Spiro-fluorene locked multi-resonance delayed fluorescence helical framework: efficient circularly polarized...

Area of Science:

• Organic electronics
• Materials science
• Chiral optoelectronics

Background:

• Circularly polarized multiple resonance thermally activated delayed fluorescence (CP-MR-TADF) compounds exhibit excellent optical properties for chiral emitters.
• Limited molecular design strategies hinder the application of CP-MR-TADF in circularly polarized organic light-emitting diodes (CP-OLEDs).

Purpose of the Study:

• To develop novel molecular design strategies for CP-MR-TADF compounds.
• To improve the efficiency and color purity of chiral emitters in CP-OLEDs.

Main Methods:

• An intramolecular-locking strategy was employed, introducing a carbon bridge to fuse a tert-butyl carbazole moiety into the MR skeleton.
• A locking group with significant spatial hindrance, Spiro-3TCzBN, was incorporated.
• Optimized CP-OLEDs were fabricated using (P/M)-Spiro-3TCzBN emitters.

Main Results:

• The optimized CP-OLEDs achieved high maximum external quantum efficiencies of 34.6% and 34.9%.
• Clear circularly polarized electroluminescence signals were observed with electroluminescence dissymmetry factors of -3.51 × 10^-4 and +4.26 × 10^-4.
• Electroluminescence spectra remained stable across doping levels from 1 to 10 wt%.

Conclusions:

• The conformational locking strategy is effective for designing helicene-based chiral optical materials.
• Spiro-3TCzBN demonstrates potential as a chiral optical material for next-generation high-resolution CP-OLED displays.