rendering properties of WPLED‐1, the deep red‐phosphorescent iridium(III) complex Ir‐2 was employed as an additional co‐dopant. In the PLED co‐doped with Ir‐1a, Ir‐1b and Ir‐2 (WPLED‐2), tuning the ratio of the three emitting co‐dopants allowed us to obtain white electroluminescence with high color rendering properties (CRI = 82), where the CIE chromaticity coordinate of (0.38, 0.44) was obtained. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)