A triphenylacrylonitrile phenanthroimidazole cored butterfly shaped AIE chromophore for blue and HLCT sensitized fluorescent OLEDs

Abstract

We have synthesized butterfly shaped emitters, TPATPA-PPI and TPATPA-CNPPI, having a hybridized local and charge-transfer (HLCT) emissive state with a hot exciton channel to harvest high-lying triplet excitons (T_n) through reverse intersystem crossing (h_RISC). The non-doped blue device with TPATPA-CNPPI shows a luminance (L) of 15 892 cd m⁻², a CE of 19.58 cd A⁻¹, a PE of 17.84 lm W⁻¹, an EQE of 8.96%, an EUE of 73.40% and a small roll-off efficiency (RO) of 1.11%. We also reported efficient HLCT sensitized fluorescent (HLCT-SF) OLEDs based on the HLCT material with TPATPA-CNPPI as the host and C545T as the dopant. The HLCT-SF device with TPATPA-CNPPI:1.0% C545T shows a luminance of 26 248 cd m⁻², a CE of 30.35 cd A⁻¹, a PE of 28.63 lm W⁻¹, an EQE of 10.03%, a RO of 2.69% and an EUE of 58.9%. The HLCT-SF process with FRET from the host harvested maximum dark triplet excitons via h_RISC effectively and enhanced the efficiency.