Thermally activated delayed fluorescence dyes featuring an intramolecular-locked azaryl ketone acceptor for electroluminescence application

We have developed two novel thermally activated delayed fluorescence (TADF) emitters, IQLO-PXZ and IQLO-DMAC, featuring an intramolecularly locked indeno[1,2-b]quinolin-11-one (IQLO) acceptor. Our comprehensive investigation, including structural analysis, theoretical calculations, and photophysical studies, aims to assess the viability of IQLO-PXZ and IQLO-DMAC as light emitters in electroluminescent devices. Unlike existing aryl ketone-based emitters, IQLO-PXZ and IQLO-DMAC exhibit red-shifted emission due to their structurally rigid and electron-deficient IQLO moiety. The stronger intramolecular charge transfer effect in IQLO-PXZ results in longer-wavelength emission compared to IQLO-DMAC. Both emitters demonstrate significant TADF properties, facilitating efficient triplet-to-singlet spin conversion. When utilized as the emissive core in electroluminescent devices, IQLO-PXZ and IQLO-DMAC achieved long-wavelength electroluminescence peaking at 612 nm and 578 nm, with commendable external quantum efficiencies of 10.3 % and 11.7 %, respectively. These findings underscore the potential of IQLO as an effective acceptor for constructing high-performance TADF electroluminescent materials.