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A novel orange–red emitting phosphor Sr2LuTaO6:Sm3+ for WLEDs
摘要： A novel double perovskite tantalite orange–red light emitting Sr2LuTaO6:Sm3+ phosphor was synthesized by the solid state reaction. The phase, crystal structure, photoluminescence properties, thermal stability and decay curves were studied. The X-ray diffraction patterns indicated that the phosphor has a pure phase of cubic phase structure. Excited by near-ultraviolet light at 407 nm, the sample exhibited three sharp emission peaks at 564 nm, 600 nm, 645 nm corresponding to the 4G5/2 → 6HJ (J = 5/2, 7/2 and 9/2) transitions, respectively. The optimum doping concentration of Sm3+ ions was determined to be 5 mol% and the concentration quenching process comes from the energy transfer among nearest-neighbor ions. The as-prepared phosphors showed excellent thermal stability, the integral intensity at 423 K is about 91.10% of the initial intensity. The CIE chromaticity coordinates of Sr2LuTaO6:Sm3+ phosphors located in orange–red region. The results suggest that Sr2LuTaO6:Sm3+ phosphors have great potential application in white light-emitting diodes.
关键词： luminescence,thermal stability,white light-emitting diodes,Sr2LuTaO6:Sm3+,phosphor
更新于2025-11-14 15:13:28
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Prototyping of Superhydrophobic Surfaces from Structure-Tunable Micropillar Arrays Using Visible Light Photocuring
摘要： A new approach is reported to fabricate micropillar arrays on transparent surfaces by employing the light-induced self-writing technique. A periodic array of microscale optical beams is transmitted through a thin film of photo-crosslinking acrylate resin. Each beam undergoes self-lensing associated to photopolymerization-induced changes in the refractive index of the medium, which counters the beam’s natural tendency to diverge over space. As a result, a microscale pillar grows along each beam’s propagation path. Concurrent, parallel self-writing of micropillars leads to the prototyping of micropillar-based arrays, with the capability to precisely vary the pillar diameter and inter-spacing. The arrays are spray coated with a thin layer of polytetrafluoroethylene (PTFE) nanoparticles to create large-area superhydrophobic surfaces with water contact angles greater than 150° and low contact angle hysteresis. High transparency is achieved over the entire range of micropillar arrays explored. The arrays are also mechanically durable and robust against abrasion. This is a scalable, straightforward approach toward structure-tunable micropillar arrays for functional surfaces and anti-wetting applications.
关键词： light-induced self-writing,re-entrant,micropillars,hydrophobicity,nanoparticles
更新于2025-10-24 16:36:04
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Ultraviolet patterns of flowers revealed in polymer replica – caused by surface architecture
摘要： Angiosperms and their pollinators are adapted in a close co-evolution. For both the plants and pollinators, the functioning of the visual signaling system is highly relevant for survival. As the frequency range of visual perception in many insects extends into the ultraviolet (UV) region, UV-patterns of plants play an important role in the flower–pollinator interaction. It is well known that many flowers contain UV-absorbing pigments in their petal cells, which are localized in vacuoles. However, the contribution of the petal surface microarchitecture to UV-reflection remains uncertain. The correlation between the surface structure and its reflective properties is also relevant for biomimetic applications, for example, in the field of photovoltaics. Based on previous work, we selected three model species with distinct UV-patterns to explore the possible contribution of the surface architecture to the UV-signaling. Using a replication technique, we transferred the petal surface structure onto a transparent polymer. Upon illumination with UV-light, we observed structural-based patterns in the replicas that were surprisingly comparable to those of the original petals. For the first time, this experiment has shown that the parameters of the surface structure lead to an enhancement in the amount of absorbed UV-radiation. Spectrophotometric measurements revealed up to 50% less reflection in the UV-absorbing regions than in the UV-reflecting areas. A comparative characterization of the micromorphology of the UV-reflecting and UV-absorbing areas showed that, in principle, a hierarchical surface structure results in more absorption. Therefore, the results of our experiments demonstrate the structural-based amplification of UV-reflection and provide a starting point for the design of bioinspired antireflective and respectively strongly absorbing surfaces.
关键词： hierarchical structures,biomimetics,light absorption,light harvesting,light reflection
更新于2025-10-22 19:40:53
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI, USA (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Mitigating optical losses in crystalline silicon thin-film solar cells on glass
摘要： Liquid phase crystallized silicon thin-film solar cells on glass provide efficiencies up to 14.2 %. While open-circuit voltage and fill factor are already comparable to wafer-based devices, short-circuit current density is reduced due to incomplete light absorption. This paper analyzes the losses of current device designs in experiment and one-dimensional simulations, revealing the low absorber thickness of 15-20 μm as well as the planar glass-silicon interface as the main cause of non-absorption. Interface textures, in particular a sinusoidal texture and a smooth anti-reflective three-dimensional (SMART) texture, are discussed concerning their potential to mitigate these losses, allowing to reduce losses at the glass-silicon interface by at least 40% relative. Taking the electronic interface quality into account, the SMART texture is identified as the most promising texture for light management in liquid phase crystallized silicon thin-film solar cells on glass.
关键词： light management,thin-film solar cells,absorption enhancement,silicon
更新于2025-10-22 19:40:53
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Maze-Like Halide Perovskite Films for Efficient Electron Transport Layer-Free Perovskite Solar Cells
摘要： Perovskite solar cells (PSCs) without an electron transport layer (ETL) exhibit fascinating advantages such as simplified configuration, low cost, and facile fabrication process. However, the performance of ETL-free PSCs has been hampered by severe charge carrier recombination induced either by current leakage (insufficient perovskite film coverage) or inferior charge extraction. Herein, an additive-assisted morphological engineering strategy is used to construct an intriguing bilayer perovskite film featuring a dense bottom layer and a maze-like top layer. Such maze-like perovskite films enable the construction of ETL-free PSCs with a PCE of 18.5% and negligible hysteresis, which can be attributed to the higher crystallinity and superior light-harvesting capability of the resultant perovskite film, as well as facilitated hole extraction at the hole transport layer (HTL)/perovskite interface. This work provides a simple approach to modify the perovskite film morphology and demonstrates the correlation between facilitated charge-carrier extraction and high-performance ETL-free perovskite photovoltaics.
关键词： light harvesting,morphological engineering,additives,perovskite solar cells,charge extraction
更新于2025-10-22 19:40:53
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Hole Blocking Layer-Free Perovskite Solar Cells with High Efficiencies and Stabilities by Integrating Subwavelength-Sized Plasmonic Alloy Nanoparticles
摘要： Perovskite solar cells hold great promise as prospective alternatives of renewable power sources. Recently hole blocking layer-free perovskite solar cells, getting rid of complex and high-temperature fabrication processes, have engaged in innovative designs of photovoltaic devices. However, the elimination of the hole blocking layer constrains the energy conversion efficiencies of perovskite solar cells, and severely degrades the stabilities. In this paper a simple approach (without energy-consuming and time-consuming procedures) for the fabrication of hole blocking layer-free perovskite solar cells has been demonstrated by an integration of copper-silver alloy nanoparticles, which are synthesized by wet chemical method with controllable diameters and elemental compositions. The rear-side integration of the subwavelength-sized silver-copper alloy particles (200 nm diameter), through a spraying/drying method, realizes a pronounced absorption enhancement of the perovskite layer by effectively light scattering in a broadband wavelength range, and achieves a series resistance decrease of the solar cell due to high electrical conductivities of the alloy particles. The particle integration achieves the highest efficiency of 18.89% due to the significant improvement in both optical and electrical properties of solar cells, making this device one of the highest-performing blocking layer-free perovskite solar cells and plasmonic perovskite solar cells. Moreover, the copper-based nanoparticles prevent the perovskite from diffusing into metal back electrodes. Because the diffusion can lead to a severe corrosion of the Au electrode and thus an efficiency degradation, the alloy nanoparticle integration between the perovskite and the electrode results in 80% and 200% improvements in the long-term stability and the photostability of solar cells, respectively. Through the proposed simple and effective fabrication process, our results open up new opportunities in the manufacturability of perovskite solar cells.
关键词： light scattering,Perovskite solar cells,plasmonic,subwavelength-sized,alloy,hole blocking layer,stability
更新于2025-10-22 19:40:53
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Microwave-assisted synthesis of FexZn1?xO nanoparticles for use in MEH-PPV nanocomposites and their application in polymer light-emitting diodes
摘要： A one-step microwave-assisted polyol method was used to fabricate FexZn1?xO (x = 0.01, 0.05, 0.10) nanoparticles. Zinc acetate dihydrate, iron (III) acetylacetonate, oleic acid and diethylene glycol were placed in a Teflon-lined reaction vessel. The reaction mixture was heated up to 250 °C for 15 min in a microwave reactor. The surface modification with oleic acid prevented agglomeration of the nanoparticles. The X-ray diffraction analysis revealed characteristics wurtzite hexagonal structure of ZnO and successful incorporation of the Fe dopant into the host crystal lattice. Doping of ZnO by Fe led to bandgap modification as estimated by Tauc plot. The as-prepared nanopowders were dispersed in toluene and mixed with a poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) polymer to make stable homogenous dispersions. Then, the FexZn1?xO/MEH-PPV nanocomposite thin films were prepared by spin coating and used as thin active layers in polymer light-emitting diodes. The thickness of deposited FexZn1?xO/MEH-PPV film was ca. 30 nm and that of reference neat MEH-PPV film was ca. 25 nm. The electroluminescent spectroscopy study showed that direct blending of MEH-PPV with Fe-doped ZnO nanoparticles is a simple and effective approach to significantly increase the luminance intensity of the diode in comparison to the diode fabricated by neat MEH-PPV.
关键词： Polymer light-emitting diodes,FexZn1?xO nanoparticles,Microwave-assisted synthesis,MEH-PPV nanocomposites
更新于2025-10-22 19:40:53
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Enhancing light absorption by colloidal metal chalcogenide quantum dots <i>via</i> chalcogenol(ate) surface ligands
摘要： Chemical species at the surface (ligands) of colloidal inorganic semiconductor nanocrystals (QDs) markedly impact the optoelectronic properties of the resulting systems. Here, post-synthesis surface chemistry modification of colloidal metal chalcogenide QDs is demonstrated to induce both broadband absorption enhancement and band gap reduction. A comprehensive library of chalcogenol(ate) ligands is exploited to infer the role of surface chemistry on the QD optical absorption: the ligand chalcogenol(ate) binding group mainly determines the narrowing of the optical band gap, which is attributed to the np occupied orbital contribution to the valence band edge, and mediates the absorption enhancement, which is related to the π-conjugation of the ligand pendant moiety, with further contribution from electron donor substituents. These findings point to a description of colloidal QDs that may conceive ligands as part of the overall QD electronic structure, beyond models derived from analogies with core/shell heterostructures, which consider ligands as mere perturbation to the core properties. The enhanced light absorption achieved via surface chemistry modification may be exploited for QD-based applications in which an efficient light-harvesting initiates charge carrier separation or redox processes.
关键词： colloidal metal chalcogenide quantum dots,light absorption,optoelectronic properties,surface ligands,band gap reduction
更新于2025-10-22 19:40:53
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Light management in crystalline silicon thin-film solar cells with imprint-textured glass superstrate
摘要： The implementation of light management textures in thin-film solar cells often simultaneously causes an undesired deterioration of electronic performance. Here, we introduce a simple yet effective technique for improved light management in liquid phase crystallized silicon thin-film solar cells on glass. By imprinting pyramidal textures on the sun-facing side of the glass superstrate, absorber and functional layers of the device remain unaffected while light in-coupling is significantly increased. An increase of short-circuit current density by 2.5 mA cm2 was observed by texturing the glass in this way, corresponding to an enhanced power conversion efficiency from 12.9% to 13.8%. Optical simulations allow to attribute the increase in equal shares to an anti-reflective effect at the air-glass interface as well as light scattering and multiple passes through the glass. The technology allows for independent optimization of optical performance without compromising on electronic material issues and is therefore useable for any other solar cell technology using a glass superstrate.
关键词： Light management,Nano-imprint lithography,Liquid phase crystallization,Thin-film solar cells,Silicon
更新于2025-10-22 19:40:53
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Single crystal structure and electroluminescence efficiency of blue fluorescence OLED emitters using triple core chromophores
摘要： The relationship between the single crystal structure of materials and the EL performance of doped OLED devices was investigated. The 1,6-bis-(10-[1,1′;3′,1″]terphenyl-5′-yl-anthracen-9- yl)-pyrene (1,6 DAP-TP) has a dihedral angle (α) of 78.4 ° and a dihedral angle (β) of 81.2 °, a relatively more twisted single crystal structure compared to that of 6,12-bis-(10- [1,1′;3′,1″]terphenyl-5′-yl-anthracen-9-yl)-chrysene (DAC-TP). Such a highly twisted molecular structure can improve the electroluminescence (EL) efficiency of a material because it can inhibit rotational and vibrational motions. Also, since the doped state and single crystal structure imply, respectively, a diluted state and a molecular state, the EL efficiency of the doped OLED device is related to single crystal structure. In a 4% doped OLED device, 1,6 DAP-TP and DAC- TP showed CE of 2.10 cd A-1 and 0.93 cd A-1, respectively. With its relatively more twisted single crystal structure, 1,6 DAP-TP showed higher CE in a doped OLED device than DAC-TP. Both compounds had ultra-deep blue emission y values of 0.06 or less for the color coordinates, which satisfy high density television display requirements (y value less than 0.08).
关键词： Organic light-emitting diode,single crystal,fluorescence,dopant,blue
更新于2025-10-22 19:40:53