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A Silanea??based Bipolar Host with High Triplet Energy for High Efficiency Deepa??Blue Phosphorescent OLEDs with Improved Device Lifetime
摘要： A high triplet energy host is developed using silane moiety. 9-(4-(triphenylsilyl)dibenzo[b,d]furan-2-yl)-9H-carbazole (SiDBFCz) is designed through extensive density functional theory (DFT) calculations to obtain appropriate hole and electron injection barriers. The chemical hardness and the charge transport characteristics are comprehensively investigated to realize a bipolar host with high triplet energy over 2.9 eV for deep blue phosphorescent organic light-emitting diodes (PHOLEDs). The synthesized SiDBFCz clearly exhibits the bipolar characteristics especially with emitter molecules doped. An external quantum efficiency over 19% without any microcavity optimization is achieved thanks to the good charge balance in the SiDBFCz PHOLED. The device lifetime of the SiDBFCz PHOLED is improved more than 1000%, compared to the unipolar control devices at an initial luminance of 500 cd/m2. The dramatic enhancement of the operational stability of the deep blue PHOLED is also thoroughly investigated in terms of electrochemical stability of host molecules in charged or excited states. The results clearly indicate that the device lifetime is strongly correlated with the bond dissociation energy and the activation energy for the bond dissociation reaction in triplet excited state.
关键词： deep blue phosphorescent OLEDs,bond dissociation energy in triplet excited state,high triplet bipolar host,lifetime
更新于2025-09-16 10:30:52
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= 1,...,10)
摘要： Using fixed-node diffusion quantum Monte Carlo (DMC) simulation we investigate the structural properties and energetics of the linear and cyclic carbon clusters Cn for n (cid:2) 10. We calculate the binding energy, the electron correlation energy, the dissociation energy, and the second difference in energy. We also present an analysis of the structural properties of the clusters. It is found that the bond lengths, binding energies, and dissociation energies obtained from the DMC calculations are in excellent agreement with the available experimental results. The electron-correlation contribution to the binding energy indicates that in the case of the linear isomers, the clusters of odd-number size are relatively more favored than their neighbors of even-number size, whereas for the cyclic isomers, we do not observe the oscillation pattern. In the range of cluster size under investigation, we find that the electron-correlation impact in the binding energy of the cyclic clusters is larger than that of the corresponding linear ones, varying from 30% to 40% of the binding energy values. The electron correlation is also essential to the stability of the clusters enhancing by up to 52% their dissociation energy. A comparative analysis of the dissociation energy and second difference in energy indicates that the linear isomers C3 and C5 are the most stable ones.
关键词： dissociation energy,electron correlation,quantum Monte Carlo,carbon clusters,binding energy
更新于2025-09-04 15:30:14