Stable pure-blue hyperfluorescence organic light-emitting diodes with high-efficiency and narrow emission

Organic light-emitting diodes (OLEDs) are a promising light-source technology for future generations of display^1,2. Despite great progress^3–12, it is still challenging to produce blue OLEDs with sufficient colour purity, lifetime and efficiency for applications. Here, we report pure-blue (Commission Internationale de l’ Eclairage (CIE) coordinates of 0.13, 0.16) OLEDs with high efficiency (external quantum efficiency of 32 per cent at 1,000 cd m⁻²), narrow emission (full-width at half-maximum of 19 nm) and good stability (95% of the initial luminacnce (LT₉₅) of 18 hours at an initial luminance of 1,000 cd m⁻²). The design is based on a two-unit stacked tandem hyperfluorescence OLED with improved singlet-excited-state energy transfer from a sky-blue assistant dopant exhibiting thermally activated delayed fluorescence (TADF) called hetero-donor-type TADF(HDT-1) to a pure-blue emitter. With stricter control of device fabrication and procedures it is expected that device lifetimes will further improve to rival commercial fluorescent blue OLEDs. © The Author(s), under exclusive licence to Springer Nature Limited 2021