Highly efficient dual-dopant enhanced emission OLEDs

Abstract

The efficiency of OLEDs is fundamentally determined by the spin of excited state electrons. We have previously shown, using a new class of emissive molecules, carbene-metal-amides (CMA), an unusual emission pathway based on spin-state inter-conversion - intramolecular rotation induces a shift in the relative energies of the first excited singlet and triplet states, leading to extremely efficient singlet-triplet state interconversion and photoemission. In our recent work, we report solution-processed dual-dopant polymer LEDs, in which highly efficient electroluminescence occurs via an intermolecular energy transfer from CMAs to a fluorescent emitter. With electroluminescence from the simple fluorophore, we obtained record EQEs of >20% in these devices. Photophysical measurements indicate that ultrafast inter-fluorophore energy transfer occurs with near-unity efficiency. They preserve the relative colour purity of simple fluorophores, potential for energy-efficient printable electronics.