Dataset Information

Diarylboron-Based Asymmetric Red-Emitting Ir(III) Complex for Solution-Processed Phosphorescent Organic Light-Emitting Diode with External Quantum Efficiency above 28.

ABSTRACT: Organic light-emitting diodes (OLEDs) are one of the most promising technologies for future displays and lighting. Compared with the blue and green OLEDs that have achieved very high efficiencies by using phosphorescent Ir(III) complexes, the red OLEDs still show relatively low efficiencies because of the lack of high-performance red-emitting Ir(III) complexes. Here, three highly efficient asymmetric red-emitting Ir(III) complexes with two different cyclometalating ligands made by incorporating only one electron-deficient triarylboron group into the nitrogen heterocyclic ring are reported. These complexes show enhanced photoluminescence quantum yields up to 0.96 and improved electron transporting capacity. In addition, the asymmetric structure can help to improve the solubility of Ir(III) complexes, which is crucial for fabricating OLEDs using the solution method. The photoluminescent and oxidation-reduction properties of these Ir(III) complexes are investigated both experimentally and theoretically. Most importantly, a solution-processed red OLED achieves extremely high external quantum efficiency, current efficiency, and power efficiency with values of 28.5%, 54.4 cd A-1, and 50.1 lm W-1, respectively, with very low efficiency roll-off. Additionally, the related device has a significantly extended operating lifetime compared with the reference device. These results demonstrate that the asymmetric diarylboron-based Ir(III) complexes have great potential for fabricating high-performance red OLEDs.

SUBMITTER: Yang X

PROVIDER: S-EPMC5979779 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Diarylboron-Based Asymmetric Red-Emitting Ir(III) Complex for Solution-Processed Phosphorescent Organic Light-Emitting Diode with External Quantum Efficiency above 28.

Yang Xiaolong X Guo Haoran H Liu Boao B Zhao Jiang J Zhou Guijiang G Wu Zhaoxin Z Wong Wai-Yeung WY

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20180306 5

Organic light-emitting diodes (OLEDs) are one of the most promising technologies for future displays and lighting. Compared with the blue and green OLEDs that have achieved very high efficiencies by using phosphorescent Ir(III) complexes, the red OLEDs still show relatively low efficiencies because of the lack of high-performance red-emitting Ir(III) complexes. Here, three highly efficient asymmetric red-emitting Ir(III) complexes with two different cyclometalating ligands made by incorporating ...[more]

PMID: 29876224

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Project description:Cohosts based on hole transporting and electron transporting materials often act as exciplexes in the form of intermolecular charge transfer complexes. Indeed, exciplex-forming cohosts have been widely developed as the host materials for efficient phosphorescent organic light-emitting diodes (OLEDs). In host-guest systems of OLEDs, the guest can be excited by two competing mechanisms, namely, excitation energy transfer (EET) and charge transfer (CT). Experimentally, it has been reported that the EET mechanism is dominant and the excitons are primarily formed in the host first and then transferred to the guest in phosphorescent OLEDs based on exciplex-forming cohosts. With this, exciplex-forming cohosts are widely employed for avoiding the formation of trapped charge carriers in the phosphorescent guest. However, theoretical studies are still lacking toward elucidating the relative importance between EET and CT processes in exciting the guest molecules in such systems. Here, we obtain the kinetics of guest excitation processes in a few trimer model systems consisting of an exciplex-forming cohost pair and a phosphorescent guest. We adopt the Förster resonance energy transfer (FRET) rate constants for the electronic transitions between excited states toward solving kinetic master equations. The input parameters for calculating the FRET rate constants are obtained from density functional theory (DFT) and time-dependent DFT. The results show that while the EET mechanism is important, the CT mechanism may still play a significant role in guest excitations. In fact, the relative importance of CT over EET depends strongly on the location of the guest molecule relative to the cohost pair. This is understandable as both the coupling for EET and the interaction energy for CT are strongly influenced by the geometric constraints. Understanding the energy transfer pathways from the exciplex state of cohost to the emissive state of guest may provide insights for improving exciplex-forming materials adopted in OLEDs.

Dataset Information

Diarylboron-Based Asymmetric Red-Emitting Ir(III) Complex for Solution-Processed Phosphorescent Organic Light-Emitting Diode with External Quantum Efficiency above 28.

Publications

Diarylboron-Based Asymmetric Red-Emitting Ir(III) Complex for Solution-Processed Phosphorescent Organic Light-Emitting Diode with External Quantum Efficiency above 28.

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