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

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Abstract

The non-doped blue device with TPATPA-CNPPI shows luminance of 15 892 cd m ⁻², CE of 19.58 cd A ⁻¹, PE of 17.84 lm W ⁻¹, EQE of 8.96%, EUE of 73.40% and small roll-off efficiency (RO) of 1.11%.

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.

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Aggregation-Induced Emission: Together We Shine, United We Soar!

Ju Mei, Nelson Leung, Ryan T K Kwok … (2015)

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Highly efficient organic light-emitting diodes from delayed fluorescence.

Hiroki Uoyama, Kenichi Goushi, Katsuyuki Shizu … (2012)

The inherent flexibility afforded by molecular design has accelerated the development of a wide variety of organic semiconductors over the past two decades. In particular, great advances have been made in the development of materials for organic light-emitting diodes (OLEDs), from early devices based on fluorescent molecules to those using phosphorescent molecules. In OLEDs, electrically injected charge carriers recombine to form singlet and triplet excitons in a 1:3 ratio; the use of phosphorescent metal-organic complexes exploits the normally non-radiative triplet excitons and so enhances the overall electroluminescence efficiency. Here we report a class of metal-free organic electroluminescent molecules in which the energy gap between the singlet and triplet excited states is minimized by design, thereby promoting highly efficient spin up-conversion from non-radiative triplet states to radiative singlet states while maintaining high radiative decay rates, of more than 10(6) decays per second. In other words, these molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels, leading to an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency, of more than 19 per cent, which is comparable to that achieved in high-efficiency phosphorescence-based OLEDs.