Managing Excitons and Charges for High-Performance Fluorescent White Organic Light-Emitting Diodes

The simultaneous realization of high efficiency, stable spectra, high color rendering index (CRI), and low-efficiency roll-off in a fluorescent white organic light-emitting diode (WOLED) still remains a big challenge. Here, we demonstrate high-performance conventional fluorescent-dopant-based WOLEDs by strategic management of singlet and triplet excitons within an efficient emissive zone. This design consists of two separated red/green sub-EMLs with ultralow doping concentration and a sandwiched sub-EML doped with red and green fluorescent dyes at a relatively high concentration, which can harness all electrogenerated excitons and reduce the energy loss to the utmost extent. Accordingly, the resulting WOLED realizes an external quantum efficiency (EQE) of 18.2% with a maximum power efficiency of 44.6 lm W^-1. At the practical luminance of 1000 cd m^-2 for the lighting source, the EQE still remains as high as 16.2% with a CRI of 82 and stable color spectra. A comprehensive understanding of the device working mechanism is performed to guide design of efficient and stable fluorescent WOLEDs.