Effective Improvement of the Photovoltaic Performance of Carbon-Based Perovskite Solar Cells by Additional Solvents

A solvent-assisted methodology has been developed to synthesize CH_3NH_3 PbI_3perovskite absorber layers.It involved the use of a mixed solvent of CH_3NH_3 I,PbI_2,c-butyrolactone,and dimethyl sulfoxide(DMSO) followed by the addition of chlorobenzene(CB).The method produced ultra-flat and dense perovskite capping layers atop mesoporous TiO_2 films,enabling a remarkable improvement in the performance of free hole transport material(HTM) carbon electrode-based perovskite solar cells(PSCs).Toluene(TO) was also studied as an additional solvent for comparison.At the annealing temperature of 100 °C,the fabricated HTM-free PSCs based on drop-casting CB demonstrated power conversion efficiency(PCE) of 9.73 %,which is 36 and 71 % higher than those fabricated from the perovskite films using TO or without adding an extra solvent,respectively.The interaction between the PbI_2–DMSO–CH_3NH_3I intermediate phase and the additional solvent was discussed.Furthermore,the influence of the annealing temperature on the absorber film formation,morphology,and crystalline structure was investigated and correlated with the photovoltaic performance.Highly efficient,simple,and stable HTM-free solar cells with a PCE of 11.44 % were prepared utilizing the optimum perovskite absorbers annealed at 120 °C.

Fabrication and Evaluation of Low-cost Cu_2ZnSn(S,Se)_4 Counter Electrodes for Dyesensitized Solar Cells

We explore a simple and eco-friendly approach for preparing CZTS powders and a screen-printing process for Cu_2ZnSn(S,Se)_4(CZTSSe) counter electrodes(CEs) in dye-sensitized solar cells(DSCs). Cu_2ZnSnS_4(CZTS) nanoparticles have been synthesized via a hydrazine-free solvothermal approach without the assistance of organic ligands. CZTS has been prepared by directly drop-casting the CZTS ink on the cleaned FTO glass, while CZTSSe CEs have been fabricated by screen-printing CZTS pastes, followed by post selenization using Se vapor obtained from elemental Se pellets. The crystal structure, composition and morphology of the as-deposited CZTS nanoparticles and CZTSSe electrodes are characterized by X-ray diffractometer, energy dispersive spectrometer, field emission scanning electron microscopy and transmission electron microscopy.The electrochemical properties of CZTS, CZTSSe and Pt CE based DSCs are examined and analyzed by electrochemical impedance spectroscopy. The prepared CZTS and CZTSSe CEs exhibit a cellular structure with high porosity. DSCs fabricated with CZTSSe CEs achieve a power conversion efficiency of 5.75% under AM 1.5 G illumination with an intensity of 100 m W/cm^2, which is higher than that(3.22%) of the cell using the CZTS CE. The results demonstrate that the CZTSSe CE possesses good electrocatalytic activity for the reduction of charge carriers in electrolyte. The comprehensive CZTSSe CE process is cheap and scalable. It can make large-scale electro-catalytic film fabrication cost competitive for both energy harvesting and storage applications.

Giant Magneto-impedance Effect in Composite Wires with Different Core Layer

Composite structure materials were potential sensing elements for magnetic sensors due to Giant magnetoimpedance(GMI) effect. Two kinds of composite wires with different magnetic/non-magnetic structures were fabricated by using electroless deposition methods and the magnetoimpedance properties were investigated. The maximum GMI ratio of 114% was acquired at 60 MHz in the composite wires with a ferromagnetic core, whereas, 116% of maximum GMI ratio was found in the composite wires with a conductive core at low frequency of 600 k Hz. These results exhibit that the GMI ratio reaches the maximum when magnetoresistance ratio ?R/R and magnetoinductance ratio ?X/X make the comparative contributions to the total magnetoimpedance(MI). The obvious GMI effect obtained in the composite wires with conductive core frequency may provide a candidate for applications in magnetic sensors, especially at low frequencies.

Influence of an Electronic Field on the GMI Effect of Fe-based Nanocrystalline Microwire

In this work, a Fe-based nanocrystalline microwire of 20 mm in length and 25 μm in diameter was placed in the center of a 316 stainless steel pipe. The pipe was 500 μm in diameter and a little shorter than the microwire. A series of voltages were applied on the pipe to study the influence of the electrical field on the Giant-Magneto-Impedance(GMI) effect of the microwire. Experimental results showed that the electronic field between the wire and the pipe reduced the hysteresis of the GMI effect. The results were explained based on equivalent circuit and eddy current consumptions analysis.

Magneto-Impedance Effect of Composite Wires Prepared by Chemical Plating under DC Current

CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composition, giant magneto-impedance(GMI) effect and magnetic properties were investigated.It was shown that the circumferential domain structure of coating layer was induced by the DC current going through the wires. A maximum GMI ratio of 870% was obtained in the composite wire prepared under 150 m A and tested at 180 k Hz. It is 30 times higher than that of the composite wire plated in the same condition by conventional chemical plating method, indicating that CPUDC is an easy and effective approach to obtain composite wires and its applications will be further extended on magnetic sensors.

Sonochemical synthesis of silver nanoparticles coated copper wire for low-temperature solid state bonding on silicon substrate

Silver nanoparticles (AgNPs) are directly grown on surface of ~25 μm copper wire by ultrasound-assisted chemical reduction. Silver nitrate is used as precursors, when polyvinylpyrrolidone (PVP) is added as a controller of the dimension of AgNPs. Influence of growth parameters such as precursor's concentration, ratio proportion of PVP and ultra-sonication on the growth of AgNPs coating are determined. The best morphology, size of the AgNPs are observed on copper wire. The results show that the copper wire coated with AgNPs of^100 nm diameter exhibits good antioxidation and ohmic contact after sinter on Si substrate at a temperature as low as 320℃, is especially suitable as a substitute for silver paste electrode used in silicon solar cells.

Orange-red emitting Eu^(2+)-activated(Sr_(0.883)Ba_(0.1)Lu_(0.0.17))_3(Si_(0.95)Al_(0.05))O_5 phosphor: structure, photoluminescence, and application in white LEDs

Orange-red emitting （Sr0.883–xBa0.1Lu0.0.17Eux）3（Si0.95Al0.05）O5 phosphors were synthesized by conventional solid-state reac-tion. The effect of NH4F flux on structural and luminescent properties of phosphors was investigated. Results suggested that the opti-mal content of NH4F flux was 3 wt.%and the optimal doping concentration of Eu2＋was x=0.023 mol. The phosphors showed intense absorption in near-ultraviolet to blue region and exhibited orange-red emissions. The thermal stability of synthesized （Sr0.86Ba0.1Lu0.017Eu0.023）3（Si0.95Al0.05）O5 phosphor were examined and compared with commercial YAG：Ce3＋ yellow phosphors. Combining an InGaN blue 460 nm chip and a white-emitting （Sr0.86Ba0.1Lu0.017Eu0.023）3（Si0.95Al0.05）O5 phosphor produced a white-light LED, demonstrating CIE chromaticity coordinates of （0.314, 0.329） and a color temperature of 5595 K. All results showed that this phosphor is a promising candidate as orange-red emitting phosphor for white light emitting diode （w-LED） application.

Structure,magnetic properties and giant magneto-striction studies in [Tb/Fe/Dy]_n nano-multilayer film

[Tb/Fe/Dy]n nano-multilayer films, with precise composition of Tb0.27Dy0.73Fe2, were prepared by the multi-targets magnetron sputtering technique at room temperature (sample A) and 300℃ substrate temperature (sample B). Both of the nano-multilayer films show columnar structures perpendicular to the film plane according to the scanning electron microscopy results. The magnetic hysteresis loops and the giant magnetostriction (GMS) property of the two samples indicate the perpendicular anisotropy in them. In spite of the perpendicular anisotropy, both of the samples present GMS effect. In a very low applied field of 0.18 T, the GMS value in sample B is 89.3 ppm, which is about four times of that in sample A, 23.5 ppm. The good low-field GMS effect in sample B might attribute to the Laves phase of R-Fe2 segregated from the amorphous matrix under the thermal annealing of the substrate. The relation between the magnetization process and GMS property of the perpendicular anisotropy nano-multilayer films is further investigated.