High-Efficiency Dual-Dopant Polymer Light-Emitting Diodes with Ultrafast Inter-fluorophore Energy Transfer

The integration of organic light-emitting diodes (OLEDs) into modern electronics has affirmed their role in next-generation display technologies, presenting advantages in energy efficiency, flexibility, large-area fabrication, and low-cost solution processability. Maintaining high luminance and color purity in OLEDs is an important goal, particularly for high-efficiency devices utilizing triplet excitons. Here, we report solution-processed dual-dopant polymer LEDs, in which highly efficient electroluminescence occurs via an intermolecular energy transfer from carbenemetal-amides (CMAs) (which exhibit rapid singlet-triplet interconversion) to a fluorescent rubrene derivative. This design enables solution-processed OLEDs with external quantum efficiencies of >20% (corresponding to near 100% internal quantum efficiencies) and a peak luminance of 75,000 cd m(-2). We show that the emission originates from the singlet state of the rubrene derivative. Ultrafast optical measurements indicate that the inter-fluorophore energy transfer occurs within 0.3 ps, at an efficiency of >96%. Such devices preserve the relatively narrow emission bandwidth of conventional fluorophores for color purity, showing potential in energy-efficient printable electronics.