Design, Synthesis, and Luminescence Applications of Acridone Derivatives

Abstract

Rationally tuning the emission position and narrowing the full width at half-maximum (FWHM) of an emitter is of great importance for many applications. By synergistically improving rigidity, strengthening the resonant strength, inhibiting molecular bending and rocking, and destabilizing the HOMO energy level, a deep-blue emitter (CZ2CO) with a peak wavelength of 440 nm and an ultranarrow spectral FWHM of 16 nm (0.10 eV) was developed via intramolecular cyclization in a carbonyl/N resonant core (QAO). The dominant υ₀₋₀ transition character of CZ2CO gives a Commission Internationale de I’Éclairage coordinates (CIE) of (0.144, 0.042), nicely complying with the BT.2020 standard. Moreover, a hyper-fluorescent device based on CZ2CO shows a high maximum external quantum efficiency (EQE_max) of 25.6% and maintains an EQE of 22.4% at a practical brightness of 1000 cd m^-2.

The steric hindrance of an emitter is of great importance for solid-state devices. Herein, a steric parameter of cone angle is introduced from the conventional organometallics to design and evaluated the emitters’ steric effect. Three multi-resonance thermal activated delayed fluorescence (MR-TADF) emitters with sp³ non-conjugated decorations are constructed. Theoretical and experimental investigation revealed that these emitters exhibit nearly identical ground and excited states. The devices incorporating emitters with high cone angle and significant rigidity exhibited the best concentration-resistant properties. The decent electroluminescence quantum efficiency (EQE) of up to 15.6% with an emission peak at 446 nm corresponds to a CIE of (0.150,0.117).

A new aggregation-induced emission (AIE) luminogens is obtained by dimerizing 9(10H)-acridone (Ac), an aggregation-caused quenching (ACQ) effect monomer via a N-N bond and forming 9H,9'H-[10,10'-biacridine]-9,9'-dione (DiAc) with D_2d symmetry. The quenching of DiAc in solution is ascribed to the enhanced basicity promoting hydrogen-bonding and then a hydrogen abstraction (HA) reaction and/or an unallowed transition in frontier orbitals with the same symmetry facilitating intersystem crossing. It was found that emissive Ac is one product in the non-emissive DiAc solution in HA reaction activated by UV irradiation. By exploiting the AIE properties and the HA reaction of DiAc, photolithographic patterning was demonstrated on a paper wetted with a DiAc solution.

Date of Award	21 Aug 2024
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Chun Sing LEE (Supervisor)