The irregular domain and lack of ordering make it challenging to design deep neural networks for point cloud processing. This paper presents a novel framework named
Point Cloud Transformer
(PCT) for ...point cloud learning. PCT is based on Transformer, which achieves huge success in natural language processing and displays great potential in image processing. It is inherently permutation invariant for processing a sequence of points, making it well-suited for point cloud learning. To better capture local context within the point cloud, we enhance input embedding with the support of farthest point sampling and nearest neighbor search. Extensive experiments demonstrate that the PCT achieves the state-of-the-art performance on shape classification, part segmentation, semantic segmentation, and normal estimation tasks.
Nearly 100% triplet harvesting in conventional fluorophor‐based organic light‐emitting devices is realized through energy transfer from exciplex. The best C545T‐doped device using the exciplex host ...exhibits a maximum current efficiency of 44.0 cd A‐1, a maximum power efficiency of 46.1 lm W‐1, and a maximum external quantum efficiency of 14.5%.
High‐efficiency, thermally activated delayed‐fluorescence organic light‐emitting diodes based on exciplex emitters are demonstrated. The best device, based on a TAPC:DPTPCz emitter, shows a high ...external quantum efficiency of 15.4%. Strategies for predicting and designing efficient exciplex emitters are also provided. This approach allow prediction and design of efficient exciplex emitters for achieving high‐efficiency organic light‐emitting diodes, for future use in displays and lighting applications.
The recent introduction of thermally activated delayed fluorescence (TADF) emitters is regarded as an important breakthrough for the development of high efficiency organic light‐emitting devices ...(OLEDs). The planar D and A groups are generally used to construct TADF emitters for their rigid structure and large steric hindrance. In this work, it is shown that many frequently used nonaromatic (noncontinuous conjugation or without satisfying Hückel's rule) planar segments, such as 9,9‐dimethyl‐9,10‐dihydroacridine, are actually pseudoplanar segments and have two possible conformations–a planar form and a crooked form. Molecules constructed from pseudoplanar segments can thus have two corresponding conformations. Their existence can have significant impact on the performance of many TADF emitters. Two design strategies are presented for addressing the problem by either (1) increasing the rigidity of these groups to suppress its crooked form or (2) increasing the steric hindrance of the linked group to minimize energy of the emitters with the highly twisted form. Following these strategies, two new emitters are synthesized accordingly and successfully applied in OLEDs demonstrating high external quantum efficiencies (20.2% and 18.3%).
A schematic energy level diagram of (2‐(9,9‐dimethylacridin‐10(9H)‐yl) thianthrene‐5,5,10,10‐tetraoxide) shows that molecules constructed from pseudoplanar segments can have two corresponding conformations, which have significant impact on the performance of many thermally activated delayed fluorescence emitters. By either increasing the rigidity of these groups, or by increasing the steric hindrance of the linked group, the problem can be addressed.
A high‐efficiency single‐emission‐layer (EML) hybrid white organic light emitting device is fabricated based on an ideal sky‐blue fluorophor, DADBT, using a novel doping concentration regulation ...strategy, which effectively separates and respectively utilizes the singlet and triplet excitons in the single‐EML. The white device shows excellent electroluminescence performance with maximum total efficiencies of 26.6%, 53.5 cd A−1 and 67.2 lm W−1.
A novel molecular model of connecting electron‐donating (D) and electron‐withdrawing (A) moieties via a space‐enough and conjugation‐forbidden linkage (D‐Spacer‐A) is proposed to develop efficient ...non‐doped thermally activated delayed fluorescence (TADF) emitters. 10‐(4‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl) phenoxy) phenyl)‐9,9‐dimethyl‐9,10‐dihydroacridine (DMAC‐o‐TRZ) was designed and synthesized accordingly. As expected, it exhibits local excited properties in single‐molecule state as D‐Spacer‐A molecular backbone strongly suppress the intramolecular charge‐transfer (CT) transition. And intermolecular CT transition acted as the vital radiation channel for neat DMAC‐o‐TRZ film. As in return, the non‐doped device exhibits a remarkable maximum external quantum efficiency (EQE) of 14.7 %. These results prove the feasibility of D‐Spacer‐A molecules to develop intermolecular CT transition TADF emitters for efficient non‐doped OLEDs.
Non‐doped OLEDs: A novel molecular model of connecting electron‐donating (D) and electron‐withdrawing (A) moieties through a conjugation‐forbidden spacer is proposed to develop efficient thermally activated delayed fluorescence emitters for non‐doped organic light‐emitting diodes. The structure shows intermolecular charge‐transfer (CT) transitions as the major radiative channel and a suppressed effect of photoluminescence concentration quenching.
To develop high‐performance thermally activated delayed fluorescence (TADF) exciplex emitters, a novel strategy of introducing a single‐molecule TADF emitter as one of the constituting materials has ...been presented. Such a new type of exciplex TADF emitter will have two reverse intersystem crossing (RISC) routes on both the pristine TADF molecules and the exciplex emitters, benefiting the utilization of triplet excitons. Based on a newly designed and synthesized single‐molecule TADF emitter MAC, a highly efficient exciplex emitter MAC:PO‐T2T has been obtained. The device based on MAC:PO‐T2T with a weight ratio of 7:3 exhibits a low turn‐on voltage of 2.4 V, high maximum efficiency of 52.1 cd A−1 (current efficiency), 45.5 lm W−1 (power efficiency), and 17.8% (external quantum efficiency, EQE), as well as a high EQE of 12.3% at a luminance of 1000 cd m−2. The device shows the best performance among reported organic light‐emitting devices based on exciplex emitters. Such high‐efficiency and low‐efficiency roll‐off should be ascribed to the additional reverse intersystem crossing process on the MAC molecules, showing the advantages of the strategy described in this study.
A new type of high‐performance exciplex thermally activated delayed fluorescence TADF emitter is demonstrated by introducing single‐molecule TADF emitter as one of the constituting materials. The OLED based on the novel emitter shows a low turn‐on voltage of 2.4 V and a maximum external quantum efficiency of 17.8% with mild efficiency roll‐off, which offers a new strategy for designing efficient exciplex emitters.
Exciplex emitters have been extensively studied owing to their natural thermally activated delayed fluorescence characteristic, and many efforts have been made to improve their performance in organic ...light emitting diodes (OLEDs). In this work, the authors propose a novel strategy by introducing intermolecular hydrogen bond (HB) between electron‐donating and electron‐accepting constituting molecules (D and A) to suppress non‐radiative transition of exciplex emitters and thus improve their efficiencies and stabilities in the OLEDs. Accordingly, three exciplex emitters are constructed by using 1,3‐di(10H‐phenoxazin‐10‐yl)benzene (13PXZB) as donor and 4,6‐bis(3,5‐di(pyridin‐4‐yl)phenyl)‐2‐methylpyrimidine (B4PyMPM), 4,6‐bis(3,5‐di(pyridin‐3‐yl)phenyl)‐2‐methylpyrimidine (B3PyMPM), and 4,6‐bis(3,5‐di(pyridin‐2‐yl)phenyl)‐2‐methylpyrimidine (B2PyMPM) as acceptors. With the most intermolecular HBs, 13PXZB:B4PyMPM shows the highest photoluminescence quantum yield (69.6%) and the lowest rate constant of non‐radiative process of triplet excitons (3.4 × 105 S−1). And the OLED using 13PXZB:B4PyMPM as the emitter successfully exhibits a much higher external quantum efficiency of 14.6% than other contrastive devices. Moreover, the half lifetime of 13PXZB:B4PyMPM is 4.8 and 8.2 times higher than those of 13PXZB:B3PyMPM and 13PXZB:B2PyMPM in the devices. This work not only demonstrates that intermolecular HBs between D and A molecules can improve the performance of exciplex emitters, but also paves a new route to develop efficient and stable exciplex emitters.
A novel strategy is proposed to develop exciplex emitters by introducing an intermolecular hydrogen bond (HB) between electron‐donating and electron‐accepting constituting molecules, and a series of exciplex emitters are constructed accordingly. With the most intermolecular HBs, 1,3‐di(10H‐phenoxazin‐10‐yl)benzene:4,6‐bis(3,5‐di(pyridin‐4‐yl)phenyl)‐2‐methylpyrimidine successfully realizes the best efficiencies and stabilities in the organic light‐emitting diodes compared to other contrastive exciplex emitters.
A novel thermally activated delayed fluorescence (TADF) emitter 12,15‐di(10H‐phenoxazin‐10‐yl)dibenzoa,cdipyrido3,2‐h:2′,3′‐jphenazine (DPXZ‐BPPZ) is developed for a highly efficient red organic ...light‐emitting diode (OLED). With rigid and planar constituent groups and evident steric hindrance between electron‐donor (D) and electron‐acceptor (A) segments, DPXZ‐BPPZ realizes extremely high rigidity to suppress the internal conversion process. Meanwhile, the highly twisted structure between D and A segments will also lead to an extremely small singlet–triplet energy split to DPXZ‐BPPZ. Therefore, DPXZ‐BPPZ successfully realizes an efficient fluorescent radiation transition and reverse intersystem crossing process, and possesses an extremely high photoluminescence quantum efficiency of 97.1 ± 1.1% under oxygen‐free conditions. The OLED based on DPXZ‐BPPZ shows red emission with a peak at 612 nm and a Commission Internationale de L'Eclairage (CIE) coordinate of (0.60, 0.40), and it achieves high maximum forward‐viewing efficiencies of 20.1 ± 0.2% (external quantum efficiency), 30.2 ± 0.6 cd A−1 (current efficiency), and 30.9 ± 1.3 lm W−1 (power efficiency). The prepared OLED has the best performance among the reported red TADF OLEDs. These results prove that DPXZ‐BPPZ is an ideal candidate for red TADF emitters, and the designing approach is valuable for highly efficient red TADF emitters.
A thermally activated delayed fluorescence emitter with rigid and planar constituent segments and highly twisted electron‐donor–electron‐acceptor framework for highly efficient red organic light‐emitting diode is developed. It results in an efficient fluorescent radiation transition and reverse intersystem crossing process simultaneously. The device based on this emitter exhibits red emission as well as a high maximum forward‐viewing external quantum efficiency of 20.1 ± 0.2%.
Traditional Chinese medicine (TCM) has unique therapeutic effects for complex chronic diseases. However, for the lack of an effective systematic approach, the research progress on the effective ...substances and pharmacological mechanism of action has been very slow. In this paper, by incorporating network biology, bioinformatics and chemoinformatics methods, an integrated approach was proposed to systematically investigate and explain the pharmacological mechanism of action and effective substances of TCM. This approach includes the following main steps: First, based on the known drug targets, network biology was used to screen out putative drug targets; Second, the molecular docking method was used to calculate whether the molecules from TCM and drug targets related to chronic kidney diseases (CKD) interact or not; Third, according to the result of molecular docking, natural product-target network, main component-target network and compound-target network were constructed; Finally, through analysis of network characteristics and literature mining, potential effective multi-components and their synergistic mechanism were putatively identified and uncovered. Bu-shen-Huo-xue formula (BSHX) which was frequently used for treating CKD, was used as the case to demonstrate reliability of our proposed approach. The results show that BSHX has the therapeutic effect by using multi-channel network regulation, such as regulating the coagulation and fibrinolytic balance, and the expression of inflammatory factors, inhibiting abnormal ECM accumulation. Tanshinone IIA, rhein, curcumin, calycosin and quercetin may be potential effective ingredients of BSHX. This research shows that the integration approach can be an effective means for discovering active substances and revealing their pharmacological mechanisms of TCM.
PDF
