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Multiple Resonance Thermally Activated Delayed Fluorescent Emitters Based on Carbazole Fusion: A Qm/Mm Study

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SSRN 2024年

作者： Zhang, Kai He, Guanglu Lei, Cai Fan, Jianzhong Lin, Lili Wang, Chuan-Kui Li, Jing School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Shandong Province Key Laboratory of Medical Physics and Image Processing Technology School of Physics and Electronics Shandong Normal University Jinan250014 China

Multiple resonance (MR) type thermally activated delayed fluorescence (TADF) molecules are attracting attention for their narrowband emission, high luminescence efficiency, and high exciton utilization rate. Designing and studying these molecules has become an important direction for developing organic electroluminescent devices. Despite the significant potential in practical applications, developing long-wavelength emitting MR-TADF molecules remains a major challenge. This paper employs quantum mechanics/molecular mechanics (QM/MM) methods and the thermal vibration correlation function (TVCF) theory to study the luminescent properties of two MR-TADF molecules, asymmetric donor BNIP-tBuCz and symmetric donor BNDIP, in doped thin films. The calculations reveal that both molecules, while maintaining MR characteristics, possess small HOMO and LUMO energy gaps, enabling long-wavelength emission. Compared to BNIP-tBuCz, BNDIP has a slightly higher degree of conjugation and a greater proportion of π-π* transitions. Additionally, the transition dipole moment density and transition dipole moment in BNDIP are significantly enhanced, increasing the radiative rate. Both BNIP-tBuCz and BNDIP maintain similar porosity in thin films;however, BNIP-tBuCz is more sensitive to the aggregated environment. Stronger intermolecular interactions in BNDIP effectively suppress out-of-plane methyl wagging vibrations in low-frequency modes and C=C stretching vibrations in high-frequency modes, reducing reorganization energy and inhibiting the loss of non-radiative energy in the excited state. Furthermore, BNDIP's smaller energy gap between T1 and S1 (ΔEST) and its reorganization energy facilitate a faster reverse intersystem crossing rate (kRISC). Energy transfer characteristics are also studied using the semi-empirical Marcus theory. The calculated energy transfer rates of singlet and triplet states in BNIP-tBuCz are greater than those in BNDIP, due to the larger Gibbs free energy and excito

关键词： Energy transfer

Theoretical Study on the Influence of Substitution Position on the Luminescence Properties and Charge Transfer Characteristics of Thermally Activated Delayed Fluorescent Molecules

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SSRN 2023年

作者： Zhang, Kai Wang, XiaoFei Cai, Lei Fan, Jianzhong Wang, Chuan-Kui Lin, Lili School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Shandong Province Key Laboratory of Medical Physics and Image Processing Technology School of Physics and Electronics Shandong Normal University Jinan250014 China

Thermally active delayed fluorescence (TADF) molecules have potentially applications in organic light-emitting diodes (OLEDs) and biomedical sensing. Although TADF emitters have witnessed a rapid development, it remains challenging to study the relationship between molecular structures and luminescence properties as well as carrier mobility transfer properties in theory. In this work, the photophysical properties and luminescence mechanisms of isomers TPA-APQDCN-C (donors at para-position) and TPA-APQDCN-Y (donors at ortho-position) were studied based on density functional theory (DFT) and thermal vibration correlation function (TVCF) method. The results showed that both TPA-APQDCN-C with para-substitued donor and TPA-APQDCN-Y with ortho-substituted donors exhibit red emission in toluene and crystal state. Furthermore, compared to ortho-substituted donors, para-substituted donors promote a redshift in emission wavelength. In addition, the fluorescence efficiencies of TPA-APQDCN-C is obviously higher than that of TPA-APQDCN-Y due to its larger radiative rate and less non-radiative decay rate. Besides, para-substitution (TPA-APQDCN-C) leads to the smaller energy gap between and and the larger spin-orbit coupling (SOC) constant, which is beneficial for increasing the reverse crossing intersystem (RISC) rates. In addition, the carrier mobilities are studied based on the kinetic Monte Carlo simulations. The calculations show that TPA-APQDCN-C are more beneficial for the transfer of holes compared to TPA-APQDCN-Y. This study reveals TPA-APQDCN-C with donors at para-position has a better TADF properties and hole transfer ability, which holds guiding significance for the design of TADF devices with high luminescence efficiency and rapid hole transfer. © 2023, The Authors. All rights reserved.

关键词： Isomers

Efficient aerodynamic coefficients prediction with a long sequence neural network

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arXiv

arXiv 2024年

作者： Cai, A. Zemin Fan, B. Zhengyuan Liu, C. Tianshu Key Laboratory of Digital Signal and Image Processing of Guangdong Province Shantou China The Department of Electronic Engineering Shantou University Shantou China Department of Mechanical and Aerospace Engineering Western Michigan University KalamazooMI United States

Traditionally, deriving aerodynamic parameters for an airfoil via Computational Fluid Dynamics requires significant time and effort. However, recent approaches employ neural networks to replace this process, it still grapples with challenges like lack of end-to-end training and interpretability. A novel and more efficient neural network is proposed in this paper, called AirfoilNet. AirfoilNet seamlessly merges mathematical computations with neural networks, thereby augmenting interpretability. It encodes grey-scale airfoil images into a lower-dimensional space for computation with Reynolds number, angle of attack, and geometric coordinates of airfoils. The calculated features are then fed into prediction heads for aerodynamic coefficient predictions, and the entire process is end-to-end. Furthermore, two different prediction heads, Gated Recurrent Unit Net(GRUNet) and Residual Multi-Layer Perceptron(ResMLP), designed to support our iteratively refined prediction scheme. Comprehensive analysis of experimental results underscores AirfoilNet's robust prediction accuracy, generalization capability, and swift inference. Copyright © 2024, The Authors. All rights reserved.

关键词： Airfoils

Decomposing and Coupling Saliency Map for Lesion Segmentation in Ultrasound images

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arXiv

arXiv 2023年

作者： Ning, Zhenyuan Mao, Yixiao Feng, Qianjin Zhong, Shengzhou Zhang, Yu School of Biomedical Engineering Southern Medical University Guangdong Guangzhou510515 China Guangdong Provincial Key Laboratory of Medical Image Processing The Guangdong Province Engineering Laboratory for Medical Imaging and Diagnostic Technology Southern Medical University Guangzhou510515 China

Complex scenario of ultrasound image, in which adjacent tissues (i.e., background) share similar intensity with and even contain richer texture patterns than lesion region (i.e., foreground), brings a unique challenge for accurate lesion segmentation. This work presents a decomposition-coupling network, called DC-Net, to deal with this challenge in a (foreground-background) saliency map disentanglement-fusion manner. The DC-Net consists of decomposition and coupling subnets, and the former preliminarily disentangles original image into foreground and background saliency maps, followed by the latter for accurate segmentation under the assistance of saliency prior fusion. The coupling subnet involves three aspects of fusion strategies, including: 1) regional feature aggregation (via differentiable context pooling operator in the encoder) to adaptively preserve local contextual details with the larger receptive field during dimension reduction;2) relation-aware representation fusion (via cross-correlation fusion module in the decoder) to efficiently fuse low-level visual characteristics and high-level semantic features during resolution restoration;3) dependency-aware prior incorporation (via coupler) to reinforce foreground-salient representation with the complementary information derived from background representation. Furthermore, a harmonic loss function is introduced to encourage the network to focus more attention on low-confidence and hard samples. The proposed method is evaluated on two ultrasound lesion segmentation tasks, which demonstrates the remarkable performance improvement over existing state-of-the-art methods. Copyright © 2023, The Authors. All rights reserved.

关键词： Textures

Research on Monocular Depth Estimation Method based on Multi-Level Attention and Feature Fusion

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Research on Monocular Depth Estimation Method based on Multi...

IEEE Advanced Information Technology, Electronic and Automation Control Conference (IAEAC)

作者： Zhongyu Wu Hua Huang Qishen Li Penghui Chen School of Information Engineering Nanchang Hangkong University Nanchang Jiangxi China Key Laboratory of Jiangxi Province for Image Processing and Pattern Recognition Nanchang Jiangxi China School of Software Nanchang Hangkong University Nanchang Jiangxi China

Monocular depth estimation is a fundamental task in computer vision and has drawn increasing attention. Recently, attention-based models and encoder-decoder architectures have led to great improvements in monocular depth estimation. Typically, most of the previous methods used repeated simple up-sampling operations during decoding, which may not make full use of the potential properties of the features extracted by the encoder, and there are problems of inaccurate prediction of the edge and depth maximum region. We propose an attention-based feature fusion module for encoder and decoder. We treat the monocular depth estimation as a pixel-level optimization problem, where the coarsest encoder feature is used to initialize the pixel-level optimization, which is then refined to higher resolution by the proposed attentional feature fusion (AFF). We formulate the prediction problem as ordinal regression over the bin centers that discretize the continuous depth range. It predicts a correspondingly different distribution of bins based on different pictures and we predict bins at the coarsest level using global pooling and MLP layers. In the NYUV2 dataset, the proposed architecture improving original model by 2.5.% and 1.1%, in terms of Log10 and Absolute relative error, respectively.

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The Role of Bridging Groups in Regulating the Luminescence and Charge Transfer Properties of Thermally Activated Delayed Fluorescence Molecules: A Theoretical Perspective

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SSRN 2024年

作者： Zhang, Kai He, GuangLu Cai, Lei Fan, Jianzhong Lin, Lili Wang, Chuan-Kui Li, Jing School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Shandong Province Key Laboratory of Medical Physics and Image Processing Technology School of Physics and Electronics Shandong Normal University Jinan250014 China

organic emitters with a simultaneous combination of aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) characteristics are in great demand due to their excellent comprehensive performances toward efficient organic light-emitting diodes (OLEDs), biomedical imaging, and the telecommunications field. However, the development of efficient AIE-TADF materials remains a substantial challenge. In this work, light-emitting properties of two AIE-TADF molecules with different bridging groups ICz-BP and ICz-DPS are theoretically investigated in solid state with combined quantum mechanics/molecular mechanics (QM/MM) method and the thermal vibration correlation function (TVCF) theory. The research indicates that the C=O bridging bond in ICz-BP is more favorable than the S=O bridging bond in ICz-DPS for enhancing the planarity of the acceptor, increasing conjugation, and thereby elevating the transition dipole moment density. Simultaneously, the stacking pattern of ICz-BP in the solid facilitates a reduction in energy gap between S1 and T1 (ΔEST), achieving rapid reverse intersystem crossing rate (kRISC). Furthermore, compared to the toluene, the stacking patterns of ICz-BP and ICz-DPS in the solid effectively suppress the out-of-plane wagging vibration of the acceptor, thereby inhibiting the loss of non-radiative energy in the excited state and realizing aggregation-induced emission. Moreover, the charge transport properties of both electrons and holes in ICz-BP are found to be higher than the corresponding rates in ICz-DPS, attributed to the smaller internal reorganization energy of ICz-BP in the solid state. Additionally, the calculations reveal a more balanced charge transport characteristic in ICz-BP, contributing to efficient exciton recombination and emission, ultimately mitigating efficiency roll-off. Based on these computational results, we aim to unveil the relationship between molecular structure and light-emitting properties, aiding

关键词： Excited states

Multiple Resonance Thermally Activated Delayed Fluorescent Emitters Based on Carbazole Fusion: A Qm/Mm Study

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SSRN 2024年

作者： Zhang, Kai He, Guanglu Cai, Lei Fan, Jianzhong Lin, Lili Li, Jing Wang, Chuankui School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Shandong Province Key Laboratory of Medical Physics and Image Processing Technology School of Physics and Electronics Shandong Normal University Jinan250014 China

关键词： Energy transfer

A survey on negative transfer

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arXiv

arXiv 2020年

作者： Zhang, Wen Deng, Lingfei Zhang, Lei Wu, Dongrui the Key Laboratory of the Ministry of Education for Image Processing and Intelligent Control School of Artificial Intelligence and Automation Huazhong University of Science and Technology Wuhan430074 China the School of Microelectronics and Communication Engineering Chongqing University Chongqing400044 China

—Transfer learning (TL) utilizes data or knowledge from one or more source domains to facilitate the learning in a target domain. It is particularly useful when the target domain has very few or no labeled data, due to annotation expense, privacy concerns, etc. Unfortunately, the effectiveness of TL is not always guaranteed. Negative transfer (NT), i.e., leveraging source domain data/knowledge undesirably reduces the learning performance in the target domain, has been a long-standing and challenging problem in TL. Various approaches have been proposed in the literature to handle it. However, there does not exist a systematic survey on the formulation of NT, the factors leading to NT, and the algorithms that mitigate NT. This paper fills this gap, by first introducing the definition of NT and its factors, then reviewing about fifty representative approaches for overcoming NT, according to four categories: secure transfer, domain similarity estimation, distant transfer, and NT mitigation. NT in related fields, e.g., multi-task learning, lifelong learning, and adversarial attacks, are also discussed. Copyright © 2020, The Authors. All rights reserved.

关键词： Surveys

Effect of Hydrostatic Pressure on Room Temperature Phosphorescence Properties: A Theoretical Perspective

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SSRN 2024年

作者： Pang, Kunwei Xie, Zhen Lin, Lili Song, Yuzhi Wang, Chuan-Kui Fan, Jianzhong Xu, Yuanyuan Shandong Province Key Laboratory of Medical Physics and Image Processing Technology School of Physics and Electronics Shandong Normal University Jinan250014 China School of Science Qilu University of Technology Shandong Academy of Sciences Jinan250353 China

Development of stimulus-responsive RTP molecules becomes imperative. However, the inner responsive mechanism is unclear, theoretical investigations to reveal the relationship among hydrostatic pressures, molecular structures and photophysical properties are highly desired. Herein, based on the dispersion corrected density functional theory, the combined quantum mechanics and molecular dynamics method and thermal vibration correlation function theory, influences of hydrostatic pressure on molecular structures, transition properties as well as lifetimes and efficiencies of RTP molecule are theoretically studied. Results show that extended lifetime and enhanced efficiency are observed at 2 Gpa compared with molecule at normal pressure, and this is related with the small reorganization energy and large oscillator strength. Moreover, due to the small energy gap and remarkable spin-orbit coupling constant, fast intersystem crossing process is determined for molecule at 6 Gpa. Our work provides theoretical insights into the hydrostatic pressure response mechanism and could promote the development new efficient stimulus-responsive molecules. © 2024, The Authors. All rights reserved.

关键词： Hydrostatic pressure