Purely organic fluorescent materials that concurrently exhibit high efficiency, narrowband emission, and circularly polarized luminescence (CPL) remain an unaddressed issue despite their promising ...applications in wide color gamut‐ and 3D‐display. Herein, the CPL optical property and multiple resonance (MR) effect induced thermally activated delayed fluorescence (MR‐TADF) emission are integrated with high color purity and luminous efficiency together. Two pairs of highly efficient green CP‐MR‐TADF enantiomers, namely, (R/S)‐OBN‐2CN‐BN and (R/S)‐OBN‐4CN‐BN, are developed. The enantiomer‐based organic light‐emitting diodes (OLEDs) exhibit pure green emission with narrow full‐width at half‐maximums (FWHMs) of 30 and 33 nm, high maximum external quantum efficiencies (EQEs) of 29.4% and 24.5%, and clear circularly polarized electroluminescence (CPEL) signals with electroluminescence dissymmetry factors (gEL) of +1.43 × 10−3/−1.27 × 10−3 and +4.60 × 10−4/−4.76 × 10−4, respectively. This is the first example of a highly efficient OLED that exhibits CPEL signal, narrowband emission, and TADF concurrently.
Two pairs of circularly polarized multiple resonance thermally activated delayed fluorescence (CP‐MR‐TADF) enantiomers are developed by combining the merits of circularly polarized luminescence (CPL) and MR‐TADF. This is the first example of a highly efficient organic light‐emitting diode (OLED) that exhibits circularly polarized electroluminescence signal, narrowband emission, and TADF concurrently.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Despite much research progress in image semantic segmentation, it remains challenging under adverse environmental conditions caused by imaging limitations of the visible spectrum, while thermal ...infrared cameras have several advantages over cameras for the visible spectrum, such as operating in total darkness, insensitive to illumination variations, robust to shadow effects, and strong ability to penetrate haze and smog. These advantages of thermal infrared cameras make the segmentation of semantic objects in day and night. In this article, we propose a novel network architecture, called edge-conditioned convolutional neural network (EC-CNN), for thermal image semantic segmentation. Particularly, we elaborately design a gated featurewise transform layer in EC-CNN to adaptively incorporate edge prior knowledge. The whole EC-CNN is end-to-end trained and can generate high-quality segmentation results with edge guidance. Meanwhile, we also introduce a new benchmark data set named "Segmenting Objects in Day And night" (SODA) for comprehensive evaluations in thermal image semantic segmentation. SODA contains over 7168 manually annotated and synthetically generated thermal images with 20 semantic region labels and from a broad range of viewpoints and scene complexities. Extensive experiments on SODA demonstrate the effectiveness of the proposed EC-CNN against state-of-the-art methods.
The development of efficient red thermally activated delayed fluorescence (TADF) emitters with an emission wavelength beyond 600 nm remains a great challenge for organic light‐emitting diodes ...(OLEDs). Herein, two pairs of isomers are designed and synthesized by attaching electron‐donor 9,9‐diphenyl‐9,10‐dihydroacridine (DPAC) moiety to the different positions of two kinds of highly rigid planar acceptor cores (PDCN and PPDCN). Their TADF efficiencies and emission maxima (599–726 nm) are regulated by molecular isomer manipulation. Interestingly, the photoluminescence quantum yields (ΦPLs) of trans‐isomers T‐DA‐1 and T‐DA‐2 (78% and 89%) are remarkably higher than those of their corresponding cis‐isomers C‐DA‐1 and C‐DA‐2 (12% and 14%). Significantly increased ΦPL values can be explained by single crystal structures and theoretical simulation. As a result, a deep red TADF‐OLED based on T‐DA‐2 displays a maximum external quantum efficiency (EQE) of 26.26% at 640 nm. Notably, at a brightness of 100 cd m−2, the EQE value of T‐DA‐2‐based device still remains at an extremely high level of 23.95%, representing the highest value for reported red TADF‐OLEDs at the same brightness. These results provide a reasonable pathway to optimize optoelectronic properties and thereby construct efficient red TADF emitters through rational isomer engineering.
Two pairs of isomers with thermally activated delayed fluorescence and obviously different photoluminescence efficiency are developed via rational isomer engineering. A highly efficient red thermally activated delayed fluorescence organic light‐emitting diode with a maximum external quantum efficiency up to 26.26% at a peak wavelength of 640 nm and low roll‐off is achieved.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Photomultiplication (PM) type organic photodetectors (OPDs) based on electron tunneling injection are achieved with a specific structure of ITO/ZnO/PC
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BM:P3HT (100 : 5, wt/wt)/Au and can work well ...under forward and reverse bias. A rather low dark current density of the PM type OPDs is obtained due to the large electron injection barrier of 0.7 eV from the ITO electrode or 1.1 eV from the Au electrode, as well as the absence of continuous hole transport channels in the active layers. The external quantum efficiency (EQE) spectral shape of PM type OPDs can be easily adjusted by altering the bias polarity and active layer thickness, which can be well explained by the trapped hole distribution near the ITO and Au electrodes, respectively. The PM type OPDs with 400 nm active layers exhibit the maximum EQE of 3900% and 4900% under 5 V and −5 V bias, respectively. This work firstly achieves PM type OPDs with electron-only transport properties, which has great potential to well match with other organic electronic devices.
PM type OPDs are firstly achieved based on electron tunneling injection with electron-only transport properties.
Integrating multiple different yet complementary feature representations has been proved to be an effective way for boosting tracking performance. This paper investigates how to perform robust object ...tracking in challenging scenarios by adaptively incorporating information from grayscale and thermal videos, and proposes a novel collaborative algorithm for online tracking. In particular, an adaptive fusion scheme is proposed based on collaborative sparse representation in Bayesian filtering framework. We jointly optimize sparse codes and the reliable weights of different modalities in an online way. In addition, this paper contributes a comprehensive video benchmark, which includes 50 grayscale-thermal sequences and their ground truth annotations for tracking purpose. The videos are with high diversity and the annotations were finished by one single person to guarantee consistency. Extensive experiments against other state-of-the-art trackers with both grayscale and grayscale-thermal inputs demonstrate the effectiveness of the proposed tracking approach. Through analyzing quantitative results, we also provide basic insights and potential future research directions in grayscale-thermal tracking.
The design and synthesis of highly efficient deep red (DR) and near‐infrared (NIR) organic emitting materials with characteristic of thermally activated delayed fluorescence (TADF) still remains a ...great challenge. A strategy was developed to construct TADF organic solid films with strong DR or NIR emission feature. The triphenylamine (TPA) and quinoxaline‐6,7‐dicarbonitrile (QCN) were employed as electron donor (D) and acceptor (A), respectively, to synthesize a TADF compound, TPA‐QCN. The TPA‐QCN molecule with orange‐red emission in solution was employed as a dopant to prepare DR and NIR luminescent solid thin films. The high doped concentration and neat films exhibited efficient DR and NIR emissions, respectively. The highly efficient DR and NIR organic light‐emitting devices (OLEDs) were fabricated by regulating TPA‐QCN dopant concentration in the emitting layers.
TPA‐QCN with thermally activated delayed fluorescence was designed and synthesized. The pure crystal and thin film show intense deep red (DR) and NIR emissions, respectively. The supramolecular structure and intermolecular interactions are beneficial to the reduction of non‐radiative transitions and enhancement of emission in the solid state. Doped and neat films were used for high‐performance DR and NIR organic light‐emitting devices (OLEDs).
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Fabricating flexible pressure sensors with high sensitivity in a broad pressure range is still a challenge. Herein, a flexible pressure sensor with engineered microstructures on polydimethylsiloxane ...(PDMS) film is designed. The high performance of the sensor derives from its unique pyramid‐wall‐grid microstructure (PWGM). A square array of dome‐topped pyramids and crossed strengthening walls on the film forms a multiheight hierarchical microstructure. Two pieces of PWGM flexible PDMS film, stacked face‐to‐face, form a piezoresistive sensor endowed with ultrahigh sensitivity across a very broad pressure range. The sensitivity of the device is as high as 383 665.9 and 269 662.9 kPa−1 in the pressure ranges 0–1.6 and 1.6–6 kPa, respectively. In the higher pressure range of 6.1–11 kPa, the sensitivity is 48 689.1 kPa−1, and even in the very high pressure range of 11–56 kPa, it stays at 1266.8 kPa−1. The pressure sensor possesses excellent bending and torsional strain detection properties, is mechanically durable, and has potential applications in wearable biosensing for healthcare. In addition, 2 × 2 and 4 × 4 sensor arrays are prepared and characterized, suggesting the possibility of manufacturing a flexible tactile sensor.
A flexible piezoresistive pressure sensor with hierarchical microstructures on its interlocked polydimethylsiloxane sensing films is fabricated by using a specially designed silicon template with the unique pyramid‐wall grid microstructures of different height and a four‐step mold‐casting process. The sensor has ultrahigh sensitivity in a very wide pressure range, yielding better performance than most flexible pressure sensor in literature.
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The 2021 Mw 7.4 Maduo earthquake (eastern Tibetan Plateau), with a surface deformation zone that is characterized by multiple distinct surface rupture segments separated by segments with no surface ...ruptures, provides an excellent opportunity to constrain the strain threshold (minimum strain) for the formation of surface ruptures. Through sub‐pixel correlation of pre‐ and post‐event SPOT‐6/7 satellite images (pixel = 1.5 m), we derive surface displacement and shear‐strain fields of the Maduo earthquake. By quantifying the minimum shear strain along the surface rupture segments and the maximum shear strain along the segments with no surface ruptures, we estimate a rupture strain threshold, which ranges from 0.8% to 1.8% and appears to decrease with structural maturity of the causative fault. This threshold is generally consistent with a rupture strain limit (0.5%–1.5%) of intact rocks from laboratory measurements, and is higher than a commonly‐assumed strain threshold (0.5%) for inelastic deformation.
Plain Language Summary
During large earthquakes, two sides of the fault dislocate relative to each other and create a narrow surface deformation zone in between. Whether surface rupture can be produced depends on the strain, a unitless measurement of deformation, within the surface deformation zone. For natural earthquakes, the minimum strain that is needed to create surface rupture (the rupture strain threshold) has not yet been determined. Here we investigate such strain for the surface rupture of 2021 Mw 7.4 Maduo earthquake at the eastern Tibetan Plateau. By analyzing the Maduo coseismic surface strain field and its correlation with spatial extent of the coseismic surface rupture, we determine that the rupture strain threshold ranges from 0.8% to 1.8%, and it appears to decrease with structural maturity of the causative fault. This threshold is generally consistent with a rupture strain limit (0.5%–1.5%) of intact rocks from laboratory measurements, and is higher than a commonly‐assumed strain threshold (0.5%) for inelastic deformation. Our study, for the first time, provides a direct measurement of rupture strain threshold based on natural earthquake studies.
Key Points
We derive the 2021 Maduo coseismic surface displacement and strain fields through sub‐pixel correlation of SPOT‐6/7 optical images
The strain threshold for the formation of Maduo surface rupture is 0.8%–1.8%, and it appears to decrease with the causative fault maturity
This value is consistent with a laboratory‐derived rupture threshold 0.5%–1.5% and is higher than a commonly‐assumed inelastic threshold 0.5%
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Herein, a ternary boron‐oxygen‐nitrogen embedded polycyclic aromatic hydrocarbon with multiple resonance thermally activated delayed fluorescence (MR‐TADF), namely DBNO, is developed by adopting the ...para boron‐π‐boron and para oxygen‐π‐oxygen strategy. The designed molecule presents a vivid green emission with a high photoluminescence quantum yield (96 %) and an extremely narrow full width at half maximum (FWHM) of 19 nm/0.09 eV, which surpasses all previously reported green TADF emitters to date. In addition, the long molecular structure along the transition dipole moment direction endows it with a high horizontal emitting dipole ratio of 96 %. The organic light‐emitting diode (OLED) based on DBNO reveals a narrowband green emission with a peak at 504 nm and a FWHM of 24 nm/0.12 eV. Particularly, a significantly improved device performance is achieved by the TADF‐sensitization (hyperfluorescence) mechanism, presenting a FWHM of 27 nm and a maximum external quantum efficiency (EQE) of 37.1 %.
A ternary B−O−N embedded multiple resonance thermally activated delayed fluorescence emitter is developed based on the para B‐π‐B and O‐π‐O strategy. It exhibits a narrowband green emission with a full width at half maximum (FWHM) of 19 nm/0.09 eV and a preferential horizontal dipole ratio of 96 %. The corresponding organic light‐emitting diode (OLED) emits green light with a FWHM of 27 nm and a high external quantum efficiency (EQE) of 37.1 %.
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