Green-light

Common emitter

Photochemistry

Materials science

Layer (electronics)

Atomic physics

Quantum yield

Physics

Quantum efficiency

Nanotechnology

Optics

Blue light

Singlet state

Fluorescence

Bathochromic shift

Excited state

OLED

Chemistry

Intersystem crossing

Optoelectronics

Advanced Materials

Multiple resonance (MR)-effect-induced thermally activated delayed fluorescence (TADF) materials have garnered significant attention because they can achieve both high color purity and high external quantum efficiency (EQE). However, the reported green-emitting MR-TADF materials exhibit broader emission compared to those of blue-emitting ones and suffer from severe efficiency roll-off due to insufficient rate constants of reverse intersystem crossing process (kRISC ). Herein, a pure green MR-TADF material (ν-DABNA-CN-Me) with high kRISC of 105 s-1 is reported. The key to success is introduction of cyano groups into a blue-emitting MR-TADF material (ν-DABNA), which causes remarkable bathochromic shift without a loss of color purity. The organic light-emitting diode employing it as an emitter exhibits green emission at 504 nm with a small full-width at half-maximum of 23 nm, corresponding to Commission Internationale d'Éclairage coordinates of (0.13, 0.65). The device achieves a high maximum EQE of 31.9% and successfully suppresses the efficiency roll-off at a high luminance.

Development of Pure Green Thermally Activated Delayed Fluorescence Material by Cyano Substitution