Salient Features in the Preparation of Promethium-147 Activated Zinc Sulphide Phosphor Light Sources

Activation of zinc sulphide phosphor with beta radiation of ¹⁴⁷Pm will provide self-sustaining light sources and are widely used as nocturnal illumination devices. Use of ¹⁴⁷Pm as energy source is most promising since it forms non-volatile salts. By virtue of this property, it has been precipitated as hydroxide from its aqueous solution for in situ deposition on zinc sulphide phosphor. In this paper, the details of various reaction parameters such as the rate of deposition of ¹⁴⁷Pm(OH)₃ on ZnS, duration of shaking, specific activity of phosphor and effect of fatty acid (additive) concentration versus luminosity are illustrated with experimental evidence so as to obtain, under optimum conditions, an overall luminosity of 1000 micro lamberts (lm).     

聚光光伏系统散热研究进展

对聚光光伏系统的发展过程进行了回顾。根据电池和聚光系统分类介绍了相匹配的散热冷却方式。电池组合方式简单、聚光倍数低的系统,使用传统风冷、水冷的被动散热即可满足要求;电池组合方式复杂、聚光倍数高的系统,常利用液浸冷却、射流冲击、通道冷却或多方法组合的新型冷却方式。指出在控制成本的前提下,选择系统可靠性高、结构简单的换热方式是聚光光伏电池从研究走向商用的关键;总结了国内外相关学者对各种聚光光伏电池散热系统的研究,介绍了各种技术的优越性和不足之处。     

A novel Cr3+-activated far-red titanate phosphor: synthesis,luminescence enhancement and application prospect

Plant factory, a new agricultural planting technology, has emerged and rapidly grown in recent years, with phosphor conversion light emitting diodes (pc-LEDs) considered as the first choice of source light for the plant factory. In this study, a new type of Cr³⁺-activated Li₂MgTi₃O₈ phosphor (LMT: Cr³⁺) was synthesized by high temperature solid state method. X-Ray diffraction patterns showed that there was no detectable impurity in these samples. The photoluminescence spectra revealed that this phosphor can emit far-red light with the peak at 740 nm excited by ultraviolet and blue light, overlapped well with the P_FR. After introducing Zn²⁺ ions (LMT: Cr³⁺, Zn²⁺), the luminescence intensity increases by 46% mainly due to the increase of lattice distortion, and internal quantum yield was improved from 25.4% to 41.3% under 365 nm excitation. Finally, the pc-LED devices, consisting of 470 nm chip coated with the optimal phosphor, exhibited good luminescence and overlapping with P_FR. These results indicate that the LMT: Cr³⁺, Zn²⁺ phosphor has the potential application in modern agriculture.     

Photoluminescence property of a novel inorganic-organic red emitting phosphor based on Mg/Al/Eu layered double hydroxide

A novel inorganic-organic red light emitting phosphor was synthesized by intercalating a sensitizer anion, terephthalate into Mg/Al/Eu layered double hydroxides through an ion exchange method. The basal spacing is 13.9 Å, indicating that a vertical arrangement of terephthalate anions within the gallery is adopted. This material displays much enhanced red luminescence from Eu³⁺ ions, suggesting that there is an efficient energy transfer from the excited state of the intercalated terephthalate anions to Eu³⁺ centres in the host layers. The optimal doping concentration of Eu³⁺ is 10 mol %.     

Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer

A SrLiAl₃N₄:Eu²⁺ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f⁶5d→4f⁷ transition bands are thought to result from the existence of Eu²⁺ at two different Sr²⁺ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm^?1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu^2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y₃Al₅O₁₂:Ce³⁺ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K.     

Organic Photovoltaic Cells with Improved Performance Using Bathophenanthroline as a Buffer Layer

The role of bathophenanthroline (Bphen) as a buffer layer inserted between fullerene (C₆₀) and Ag cathode in organic photovoltaic (OPV) cell was discussed. By introducing Bphen as a buffer layer with thicknes from 0 to 2.5 nm, the power conversion efficiency of the OPV cell based on copper phthalocyanine (CuPc) and C₆₀ was increased from 0.87% to 2.25% under AM 1.5 solar illumination at an intensity of 100 mW/cm², which was higher than that of bathocuproine used as a buffer layer. The photocurrent-voltage characteristics showed that Bphen effectively improves electron transport through C₆₀ layer into Ag electrode and leads to balance charge carrier transport capability. The influence of Bphen thickness on OPV cells was also investigated. Furthermore, the absorption spectrum shows that an additional Bphen layer enhances the light harvest capability of CuPc/C₆₀.     

Efficient charge collection with sol–gel derived colloidal ZnO thin film in photovoltaic devices

Polymer bulk heterojunction photovoltaic cell was fabricated by inserting a sol–gel derived ZnO thin film as an electron collecting layer between the fluorine-doped SnO₂ (FTO) and polymer-fullerene blend active layer. We demonstrated that the performance of device depends on sol concentration and the sol–gel process. Ammonia treatment on the ZnO film improved the efficiency of the device due to the effective removal of acetate group on the film. The short circuit current density was further increased by fine-tuning the thickness of ZnO film. The photovoltaic cell with this structure (FTO/ZnO film/polymer-fullerene blend/Au) produced a power conversion efficiency of 2.01% under simulated AM1.5G illumination of 100 mW/cm².     

A novel orange phosphor of Eu-activated calcium chlorosilicate for white light-emitting diodes

Novel orange phosphor of Eu²⁺-activated calcium chlorosilicate was synthesized at 1273 K by conventional solid-state reactions under reductive atmosphere and investigated by means of photoluminescence excitation, diffuse reflectance and emission spectroscopies. These results show that this phosphor can be efficiently excited by the incident light of 300-450 nm, well matched with the emission band of 395 nm-emitting InGaN chip, and emits an intense orange light peaking at 585 nm. By combining this phosphor with a 395 nm-emitting InGaN chip, an intense orange light-emitting diode (LED) was fabricated. Under 20 mA forward-bias current, its CIE chromaticity coordinates are (0.486, 0.446). The dependence of as-fabricated orange LED on forward-bias current indicates that it shows excellent chromaticity stability and luminance saturation. These results show that this Eu²⁺-activated calcium chlorosilicate is a promising orange-emitting phosphor for near-ultraviolet (UV) InGaN-based white LED.     

The radioisotopic battery based on radio-voltaic effect

The radio-voltaic effect is investigated to be applied radioisotopic batteries in this work. The collection rates of the electron-hole pairs are 94 percent for the alpha particles emitted by²³⁹Pu source and 65 percent for the beta particles emitted by⁹⁰Sr-⁹⁰Y source. The maximum energy conversion efficiency got by the silicon element is about 16%. A prototype radioisotopic battery with¹⁴⁷Pm beta sources is constructed. Its maximum short-circuit current and off voltage are about 2 A and 190 mV respectively. The experimental data suggest that the life of the prototype battery may be more than three years.     

Photoelectrical properties of Langmuir–Blodgett films of poly(methyl phenylsilane)s

Langmuir–Blodgett (LB) films were prepared from poly(methylphenylsilane) bearing electron acceptor π-conjugated substituents. The small limiting area (0.078 nm²) per one repeating unit of polysilane (PSi) in monomolecular film and the large thickness of the film (6 nm) suggest that the polymer chains are not fully spread on water surface. The electrical and photoelectrical properties of Al/LB film/Au sandwich cells containing various numbers of the polysilane layers were studied. Holes were transported from the Al electrode through the LB film to the Au electrode when the light was absorbed by the polysilane. The highest photovoltaic effect occurred in the first monolayer of polysilane at the Al contact. The cell resistivity and the photovoltage were decreased by parallel conductance of defects in the films consisting of small numbers of PSi layers.     

A novel blue-emitting phosphor LiSrPO4:Eu for white LEDs

A novel blue-emitting phosphor, LiSrPO₄:Eu²⁺, was prepared by the solid-state reaction and X-ray powder diffraction (XRD) analysis confirmed the formation of LiSrPO₄:Eu²⁺. Photoluminescence (PL) results showed that the phosphor can be efficiently excited by UV-visible light from 250 to 440 nm, and exhibited bright blue emission. The effects of the doped-Eu²⁺ concentration in LiSrPO₄:Eu²⁺ on the PL were investigated in detail. The results showed that the relative PL intensity increases with Eu²⁺-concentration increasing until a maximum intensity is reached, and then it decreases due to concentration quenching and a red-shift appears, which are explained satisfactorily with the luminescent theory. Upon excited with 396 nm light, the present synthesized phosphor has higher emission intensity than that from the commercial blue phosphor, BaMgAl₁₀O₁₇:Eu²⁺. Bright blue light-emitting diodes were fabricated by the combination of the synthesized LiSrPO₄:Eu²⁺ with ∼397 nm emitting InGaN-based chips.     

Development of diode junction nuclear battery using 63Ni

The diode junction nuclear battery is a long-lived, high-energy-density, but low electrical current power source with many specialized applications. In this type of battery, nuclear radiation is directly converted to electric power. A model is described and used to design the device configuration. Details of fabrication and testing of a planar geometry battery with ⁶³Ni radiation source are described. The electron beam induced current (EBIC) measurement technique and CASINO Monte Carlo simulation code were employed to analyze the device performance. Finally, an improved design with 3-dimensional surface microstructures that will provide improved performance is presented.     

Thermally stable deep-red emitting Sr2GdTaO6:Mn4+ double perovskites for indoor plant growth LEDs

Indoor artificial cultivation of plants is a novel technology applied to agriculture, and the emission band of luminescent materials can be matched with the needs of plants to promote plant growth. In this contribution, novel Mn⁴⁺ doped Sr₂GdTaO₆ (SGTO) deep-red phosphor was synthesized. This material was characterized, in detail, by X-ray diffractometer, SEM, and photoluminescence emission spectra. Sr₂GdTaO₆:Mn⁴⁺ (SGTO:Mn⁴⁺) can be effectively excited by near-ultraviolet (NUV) light, and the broadband emission of deep-red light matches the absorption band of plant phytochromes P_R and P_FR. The optimum doping concentration of Mn⁴⁺ in SGTO was 0.6 mol%, and the concentration quenching mechanism was attributed to dipole-quadrupole (d-q) electric interaction. The photoluminescence emission intensity of SGTO:0.006Mn⁴⁺ at 423 K is 80.6% of that at room temperature and the internal quantum efficiency of SGTO:0.006Mn⁴⁺ is 36.09%. Finally, the performance of the commercial 440 nm light-emitting diode chip/SGTO:0.006Mn⁴⁺ encapsulated light-emitting diode device was stable and can meet the needs of plants for the blue and red light. The results showed that SGTO:0.006Mn⁴⁺ deep-red phosphor is expected to be a phosphor suitable for indoor plant growth lighting.     

Photon trapping by the internal Bragg reflection of colloidal crystals

Fluorescence light emitted from photoexcited rhodamine 6G (R6G) doped in colloidal crystals of exhaustively deionized colloidal silica suspension is partially trapped within a crystal cage. This photon trapping is caused by Bragg reflection in crystal lattices. The photon trapping efficiencies were quantitatively examined as a function of the thickness of measurement cell. The efficiency increased from about 40 to 60% as the cell thickness increased from 1 to 10 mm for an R6G concentration of 5×10⁻⁶ mol/L. This result is attributed to an increase in the number of crystal layers perpendicular to the observation direction; these are formed in the cell with a large optical path length. On the other hand, the trapping efficiencies were constant irrespective of the angle between the incident and observed light of the cylindrical cells. The constant efficiencies are attributed to the fact that the heterogeneous crystal layers around the inner cell wall have the same thickness.     

Fast,Direct, Low‐Cost Route to Scalable,Conductive, and Multipurpose Poly(3,4‐ethylenedixoythiophene)‐Coated Plastic Electrodes

Poly(3,4‐ethylenedioxythiophene) (PEDOT) films are deposited, using an electroless method, onto flexible plastic poly(ethylene terephthalate) (PET) substrates of approximately 20×6 cm². The sheet resistance of a PEDOT–PET film is approximately 600 Ω per square, and the nanoscale conductivity is 0.103 S cm^?1. A plastic electrochromic PEDOT–Prussian blue device is constructed. The device undergoes a color change of pale blue to deep violet–blue reversibly over 1000 cycles, thus demonstrating its use as a light‐modulating smart window. The PEDOT–PET film is also used in a quantum dot solar cell, and the resulting photoelectrochemical performance and work function indicate that it is also promising for photovoltaic cells. The high homogeneity of the PEDOT deposit on PET, the optimal balance between conductivity and optical transparency, and the demonstration of its use in an electro‐optical device and a solar cell, offer the opportunity to use this electrode material in a variety of low‐cost optoelectronic devices.     

Comparison of degradation effects induced by gamma radiation and electron beam radiation in two cable jacketing materials

The radiation degradation behavior of commercial low density polyethylene (LDPE) and ethylene–vinylacetate (EVA) cable materials has been investigated. The changes of mechanical properties, thermooxidative stability and density exhibit different radiation stability towards ⁶⁰Co-gamma radiation and 160 keV electron beam radiation. This difference reflects much higher penetration of the gamma radiation through the polymeric material as a function of sample thickness. These results are discussed with respect to the role of beta radiation during design basis events in a nuclear power plants. In case when total accidental design basis event (DBE) dose (involving about 80% soft beta radiation) is simulated by ⁶⁰Co-gamma radiation the conservatism is reached.     

Eu3+掺杂双钙钛矿Sr2CaMoO6橙红色荧光粉的结构特征及其发光性能

采用EDTA-柠檬酸联合配位法制备一系列组成的(Sr1-xEux)2CaMoO6橙红色荧光粉。通过X射线衍射、拉曼光谱、扫描电镜及荧光光谱研究不同Eu3+离子掺杂浓度下Sr2CaMoO6∶Eu3+荧光粉的晶体结构、掺杂位置、形貌及其光致发光性能。Rietveld全谱拟合结果表明:掺杂后样品为(Ca/Mo)O6八面体少量倾斜的空间群为P21/n的正交双钙钛矿结构,随着Eu3+离子共掺杂浓度的增加,样品的晶胞体积减小;Eu3+离子取代八面体间隙的Sr2+位置致使双钙钛矿的T2g(1)拉曼振动模发生蓝移;在近紫外区宽而强电荷迁移带和蓝光激发下,该荧光粉分别发射以Eu3+离子5D0-7F1磁偶极跃迁为主的橙光和以5D0-7F2电偶极跃迁为主的红光,组成为(Sr0.98Eu0.02)2CaMoO6的荧光粉具有最强的橙红光发射强度,是一种潜在的适用于近紫外LED芯片的光转换红光材料。     

Bilayer inverse opal TiO2 electrodes for dye-sensitized solar cells via post-treatment

We investigated the formation of bilayer inverse opal TiO(2) (io-TiO(2)) structures via post-treatment with a TiO(2) precursor solution and characterized the photovoltaic performances of the resulting electrodes for use in dye-sensitized solar cells. The post-treatment of TiO(2) inverse opals in a precursor solution grew rutile TiO(2) nanoparticles on anatase crystalline phase io-TiO(2) surfaces, resulting in anatase/rutile bilayer structures. We achieved a maximum photovoltaic conversion efficiency of 4.6% using a 25 μm thick electrode formed with the post-treated io-TiO(2) under simulated AM 1.5 light. This efficiency represents a 183% improvement over the non-post-treated io-TiO(2) electrodes. The shell thickness was controlled by the post-treatment time. The effects of shell thickness on photovoltaic performance were investigated by measuring the morphologies and electrochemical impedance of the post-treated io-TiO(2). We found that post-treatment up to a certain period of time increased the surface area and electron lifetime, but further treatment resulted in decreased area and saturated lifetimes. The optimal post-treatment time was identified, and the optimal io-TiO(2) electrodes were characterized.     

Characterizations of white-light ZnWO4 phosphor prepared by blending complementary phosphor

In the preparation of ZnWO₄ phosphor, crystalline ZnWO₄ was created, even though the concentration of WO₃ was only 10 mol%. ZnWO₄ was the dominant crystallization phase when the concentration of WO₃ exceeded 40 mol%. The optimal crystallization of ZnWO₄ phosphor was obtained when the composition molar ratio of ZnO to WO₃ was 1:1, and sintering was carried out at 1,100°C for 3 h. In this condition, a bluish-green emission with a peak at 460 nm was observed. For Y₂O₃:Eu³⁺,Li⁺, the complementary phosphor of ZnWO₄, the Li flux improved phosphor crystallization. The red emission peak of the Y₂O₃:Eu³⁺,Li⁺ phosphor was measured at about 612 nm. The optimal photoluminescence intensity of the Y₂O₃:Eu³⁺,Li⁺ phosphor was obtained when it was sintered at 1,200°C for 5 h and was mixed with 11 mol% Eu₂O₃ and 70 mol% Li₂CO₃. When the weight ratio of Y₂O₃:Eu³⁺,Li⁺ to ZnWO₄ was 1:4, the Y₂O₃:Eu³⁺,Li⁺-blended ZnWO₄ phosphor showed white-light emission with Commission Internationale de l’Eclairage coordinates at (0.34, 0.30). The luminance of the white-light phosphor excited by a 6-W UV lamp was around 160 cd/m².     

Ultra‐Narrow‐Band Blue‐Emitting Oxoberyllates AELi2[Be4O6]:Eu2+ (AE=Sr,Ba) Paving the Way to Efficient RGB pc‐LEDs

Highly efficient phosphor‐converted light‐emitting diodes (pc‐LEDs) are popular in lighting and high‐tech electronics applications. The main goals of present LED research are increasing light quality, preserving color point stability and reducing energy consumption. For those purposes excellent phosphors in all spectral regions are required. Here, we report on ultra‐narrow band blue emitting oxoberyllates AELi₂[Be₄O₆]:Eu²⁺ (AE=Sr,Ba) exhibiting a rigid covalent network isotypic to the nitridoalumosilicate BaLi₂[(Al₂Si₂)N₆]:Eu²⁺. The oxoberyllates’ extremely small Stokes shift and unprecedented ultra‐narrow band blue emission with fwhm ≈25 nm (≈1200 cm^?1) at λ_em=454–456 nm result from its rigid, highly condensed tetrahedra network. AELi₂[Be₄O₆]:Eu²⁺ allows for using short‐wavelength blue LEDs (λ_em<440 nm) for efficient excitation of the ultra‐narrow band blue phosphor, for application in violet pumped white RGB phosphor LEDs with improved color point stability, excellent color rendering, and high energy efficiency.