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

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 (k(RISC)). Herein, a pure green MR-TADF material (nu-DABNA-CN-Me) with high k(RISC) of 10(5) s(-1) is reported. The key to success is introduction of cyano groups into a blue-emitting MR-TADF material (nu-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'eclairage 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.

Automated summary

A pure green MR-TADF material (nu-DABNA-CN-Me) with high k(RISC) of 10(5) s(-1) is reported, achieved by introducing cyano groups into a blue-emitting MR-TADF material (nu-DABNA). The organic light-emitting diode employing it as an emitter exhibits green emission with a small full-width at half-maximum and a high maximum EQE of 31.9%.