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Transparent-to-dark photo- and electrochromic gels
摘要： Smart windows in which the transmittance can be controlled on demand are a promising solution for the reduction of energy use in buildings. Windows are often the most energy inefficient part of a building, and so controlling the transmittance has the potential to significantly improve heating costs. Whilst numerous approaches exist, many suitable materials are costly to manufacture and process and so new materials could have a significant impact. Here we describe a gel-based device which is both photo- and electrochromic. The gel matrix is formed by the self-assembly of a naphthalene diimide. The radical anion of the naphthalene diimide can be formed photo or electrochemically, and leads to a desirable transition from transparent to black. The speed of response, low potential needed to generate the radical anion, cyclability of the system, temperature stability and low cost mean these devices may be suitable for applications in smart windows.
关键词： Smart windows,Gel-based device,Naphthalene diimide,Electrochromic,Photochromic
更新于2025-09-23 15:21:01
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Hybrid Ligand Exchange of Cu(In,Ga)S <sub/>2</sub> Nanoparticles for Carbon Impurity Removal in Solution Processed Photovoltaics
摘要： The solution processing of Cu(In,Ga)(S,Se)2 photovoltaics from colloidal nanoparticles has long suffered from deleterious carbonaceous residues originating from long chain native ligands. This impurity carbon has been observed to hinder grain formation during selenization and leave a discrete residue layer between the absorber layer and the back contact. In this work, organic and inorganic ligand exchanges were investigated to remove tightly bound native oleylamine ligands from Cu(In,Ga)S2 nanoparticles, thereby removing the source of carbon contamination. However, incomplete ligand removal, poor colloidal stability, and/or selective metal etching was observed for these methods. As such, an exhaustive hybrid organic/inorganic ligand exchange was developed to bypass the limitations of individual methods. A combination of microwave-assisted solvothermal pyridine ligand stripping followed by inorganic capping with diammonium sulfide was developed and yielded greater than 98% removal of native ligands via a rapid process. Despite the aggressive ligand removal, the nanoparticle stoichiometry remained largely unaffected when making use of the hybrid ligand exchange. Furthermore, highly stable colloidal ink formulations using non-toxic dimethyl sulfoxide were developed, supporting stable nanoparticle mass concentrations exceeding 200 mg/mL. Scalable blade coating of the ligand exchanged nanoparticle inks yielded remarkably smooth and microcrack free films with RMS roughness less than 7 nm. Selenization of ligand exchanged nanoparticle films afforded substantially improved grain growth as compared to conventional non-ligand exchanged methods yielding an absolute improvement in device efficiency of 2.8%. Hybrid ligand exchange nanoparticle based devices reached total-area power conversion efficiencies of 12.0%, demonstrating the feasibility and promise of ligand exchanged colloidal nanoparticles for the solution processing of Cu(In,Ga)(S,Se)2 photovoltaics.
关键词： hybrid ligand exchange,blade coating,diammonium sulfide,carbon impurity removal,photovoltaics,grain growth,Cu(In,Ga)(S,Se)2,solution processing,ligand exchange,selenization,microwave-assisted solvothermal,colloidal nanoparticles,device efficiency
更新于2025-09-23 15:21:01
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Low color temperature, high color rendering index candlelight style white organic light-emitting devices with a fac-tris (mesityl-2-phenyl-1H-imidazole) iridium (III) blue emitting layer
摘要： Blue phosphorescent organic light-emitting devices based on fac-tris (mesityl-2-phenyl-1H-imidazole) iridium (III) (fac-Ir(mpim)3) doped in different host materials are fabricated. The device with a 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine host shows an excellent performance. Based on this blue emitting device, white organic light-emitting devices with high performance are achieved. The optimized device shows a color rendering index of 92 and a color temperature of 2572 K, which are comparable to the incandescent bulb. Besides, it also presents a high current ef?ciency of 23.1 cd A ?1 at brightness of 1000 cd m and a power ef?ciency of 15.8 lm W organic light-emitting device has the potential as a comfortable lighting source.
关键词： candlelight style white organic light-emitting device,CCT,CRI
更新于2025-09-23 15:21:01
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Effect of Interfacial Layers on the Device Lifetime of Perovskite Solar Cells
摘要： Organic–inorganic hybrid perovskites have excellent optical and electronic properties; exploitation of these traits has increased the power conversion efficiency of perovskite photovoltaics (PePVs) to 25.2%. However, perovskites are chemically unstable, and this deficit has critically impeded their commercialization. Device degradation occurs at the interfaces of PePVs with multiple degradation mechanisms: decomposition of organic cations in perovskites; generation of inorganic byproducts in perovskites; superoxide or trap sites at the interface of the charge-transport layer; excess charge carriers in perovskites; interfacial migration between perovskites and electrodes. This review considers the critical functions of the interfacial materials to overcome the various degradation at the interfaces of the PePVs. The working mechanisms stabilizing the interface of PePVs are categorized: passivation from atmosphere; inactivation of defect states; migration-blocking. Then, the outstanding interfacial layers made of organic materials (defect passivation, physical robustness, and chemical inactivation) and inorganic materials (chemically passivating metal oxide, physically passivating metal oxide, and low-temperature processed inorganic materials) are reviewed according to the stabilizing mechanisms. In addition, the influences of inorganic interconnecting layers in tandem PePVs are reviewed, with respect of various effects of interfacial buffer materials at the interface with perovskites.
关键词： device lifetime,interfacial layers,perovskite solar cells,stability,degradation mechanisms
更新于2025-09-23 15:21:01
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Unraveling the Complex Nanomorphology of Ternary Organic Solar Cells with Multimodal Analytical Transmission Electron Microscopy
摘要： Elucidating the complex materials distribution in the active layers of ternary organic solar cells is one of the greatest challenges in the field of organic photovoltaics. Knowledge of the nanomorphology is key to understanding photophysical processes (e.g. charge separation, adjustment of the recombination mechanism as well as suppression of the radiationless and energetic losses) and thus improving the device performance. Here, we demonstrate for the first time the successful discrimination and spatial mapping of the active layer components of a ternary organic solar cell using analytical transmission electron microscopy. The material distribution of all three organic components was successfully visualized by multimodal imaging using complementary electron energy loss signals. A complete picture of the morphological aspects could be gained by studying the lateral and cross-sectional morphology as well as the morphology evolution as a function of the mixing ratio of the polymers. Finally, a correlation between the morphology, photophysical processes and device performance of the ternary and the reference binary system was achieved, explaining the differences of the power conversion efficiency (PCE) between the two systems.
关键词： device performance,EFTEM,morphology,TEM,Ternary organic solar cells
更新于2025-09-23 15:21:01
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Optical coherence tomography: Translation from 3D-printed vascular models of the anterior cerebral circulation to the first human images of implanted surface modified flow diverters
摘要： Background: The new generation of flow diverters includes a surface modification with a synthetic biocompatible polymer, which makes the device more biocompatible and less thrombogenic. Optical coherence tomography (OCT) can be used to visualize perforators, stent wall apposition, and intra-stent thrombus. Unfortunately real world application of this technology has been limited because of the limited navigability of these devices in the intracranial vessels. In this report, we share our experience of using 3D-printed neurovascular anatomy models to simulate and test the navigability of a commercially available OCT system and to show the application of this device in a patient treated with the new generation of surface modified flow diverters. Material and methods: Navigability of OCT catheters was tested in vitro using four different 3D-printed silicone replicas of the intracranial anterior circulation, after the implantation of surface modified devices. Intermediate catheters were used in different tortuous anatomies and positions. After this assessment, we describe the OCT image analysis of a Pipeline Shield for treating an unruptured posterior communicating artery (PCOM) aneurysm. Results: Use of intermediate catheters in the 3D-printed replicas was associated with better navigation of the OCT catheters in favorable anatomies but did not help as much in unfavorable anatomies. OCT image analysis of a PCOM aneurysm treated with Pipeline Embolization Device Shield demonstrated areas of unsatisfactory apposition with no thrombus formation. Conclusions: OCT improves the understanding of the flow diversion technology. The development of less thrombogenic devices, like the Pipeline Flex with Shield Technology, reinforces the need for intraluminal imaging for neurovascular application.
关键词： Pipeline device,Aneurysm,optical coherence tomography
更新于2025-09-23 15:21:01
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Understanding degradation of organic light-emitting diodes from magnetic field effects
摘要： The impact of magnetic field effects on the electroluminescence of organic light-emitting diodes is commonly used to characterize exciton dynamics such as generation, annihilation, and performance degradation. However, interpreting these effects is challenging. Here, we show that magnetic field effects in organic light-emitting diodes can be understood in terms of the magnetic response of device characteristics derived from polaron-pair and triplet exciton quenching processes, such as triplet-polaron interactions and triplet-triplet annihilation. Device degradation shows a clear relationship with the amplitude of the magnetic field effects, enabling non-destructive measurement of the degradation. The results and proposed mechanism provide a better understanding of magnetic field effects on organic light-emitting diodes and device degradation phenomena.
关键词： magnetic field effects,device degradation,organic light-emitting diodes,triplet-polaron interactions,triplet-triplet annihilation,exciton dynamics
更新于2025-09-23 15:21:01
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Ideal alloys of two donor isomers with non-covalently conformational locking for ternary organic solar cells
摘要： Ternary organic solar cells (OSCs) based on the alloy model have great potential in maximizing the improvement of device performance due to the probability of simultaneously enhancing the photocurrent through morphology optimization and improving open circuit voltage (Voc) by energy level adjustment. However, rationally designing compatible materials and constructing an effective alloy remain difficult. In this manuscript, two donor isomers, BT-TO-ID and BT-OT-ID with non-covalently conformational locking of alkoxy groups at different position, were designed and synthesized to obtain an ‘‘ideal alloy’’. A linearly tunable Voc was observed between the Voc limitation of binary blends with the changes of the composition across the full range, indicating the behavior of an ideal alloy in the ternary blends. A face-on molecular packing and an appropriate phase separation was observed in the ternary blends due to the strong interactions between the two isomers, which facilitated charge transport and charge recombination suppression. Notable improvements of 76% and 29% in device performance were obtained for the ternary blends compared with BT-OT-ID based and BT-OT-ID based binary devices, respectively. Therefore, this work provided a probable molecular design strategy to guide the construction of an effective alloy in ternary OSCs.
关键词： Open circuit voltage,Non-covalently conformational locking,Alloy model,Device performance,Molecular packing,Phase separation,Ternary organic solar cells,Donor isomers
更新于2025-09-23 15:21:01
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Holographic Fabrication and Optical Property of Graded Photonic Super-Crystals with a Rectangular Unit Super-Cell
摘要： Recently developed graded photonic super-crystals show an enhanced light absorption and light extraction efficiency if they are integrated with a solar cell and an organic light emitting device, respectively. In this paper, we present the holographic fabrication of a graded photonic super-crystal with a rectangular unit super-cell. The spatial light modulator-based pixel-by-pixel phase engineering of the incident laser beam provides a high resolution phase pattern for interference lithography. This also provides a flexible design for the graded photonic super-crystals with a different ratio of length over the width of the rectangular unit super-cell. The light extraction efficiency is simulated for the organic light emitting device, where the cathode is patterned with the graded photonic super-crystal. The high extraction efficiency is maintained for different exposure thresholds during the interference lithography. The desired polarization effects are observed for certain exposure thresholds. The extraction efficiency reaches as high as 75% in the glass substrate.
关键词： spatial light modulator,holographic lithography,organic light emitting device,photonic crystals,graded photonic super-crystals,extraction efficiency
更新于2025-09-23 15:21:01
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Tiled Monolayer Films of 2D Molybdenum Disulphide Nanoflakes Assembled at Liquid/Liquid Interfaces
摘要： Thin films of MoS2 bilayer nanoflakes, which are predominantly a single flake thick and in edge-to-edge contact, have been produced via self-assembled tiling at the planar interface between two immiscible liquids. Films of several square centimeters extent can be produced with total covered area approaching 90 % and over 70 % of the film covered by single flakes without overlap. Films produced through liquid/liquid assembly are shown to produce a lower uncovered area fraction and more uniform thickness when compared with films of similar areal coverage produced by the “top-down” techniques of spin coating and spray coating. Statistical analysis of flake coverage data, measured by AFM, shows that liquid/liquid assembly produces a distinctly different variation in film thickness than conventional “top-down” deposition. This supports the hypothesis that the 2D confinement of liquid/liquid assembly produces more uniform films. Demonstrator field-effect transistors (FETs) manufactured from the films exhibit mobility and on/off current ratios of 0.73 cm2 V-1 s-1 and 105 respectively; comparable to FETs of similar layout and CVD-grown or mechanically cleaved single crystal MoS2 channel material. This work demonstrates the use of liquid/liquid interfaces as a useful tool for self-assembly of high performance thin film devices made from dispersions of 2D materials.
关键词： self-assembly,2D materials,coverage,device fabrication,thin films,Poisson distribution
更新于2025-09-23 15:21:01