Highly efficient and nearly roll-off-free electrofluorescent devices via multiple sensitizations

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Organic light-emitting diodes (OLEDs) suffer from efficiency roll-off at high luminance, limiting their widespread application.
• Achieving high quantum efficiency and rapid exciton decay simultaneously presents significant challenges in OLED design.

Purpose of the Study:

• To introduce a novel strategy, phosphor-assisted thermally activated delayed fluorescence (TADF)-sensitized fluorescence (TPSF), to address OLED efficiency roll-off.
• To enable high quantum efficiency and accelerated radiative exciton consumption in OLEDs.

Main Methods:

• Development of a phosphor-assisted TADF-sensitized fluorescence (TPSF) approach.
• Utilizing multiple sensitizations to disrupt singlet-triplet spin-flip cycles on a TADF host.
• Employing a TADF molecule with anti-accumulation-caused quenching characteristics.

Main Results:

• The TPSF strategy successfully achieves high quantum efficiency and rapid exciton consumption.
• A proof-of-concept device demonstrated a maximum external quantum efficiency (EQEmax) of 24.2%.
• The device achieved an ultrahigh L90% of 190,500 cd m⁻², indicating significantly improved operational stability at high luminance.

Conclusions:

• The TPSF strategy is a viable approach for overcoming efficiency roll-off in OLEDs.
• This method unlocks the potential of OLEDs for ultrahigh-luminance applications by enhancing both efficiency and stability.