Superbly long lifetime over 13,000 h for multiple energy transfer channels in deep blue phosphorescence organic light-emitting diodes with Ir complex under CIEy of 0.17

Abstract

Despite over two decades of relentless endeavor, the industrial application of blue phosphorescent organic light-emitting diodes (PhOLEDs) has not been realized due to extremely short lifetime. The degradation of PhOLEDs is generally accelerated at high current levels since high triplet energy with long exciton lifetime are mostly concentrated on host molecules and transferred to dopant via slow Dexter energy transfer (DET) processes rather than fast Förster resonance energy transfer (FRET) processes. Herein, we propose a novel device architecture that creates multiple energy transfer channels by employing an Ir-complex intermediate energy carrier (IEC). Unlike exciplex or electroplex, no excitons were generated between the host and the IEC even though the IEC also behaves as a p-type host. The most crucial role of the IEC is to diversify the energy transfer channels. By introducing the IEC in deep blue PhOLEDs, both FRET and DET channels were additionally created between the IEC and the host, and the IEC and the dopant. Consequently, an unprecedentedly long half luminance lifetime of 13,830 h at an initial luminance of 100 cd/m2 was obtained with a high efficiency of 14.4% and CIEy = 0.17. To our best knowledge, the lifetime in our report is the longest with a deep blue phosphorescent Ir complex.