A Photoferroelectric Perovskite‐Type Organometallic Halide with Exceptional Anisotropy of Bulk Photovoltaic Effects

Perovskite‐type ferroelectrics composed of organometallic halides are emerging as a promising alternative to conventional photovoltaic devices because of their unique photovoltaic effects (PVEs). A new layered perovskite‐type photoferroelectric, bis(cyclohexylaminium) tetrabromo lead ( 1 ), is presented. The material exhibits an exceptional anisotropy of bulk PVEs. Upon photoexcitation, superior photovoltaic behaviors are created along its inorganic layers, which are composed of corner‐sharing PbBr₆ octahedra. Semiconducting activity with remarkable photoconductivity is achieved in the vertical direction, showing sizeable on/off current ratios (>10⁴), which compete with the most active photovoltaic material CH₃NH₃PbI₃. In 1 the temperature‐dependence of photovoltage coincides fairly well with that of polarization, confirming the dominant role of ferroelectricity in such highly anisotropic PVEs. This finding sheds light on bulk PVEs in ferroelectric materials, and promotes their application in optoelectronic devices.     

Enhanced Electrochemical Performances of LiFePO4/C via V and F Co-doping for Lithium-Ion Batteries

Based on the method of in situ polymerization synthesis combined with two-step sinter-ing process, LiFe_1-xV_x(PO₄)_(3-y)/₃F_y/C was prepared. The e ects of V and F co-doping on the structure, morphology, and electrochemical performances of LiFePO₄/C were in-vestigated by X-ray di raction, Fourier transform infrared spectra, scanning electron mi-croscope, charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results indicated that the V and F co-doping did not destroy the olivine structure of LiFePO₄/C, but it can stabilize the crystal structure, decrease charge transfer resistance, enhance Li ion di usion velocity, further improve its cycling and high-rate capabilities of LiFePO₄/C.     

Synthesis of a BDT-based small-molecule acceptor with dye end groups for organic photovoltaic cell application

ABSTRACT

An acceptor-donor-acceptor (A–D–A)-type small molecule, BDT-IN, having a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as its electron-donating core (D) and an 1,3-indanedione (IN) unit as its electron-withdrawing end group (A), was synthesized by Knoevenagel condensation. The BDT-IN film showed broader UV absorption with a greater red shift (λ_max = 622 nm) than that of the BDT-IN solution (λ_max = 570 nm). The organic photovoltaic cells were fabricated with an ITO/PEDOT:PSS/poly(3-hexylthiophene): BDT-IN/LiF/Al configuration, and showed a power conversion efficiency of 0.23%.     

光伏阵列伏安特性测试系统设计

基于对光伏电站控制和设计水平的要求,本文提出一种基于电容充放电的特性的光伏阵列伏安特性测试系统。本文阐述了测试系统的工作原理和系统关键的部分。当光伏阵列给电容充电时,得到当时环境中光伏阵列的电压、电流以及相应的功率特性曲线。同时对M*N的光伏组件进行建模,得出组件的相应的电性能参数,并对最大功率点进行分析。最后进行实验验证。本测试系统具有测量精度高、系统稳定性高、成本低廉,并且能更直观的测得光伏阵列的特性。     

Donor/conductor/acceptor triads spatially organized on the micrometer-length scale: an alternative approach to photovoltaic cells

We have used porous anodised Al(2)O(3) membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60 microm), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60 microm!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells.     

Photovoltaic properties of tetracene and pentacene layers

Photovoltaic phenomenon in tetracene and pentacene layers evaporated under the same conditions onto a glass substrate and provided with the same couple of electrodes is investigated. Comparison of the results obtained for both organic materials makes it possible to conclude that in spite of differences in mechanisms of charge carrier generation, the values of photovoltaic parameters are very similar.     

Polypyrrole electrodeposition on inorganic semiconductors CuInSe2 and CuInS2 for photovoltaic applications

Thin polypyrrole (PPy) layers with an average thickness of about 0.5 μm were deposited, using potentiostatic and galvanostatic techniques, on CuInSe₂ (CISe) structures prepared electrochemically on glass/ITO substrates and on CuInS₂ (CIS) structures fabricated on Cu tape substrates. The polymer layer of p-type is considered as an alternative to the traditional buffer layer and window layer in the conventional cell structure. The deposition proceeded from an aqueous solution containing sodium naphthalene-2-sulfonate as a dopant. In order to prepare stable PPy films of high quality with a good adherence to the surface of inorganic semiconductors CIS and CISe, the optimal concentrations of reagents, current densities and electrodepositing potentials were selected experimentally. Electrochemical polymerization of pyrrole to PPy on CIS surfaces is faster under white light irradiation and the polymerisation starts at lower potential than in the dark. Significant photovoltage and photocurrent of the fabricated CISe/PPy and CIS/PPy structures have been observed under standard white light illumination.     

Al2O3/TiB2/AlN/TiN复合陶瓷材料的力学性能及显微结构

将金属Al、Al3Ti和TiB2以AlTiB中间合金的形式引入Al2O3基体材料中,采用热压原位反应生成法制备了Al2O3/TiB2/AlN/TiN复合陶瓷材料.复合材料在烧结过程处于过渡液相烧结,并有新相AlN和TiN生成;对热压烧结后材料的硬度、断裂韧性和抗弯强度进行了测试和分析;分析了复合材料力学性能随AlTiB体积百分含量的变化规律;探讨了复合材料断面断裂方式的变化对其力学性能的影响;并对AlTiB中间合金的细化特性进行了分析.     

A solution-processable small-organic molecules containing carbazole or phenoxazine structure as hole-transport materials for perovskite solar cells

Three low molecular weight compounds bearing carbazole units (1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9-yl}hexane and 9,9'-di{6-[3-(2-(4-methylphenyl)vinyl)-9-carbazol-9-yl]hexyl}-[3,3']bicarbazole) and phenoxazine structure (10-butyl-3,7-diphenylphenoxazine) were tested as hole-transporting materials in perovskite solar cells. Two of them were successfully applied as hole transporting layers in electroluminescent light emitted diodes. The examined compounds were high-thermally stable with decomposition temperature found at the range of 280–419 °C. Additionally, DSC measurement revealed that they can be converted into amorphous materials. The compounds possess adequate ionization potentials, to perovskite energy levels, being in the range of 5.15–5.36 eV. The significant increase in power conversion efficiency from 1.60% in the case of a device without hole-transporting layer, to 5.31% for device with 1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9- yl}hexane was observed.