Deep-blue thermally activated delayed fluorescence (TADF) emitters with National Television System Committee (NTSC) standard (0.14, 0.08) and narrowband emission have been one of the challenging ...issues for organic light-emitting diodes (OLEDs). In this work, a novel molecular design strategy, periphery cladding, was used to design and synthesize three deep-blue multi-resonance TADF emitters, N,N, 5,9-tetraphenyl-5,9-dihydro-5,9-diaza-13b-boranaphtho3,2,1-deanthracen-7-amine (PAB), 2,12-di-tert-butyl-5,9-bis(4-(tert-butyl)phenyl)-N,N-diphenyl-5,9-dihydro-5,9-diaza-13b-boranaphtho3,2,1-deanthracen-7-amine (2tPAB) and 2,12-di-tert-butyl-N,N,5,9-tetrakis(4-(tert-butyl)phenyl)-5,9-dihydro-5,9-diaza-13b-boranaphtho3,2,1-deanthracen-7-amine (3tPAB). By cladding large steric hindrance tert-butyl unit at periphery of multi-resonance emitter, the intermolecular interactions were suppressed, thus reducing aggregation-induced emission quenching and improving the PLQY of emitter. 3tPAB with full periphery cladding exhibited higher PLQY (74.7%). As a result, the device based on 3tPAB acquired the best performance by using 1,3-di(9H-carbazol-9-yl)benzene (mCP) with low polarity as host. The maximum external quantum efficiency (EQEmax), CIE coordinates, and full-width at half-maximum (FWHM) of 3tPAB-based device were 19.3%, (0.141, 0.076), and 26 nm, respectively. To our knowledge, this is the first report about narrowband TADF OLEDs with single host that EQEmax approaches 20% while CIE coordinates meet the NTSC blue-light standard.
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•Three deep-blue multi-resonance TADF emitters were designed and synthesized.•A useful strategy was demonstrated to improve the performance of multi-resonance TADF emitter.•EQEmax and CIE coordinates of the device based on 3tPAB exhibited 19.3% and (0.141, 0.076), respectively.
The electrophilic borylation site of borylation reaction can be selectively controlled by varying the steric hindrance and electron-donating ability of the substrate substituent. The device based on ...the synthesized compound exhibits EQE of 21.6% with FWHM of 28 nm and CIE coordinates of (0.135, 0.094). The work provides an effective way for the development of high-performance MR-TADF emitter.
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•The electrophilic borylation site of one-shot electrophilic C–H borylation reaction can be selectively controlled.•New compounds tDPAC-BN and tDMAC-BN exhibited high PLQYs, narrow FWHMs, and satisfactory TADF properties.•The device based on tDPAC-BN achieved EQE of 21.6% with FWHM of 28 nm and CIE coordinates of (0.135, 0.094).
Developing novel thermally activated delayed fluorescence (TADF) materials with a small full-width at half-maximum (FWHM) is very important for the fabrication of wide gamut and high-resolution displays of organic light-emitting diodes (OLEDs). In this work, we report two blue TADF emitters (tDPAC-BN and tDMAC-BN) with narrow FWHM based on a one-shot electrophilic C–H borylation reaction by selecting acridan-containing arylamine derivatives as the starting materials of borylation. The rigid skeleton structure significantly reduces vibrational motion, endowing tDPAC-BN and tDMAC-BN with high PLQYs (94.4% and 89.7%) and narrow FWHMs (19 nm and 26 nm in toluene). The electroluminescent devices employing tDPAC-BN and tDMAC-BN as emitters exhibit external quantum efficiency (EQE) of 21.6% and 22.3%, and CIE coordinates of (0.135, 0.094) and (0.116, 0.186), respectively. More importantly, we found the electrophilic borylation site of borylation reaction can be controlled by varying the steric hindrance effect and electron-donating ability of the substrate substituent. The different HOMO distribution originated from the differences in the substrate substituent accounts for different cyclization mode for tDPAC-BN and tDMAC-BN. Therefore, the work provides a useful strategy for broadening the range of high-performance TADF materials with narrow FWHM.
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The challenge of mitigating pollution stemming from industrial exhaust emissions is a pressing issue in both academia and industry. This study presents the successful synthesis of ...nitrogen-defect-enriched graphite carbon nitride (g-C3N4) using a two-step calcination technique. Furthermore, a g-C3N4-Au heterostructure was fabricated through the photo-deposited Au quantum dots (QDs). When subjected to visible light irradiation, this heterostructure exhibited robust nitric oxide (NO) photooxidation activity and stability. With its fluffy, porous structure and large surface area, the nitrogen-defect-enriched g-C3N4 provides more active sites for photooxidation processes. The ability of g-C3N4 to absorb visible light is enhanced by the local surface plasmon resonance (LSPR) effect of Au QDs. Additionally, the lifetime of photogenerated charge carriers is extended by the presence of N defects and Au, which effectively prevent photogenerated electron-hole pairs from recombining during the photooxidation process. Moreover, the oxidation pathway of NO was analyzed through In-situ Fourier transform infrared (FT-IR) spectroscopy and Density Functional Theory (DFT) calculation. Computational findings revealed that the introduction of Au QDs decreases the activation energy of the oxidation reaction, thereby facilitating its occurrence while diminishing the formation of intermediate products. As a result, NO is predominantly converted to nitrate (NO3−). This work unveils a novel approach to constructing semiconductor-cocatalyst heterostructures and elucidates their role in NO photooxidation.
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•Inorganic HAuCl4 doping combined organic NPB post-treatment strategy was proposed.•High PCE of 19.20% for Au@PEDOT:PSS/NPB PSCs is achieved on rigid substrate.•Flexible ...Au@PEDOT:PSS/NPB PSCs achieve 14.04% PCE with strong wrinkle resistance.•Improved hysteresis and stability of PSCs are realized via synchronous regulation.
The further improvements in optoelectronic properties, hydrophobicity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers, as well as regulation of defect states within devices are essential to promote the continued development of inverted p-i-n rigid and flexible planar perovskite solar cells (PSCs). However, the strong hygroscopicity, poor surface morphology, lower work function and coil configuration of pristine PEDOT:PSS films are detrimental to their own performance and growth dynamics process of perovskites, often resulting in sever energy losses and poor device performance. Herein, hydrogen tetrachloroaurate (III) hydrate (HAuCl4·3H2O) additive is combined with a conductive N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) buffer layer to boost device performance by systematically modulating PEDOT:PSS and perovskite film. Wherein, the redox reaction between PEDOT:PSS and HAuCl4 can cause phase segregation of PEDOT:PSS, improving the hydrophobicity, electrical conductivity, work function and surface morphology of the films. The reduced gold nanoparticles will produce localized surface plasmon resonance effects, thus enhancing the utilization of solar radiation by perovskite films. Furthermore, the suitable energy level alignment of NPB layer relative to perovskite and Au@PEDOT:PSS films will sufficiently exploit the dissociative excitons to facilitate effective hole transport, and the N atoms in NPB can also passivate defects at the interface by binding to uncoordinated Pb2+ ions, thereby reducing non-radiative open-circuit voltage loss and increasing short-circuit current density. A high power conversion efficiency (PCE) of 19.20% can be achieved for MA0.85FA0.15PbI3 based p-i-n PSCs with negligible hysteresis and enhanced stability of devices. Similarly, the corresponding flexible device achieves a PCE of 14.04% with improved crumpling durability throughout low temperature preparation conditions below 140 °C. Our work presents a facile method to prepare high-efficient inverted PSCs while achieving improved long-term device stability.
Thermal nonreciprocity typically stems from nonlinearity or spatiotemporal variation of parameters. However, constrained by the inherent temperature‐dependent properties and the law of mass ...conservation, previous works have been compelled to treat dynamic and steady‐state cases separately. Here, by establishing a unified thermal scattering theory, the creation of a convection‐based thermal metadevice which supports both dynamic and steady‐state nonreciprocal heat circulation is reported. The nontrivial dependence between the nonreciprocal resonance peaks and the dynamic parameters is observed and the unique nonreciprocal mechanism of multiple scattering is revealed at steady state. This mechanism enables thermal nonreciprocity in the initially quasi‐symmetric scattering matrix of the three‐port metadevice and has been experimentally validated with a significant isolation ratio of heat fluxes. The findings establish a framework for thermal nonreciprocity that can be smoothly modulated for dynamic and steady‐state heat signals, it may also offer insight into other heat‐transfer‐related problems or even other fields such as acoustics and mechanics.
Having developed a comprehensive thermal scattering theory that describes the nonreciprocal transmission properties of temperature field effectively, a metadevice that supports both dynamic and steady‐state nonreciprocal heat transfer is created. It uncovers the unique multiple‐scattering effect at steady state, which is anticipated to lead to intriguing applications in thermal energy utilization and thermal information processing.
Most T1 and T2 mapping take long acquisitions or needs specialized sequences not widely accessible on clinical scanners. An available solution is DESPOT1/T2 (Driven equilibrium single pulse ...observation of T1/T2). DESPOT1/T2 uses Spoiled gradient-echo (SPGR) and balanced Steady-State Free Precession (bSSFP) sequences, offering an accessible and reliable way for 3D accelerated T1/T2 mapping. However, bSSFP is prone to off-resonance artifacts, limiting the application of DESPOT2 in regions with high susceptibility contrasts, like the prostate. Our proposal, DESPO+, employs the full bSSFP and SPGR models with a dictionary-based method to reconstruct 3D T1/T2 maps in the prostate region without off-resonance banding.
DESPO+ modifies the bSSFP acquisition of the original variable flip angle DESPOT2. DESPO+ uses variable repetition and echo times, employing a dictionary-based method of the full bSSFP and SPGR models to reconstruct T1, T2, and Proton Density (PD) simultaneously. The proposed DESPO+ method underwent testing through simulations, T1/T2 phantoms, and on fourteen healthy subjects.
The results reveal a significant reduction in T2 map banding artifacts compared to the original DESPOT2 method. DESPO+ approach reduced T2 errors by up to seven times compared to DESPOT2 in simulations and phantom experiments. We also synthesized in-vivo T1-weighted/T2-weighted images from the acquired maps using a spin-echo model to verify the map's quality when lacking a reference. For in-vivo imaging, the synthesized images closely resemble those from the clinical MRI protocol, reducing scan time by around 50% compared to traditional spin-echo T1-weighted/T2-weighted acquisitions.
DESPO+ provides an off-resonance insensitive and clinically available solution, enabling high-resolution 3D T1/T2 mapping and synthesized T1-weighted/T2-weighted images for the entire prostate, all achieved within a short scan time of 3.6 min, similar to DESPOT1/T2.
We solve the problem of determination of the stress state of an infinitely long cylinder of an arbitrary cross section under the conditions of longitudinal shear vibrations in the presence of ...interaction between through defects (a crack and a thin rigid inclusion
)
. We use a method that enables one to satisfy the conditions imposed on the surfaces of defects and the boundary conditions of time-harmonic loading. We propose approximate formulas for the evaluation of stress intensity factors with the help of which we investigate the influence of the geometric parameters of cross section of the cylinder on the values of resonance frequencies.
Purpose
The sensitivity of pseudo‐continuous arterial spin labeling (PCASL) to off‐resonance effects (ΔB0) is a major limitation at ultra‐high field (≥7T). The aim of this study was to assess the ...effectiveness of different PCASL ΔB0 compensation methods at 7T and measure the labeling efficiency with off‐resonance correction.
Theory and Methods
Phase offset errors induced by ΔB0 at the feeding arteries can be compensated by adding an extra radiofrequency (RF) phase increment and transverse gradient blips into the PCASL RF pulse train. The effectiveness of an average field correction (AVGcor), a vessel‐specific field‐map‐based correction (FMcor) and a vessel‐specific prescan‐based correction (PScor) were compared at 7T. After correction, the PCASL labeling efficiency was directly measured in feeding arteries downstream from the labeling location.
Results
The perfusion signal was more uniform throughout the brain after off‐resonance correction. Whole‐brain average perfusion signal increased by a factor of 2.4, 2.5, and 2.1, respectively, with AVGcor, FMcor and PScor compared to acquisitions without correction. With off‐resonance correction, the maximum labeling efficiency was ~0.68 at mean B1 (B1mean) of 0.70 µT when using a mean gradient (Gmean) of 0.25 mT/m.
Conclusion
Either a prescan or a field map can be used to correct for off‐resonance effects and retrieve a good brain perfusion signal at 7T. Although the three methods performed well in this study, FMcor may be better suited for patient studies because it accounted for vessel‐specific ΔB0 variations. Further improvements in image quality will be possible by optimizing the labeling efficiency with advanced hardware and software while satisfying specific absorption rate constraints.
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