TiO2/CdS/CdSe quantum dots co-sensitized solar cell with the staggered-gap (type-II) heterojunctions for the enhanced photovoltaic performance

The effect of co-sensitization and ZnS passivation on the photovoltaic performance of CdS quantum dot sensitized solar cells (QDSSCs) were investigated. The deposition of CdS, CdSe quantum dots (QD) and ZnS passivation on TiO₂ photoanode was carried out by successive ionic layer adsorption and reaction (SILAR) method. CdS/CdSe co-sensitization developed two staggered type-II heterojunctions at TiO₂/CdS and CdS/CdSe interfaces and resulted a cascade energy band structure. This suitable band alignment facilitated the double charge transfer mechanism at each heterojunction and transported the electrons easily into the photoanode. The narrow bandgap sensitizers CdS and CdSe significantly improved the potential utilization of solar spectrum with more charge carrier generation. ZnS passivation on QD surface suppressed electrode/electrolyte interfacial charge recombination and facilitated more electron injection from QDs into TiO₂ photoanode. The EDAX elemental mapping results inferred that CdS, CdSe and ZnS have efficiently covered the TiO₂ surface. TiO₂/CdS and CdS/CdSe interfaces and the amorphous nature of ZnS could be verified with HRTEM images. Hence, the co-sensitization and surface passivation played a significant role to enhance the PCE of CdS QDSSC from 1.9% to 4.05%.     

Effect of CdSe quantum dots on the performance of hybrid solar cells based on ZnO nanorod arrays

This paper reports the fabrication and interface modification of hybrid inverted solar cells based on ZnO nanorod arrays and poly (3-hexylthiophene). CdSe quantum dots (QDs) are grafted to the ZnO nanorod array successfully by bifunctional molecule mercaptopropionic acid to enhance the device performance. The power conversion efficiency of the device is increased by 109% from 0.11% to 0.23% under simulated 1 sun AM 1.5 solar illumination at 100 mW/cm² after the modification. The grafting of CdSe QDs effectively enhanced the excition generation and dissociation on the organic/inorganic interface. This work may provide a general method for increasing the efficiency of organic–inorganic hybrid solar cells by interface modification.     

Fabrication of carboxyl functionalized CdSe quantum dots via ligands self-assembly and CdSe/epoxy fluorescence nanocomposites

A facile approach to introduce carboxyl groups onto the surface of CdSe quantum dots (QD) was achieved via oleic acid ligands self-assembly, and then CdSe quantum dots/epoxy fluorescence nanocomposites were successfully fabricated. The surface constitution of QD, the better dispersibility of QD in epoxy matrix, and the reactivity with epoxy of carboxyl groups functionalized QD were characterized by Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), respectively. As the result of surface modification, the carboxyl groups functionalized QD could be stably and homogenously dispersed in chloroform and acid anhydride cured epoxy matrix. The fresh fluorescence as well as the toughening behavior of the QD/epoxy nanocomposites was presented.     

Capability of coupled CdSe/TiO2 heterogeneous structure for photocatalytic degradation and photoconductivity

Highly ordered TiO₂ nanotube arrays (TiO₂-NTAs), with a uniform tube size on titanium substrate, were obtained by means of reoxidation and annealing. A composite structure, CdSe quantum dots@TiO₂ nanotube arrays (CdSe QDs@TiO₂-NTAs), was fabricated by assembling CdSe quantum dots into TiO₂-NTAs via cyclic voltammetry electrochemical deposition. The X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), and transmission electron microscope (TEM) were carried out for the determination of the composition and structure of the tubular layers. Optical properties were investigated by ultraviolet-visible spectrophotometer (UV-Vis). Photocurrent response under visible light illumination and photocatalytic activity of samples by degradation of methyl orange were measured. The results demonstrated that the photo absorption of the composite film shifted to the visible region, and the photocurrent intensity was greatly enhanced due to the assembly of CdSe QDs. Especially, photocurrent achieved a maximum of 1.853 μA/cm² after five voltammetry cycles of all samples. After irradiation under ultra violet-visible light for 2 h, the degradation rate of composition to methyl orange (MO) reached 88.20%, demonstrating that the CdSe QDs@TiO₂-NTAs exhibited higher photocatalytic activity.     

Microstructure,charge carrier conduction mechanism model,dielectric properties and leakage current analysis of Dy2FeMnO6 nanomaterial

The structure, microstructure, charge transport properties, dielectric properties, and leakage current density of Dy₂FeMnO₆ synthesized by the auto combustion method are investigated in this study. The monoclinic crystal structure of the sample with space group P2₁/n was observed. The CoO₆ and MnO₆ octahedra were found distorted and tilted. The calculation of the bond valence sum confirmed the +3 and + 3/+4 oxidation states of Fe and Mn, respectively. The average crystallite, particle, and grain sizes were 43.01, 94, and 187.68 nm, respectively. The anticipated stoichiometry of the constituent elements was confirmed by energy–dispersive X–ray spectra. The frequency–dependent conductivity obeyed Jonscher’s power law, and the frequency exponent associated with this law increased with temperature, indicating the non–overlapping small polaron tunnelling (NSPT) mechanism for charge conduction. The enhancement of the dielectric loss tangent with temperature was consistent with the dc conductivity. The frequency dependence of dielectric properties was explained using Havriliak–Negami formalism. The sample followed Vogel–Fulcher law, which is similar to the relaxor ferroelectrics, and the ferroelectricity increased with frequency. Conduction, migration, and dielectric relaxation all have similar activation energies. The sample exhibited low leakage current density, which followed Schottky emission with a barrier height of 0.02(4) eV. The obtained results were compared with other rare–earth–based double perovskites.     

锌-空气电池Co-PPy-C复合催化剂的电化学性能研究

采用化学氧化聚合法合成了以碳为载体的钴-聚吡咯(PPy)配合物Co-PPy-C,作为气体扩散电极的氧还原催化剂。利用极化曲线、交流阻抗、计时电流等电化学方法测试了其在碱性介质中(6 mol/L KOH)氧气气氛条件下氧还原的催化性能。电极电位在-0.20 V vs.Hg/HgO时,催化剂电流密度达到158 mA/cm2,显示出优越的氧还原电催化性能;采取催化层/集流体/气体扩散层的排布方式,以纯锌为负极,6 mol/L的KOH为电解液,将气体扩散电极与锌负极组装成锌-空气电池。电池以80 mA/cm2进行恒流放电,放电电压为1.0 V,且性能稳定。     

BRCAA1 antibody- and Her2 antibody-conjugated amphiphilic polymer engineered CdSe/ZnS quantum dots for targeted imaging of gastric cancer

Successful development of safe and highly effective nanoprobes for targeted imaging of in vivo early gastric cancer is a great challenge. Herein, we choose the CdSe/ZnS (core-shell) quantum dots (QDs) as prototypical materials, synthesized one kind of a new amphiphilic polymer including dentate-like alkyl chains and multiple carboxyl groups, and then used the prepared amphiphilic polymer to modify QDs. The resultant amphiphilic polymer engineered QDs (PQDs) were conjugated with BRCAA1 and Her2 monoclonal antibody, and prepared BRCAA1 antibody- and Her2 antibody-conjugated QDs were used for in vitro MGC803 cell labeling and in vivo targeted imaging of gastric cancer cells. Results showed that the PQDs exhibited good water solubility, strong photoluminescence (PL) intensity, and good biocompatibility. BRCAA1 antibody- and Her2 antibody-conjugated QD nanoprobes successfully realized targeted imaging of in vivo gastric cancer MGC803 cells. In conclusion, BRCAA1 antibody- and Her2 antibody-conjugated PQDs have great potential in applications such as single cell labeling and in vivo tracking, and targeted imaging and therapeutic effects'' evaluation of in vivo early gastric cancer cells in the near future.     

Concentration dependence of physical properties of low temperature processed ZnO quantum dots thin films on polyethylene terephthalate as potential electron transport material for perovskite solar cell

Colloidal Zinc oxide quantum dots (ZnO QDs) prepared with varying concentrations through precipitation method were deposited on flexible ITO/PET substrates using spin-coating technique. Various characterization tools were utilized to investigate the morphological, structural, electrical and optical properties of the films. The crystallinity of the films was found to improve with increasing ZnO QD concentration (ZQ_C) as evident from the X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) studies. Crystallographic and optical parameters were evaluated and explained in depth. The average nanograin size and bandgap were increased and decreased respectively, from ～5 nm to ～8 nm and 3.29 eV–3.24 eV with an increase in ZQ_C from 10 mg/mL to 70 mg/mL. Columnar structure growth of the films is revealed by AFM results. The films showed decent optical transparency up to 81%. All the ZnO films exhibited n-type semiconducting property as indicated by the electrical measurements with carrier mobility and low resistivity of 12.21–26.63 cm²/Vs and 11.84 × 10^?3 to 13.16 × 10^?3 Ω cm respectively. Based on the experimental findings, ZnO QD nanostructure film grown at 50 mg/mL is envisaged to be a potential candidate for flexible perovskite photovoltaic application.     

A study of photoluminescence properties and performance improvement of Cd-doped ZnO quantum dots prepared by the sol-gel method

ABSTRACT: In the present work, ZnO quantum dots (QDs) have been prepared by the sol-gel method, and the performance of the QDs have been improved. The effect of Cd concentration on the structural and luminescent properties of the QDs, as well as the effect of the mass ratio of trioctylphosphine oxide (TOPO)/octadecylamine (ODA), has been investigated. The ZnO and Cd-doped ZnO QDs have hexagonal wurtzite structures and are 3~6 nm in diameter. When the Cd content was increased, the QD particle size was reduced; this effect was confirmed in the corresponding ultraviolet-visible (UV) spectra. The fluorescence intensity was simultaneously enhanced significantly. Both the UV and fluorescence spectra were blue-shifted. The luminous intensity was further enhanced when the QDs were modified with TOPO/ODA. FTIR and XRD techniques proved that the polymer successfully coated the surfaces of the QDs. A TOPO/ODA mass ratio of 1:2 was determined to result in the best optical performance among the different ratios examined. The results showed that the described synthetic method is appropriate for the preparation of doped QDs with a high fluorescence quantum efficiency.     

硅橡胶泡沫/HGB复合材料的制备及性能

采用室温硫化法制备了一系列不同空心玻璃微珠（HGB）用量的硅橡胶泡沫（SF）/HGB复合材料,并研究了HGB用量对SF/HGB复合材料的交联密度、泡孔结构、机械性能、动态力学性能的影响。结果表明：HGB用量为6%时对应的SF/HGB6复合材料具有最佳的综合性能。通过静态压缩试验考察了SF/HGB6复合材料的缓冲性能,其缓冲系数与聚乙烯泡沫（EPE）非常接近。动态压缩疲劳试验结果表明,SF/HGB6复合材料具有较长的疲劳寿命（600万次）和较高的高度保持率（98.4%）,远高于EPE（29万次,54.5%）,并且SF/HGB6复合材料的缓冲系数在疲劳试验前后几乎没有变化,明显优于传统的缓冲材料EPE,可作为包装领域的缓冲材料。     

Preparation and performance study of cordierite/mullite composite ceramics for solar thermal energy storage

The employment of solar energy in recent years has reached a remarkable edge. It has become even more popular as the cost of fossil fuel continues to rise. Energy storage system improves an adjustability and marketability of solar thermal and allowing it to produce electricity in demand. This study attempted to prepare cordierite/mullite composite ceramics used as solar thermal storage material from calcined bauxite, talcum, soda feldspar, potassium feldspar, quartz, and mullite. The thermal physical performances were evaluated and characterized by XRD, SEM, EPMA, and EDS. It was found that the optimum sintering temperature was 1280°C for preparing, and the corresponding water adsorption was 11.25%, apparent porosity was 23.59%, bulk density was 2.10 mg·cm^?3, bending strength was 88.52 MPa. The residual bending strength of specimen sintered at 1280°C after thermal shock of 30 times decreased to be 57 MPa that was 36% lower than that before. The thermal conductivity of samples sintered at 1280°C was tested to be 2.20 W·(m·K)^?1 (26°C), and after wrapped a PCM (phase change materials) of K₂SO₄, the thermal storage density was 933 kJ·kg^?1 with the temperature difference (ΔT) ranged in 0‐800°C. The prepared cordierite/mullite composite ceramic was proved to be a promising material for solar thermal energy storage.     

Effect of Al2O3 on the formation of color centers and CdSe/Cd1−xZnxSe quantum dots in SiO2–Na2O–ZnO glasses

color centers and CdSe/Cd_1−xZn_xSe quantum dots (QDs) were formed in silicate glasses, respectively, by carefully adjusting the content of Al₂O₃. The absorption coefficient and broad visible emission at 400-700 nm of color centers increased firstly and then decreased upon increasing concentration of Al₂O₃ from 0 to 5 mol. %. With 2 mol. % Al₂O₃ adding, the band edge emission centered at 497 nm from CdSe QDs in glasses was observed after heat treatment. Raman spectra and TEM characterization confirmed the formation of CdSe/Cd_1−xZn_xSe QDs. The small amount addition of Al₂O₃ had a significant effect on the formation of color centers and precipitation of CdSe/Cd_1−xZn_xSe QDs in glasses due to its complicated effect on the network structure and optical basicity of the glasses.     

Modification of Cr/CrN composite structure by Fe addition and its effect on decorative performance and corrosion resistance

A CrN ceramic coating is a promising substitution for electroplated Cr (Ⅵ) hard coatings; however, it has not yet replaced a decorative Cr (Ⅵ) layer owing to its low reflectivity of visible light and relatively poor corrosion resistance. A Cr/CrN composite structure can address these shortcomings. Our recent work demonstrated that an addition of Fe can facilitate the densification of hot-pressed Cr sputtering targets and enhance the mechanical properties of Cr/CrN composite coatings. In this work, we focus on reporting optical properties and corrosion resistance of the Fe-modified Cr/CrN layers for decorative applications, and clarifying the effect of Fe on these performances. The results show that Fe can increase the amount of metallic phase in the Cr/CrN composite structure and helps enhance its reflectance in the visible region. The composite coating deposited by Cr₉₀Fe₁₀ (at.%) target/alloy exhibits a greater reflectivity of visible light and a better corrosion resistance than those of a single-phase CrN coating. This is attributed to its fine microstructure, which is beneficial for a dense and smooth surface. The color of the coating can be controlled by both the partial pressure ratio of N₂ during deposition and the Fe content in the Cr-Fe sputtering target. The present results show that the addition of Fe can lead to the reduction in the processing cost of Cr targets, enhance the mechanical properties of the composite coatings, and broaden the deposition window. Such cost-effective Fe-modified Cr/CrN composite coatings are expected to be used in various decorative applications.     

Growth and properties of Cu3SbS4 thin films prepared by a two-stage process for solar cell applications

Cu₃SbS₄ is a promising material for thin film heterojunction solar cells owing to its suitable optical and electrical properties. In this paper, we report the preparation of Cu₃SbS₄ thin films by annealing the Sb₂S₃/CuS stacks, produced by chemical bath deposition, in a graphite box held at different temperatures. The influence of annealing temperature on the growth and properties of these films is investigated. These films are systematically analyzed by evaluating their structural, microstructural, optical and electrical properties using suitable characterization techniques. X-ray diffraction analysis showed that these films exhibit tetragonal crystal structure with the lattice parameters a=0.537 nm and b=1.087 nm. Their crystallite size increases with increasing annealing temperature of the stacks. Raman spectroscopy analysis of these films exhibited modes at 132, 247, 273, 317, 344, 358 and 635 cm⁻¹ due to Cu₃SbS₄ phase. X-ray photoelectron spectroscopy analysis revealed that the films prepared by annealing the stack at 350 °C exhibit a Cu-poor and Sb-rich composition with +1, +5 and −2 oxidation states of Cu, Sb and S, respectively. Morphological studies showed an improvement in the grain size of the films on increasing the annealing temperature. The direct optical band gap of these films was in the range of 0.82–0.85 eV. Hall measurements showed that the films are p-type in nature and their electrical resistivity, hole mobility and hole concentration are in the ranges of 0.14–1.20 Ω-cm, 0.05–2.11 cm² V⁻¹ s⁻¹ and 9.4×10²⁰–1.4×10¹⁹ cm⁻³, respectively. These structural, morphological, optical and electrical properties suggest that Cu₃SbS₄ could be used as an absorber layer for bottom cell in multi-junction solar cells.     

Surface compatibility in a carbon-alloy composite and its influence on the electrochemical performance of Li/ion batteries

Carbon-alloy composites were prepared by coating carbon materials with different surfaces with Sn, Sb or SnSb. The SnSb-hard carbon spherule (HCS) composite electrode shows the best cycling performance. The matching of crystalline parameters between SnSb and the carbon ensures a good dispersion of SnSb alloy on the surface. The high density of the nucleation centers on the HCS surface leads to a small SnSb crystallite size. Open pores on the surface of HCS, into which the alloy crystals are allowed to grow, act as pinning centers, which further stabilize the composite. These three factors are supposed to be responsible for the best cyclic performance of SnSb-HCS composite. The latter two factors also result in a large BET surface area, which leads to a large initial irreversible capacity loss, because more solid electrolyte interface film is formed. It seems that the best cyclic performance and the highest initial efficiency are paradoxical in the SnSb-carbon composite. Further surface modification should be conducted to obtain better electrode materials.     

Synthesis and investigation of environmental protection and earth-abundant kesterite Cu2MgxZn1-xSn(S,Se)4 thin films for solar cells

We have synthesized Cu₂Mg_xZn_1–xSn(S,Se)₄ (0?≤?x?≤?0.6) thin films by a facile sol-gel method, and studied the influence of Mg concentration on the crystal structure, surface morphology and photoelectric performance of Cu₂Mg_xZn_1–xSn(S,Se)₄ thin films systematically. It was shown that the smaller Zn²⁺ in Kesterite phase Cu₂ZnSn(S,Se)₄ will be replaced by larger Mg²⁺, forming uniform pure phase Cu₂Mg_xZn_1–xSn(S,Se)₄. The band gap of Cu₂Mg_xZn_1–xSn(S,Se)₄ films can be adjusted from 1.12 to 0.88?eV as the x value changes from 0 to 0.6. Furthermore, the Cu₂Mg_xZn_1–xSn(S,Se)₄ thin films with large grain size, smooth surface and less grain boundaries was obtained at an optimized condition of x?=?0.2. The carrier concentration of Cu₂Mg_xZn_1–xSn(S,Se)₄ thin film reaches the maximum 6.47?×?10¹⁸ cm^?3 at x?=?0.2, which is a potential material to be the absorption layer of high efficiency solar cells.     

GO/PEDOT复合材料修饰阳极的制备及其在MFC中的应用

微生物燃料电池（MFC）是一种利用微生物将有机物中的化学能直接转化成电能的装置,通过改善阳极特性可以有效提高微生物燃料电池的产电性能。通过恒电流法电沉积制备了氧化石墨烯/聚3,4-乙烯二氧噻吩（GO/PEDOT）复合材料修饰碳毡（CF）阳极。通过循环伏安法和交流阻抗法考察了电极特性。将其应用到微生物燃料电池中,对其产电性能进行评价。结果表明,GO/PEDOT-CF电极具有较大的比表面积和优良的电化学性能;以GO/PEDOT-CF为阳极的微生物燃料电池,产电性能良好,其最大功率密度和最大电流密度达到1.138 W·m^-2和4.714 A·m^-2,分别是未修饰阳极的4.80倍和5.51倍。因此,GO/PEDOT复合材料是一种优良的阳极修饰材料,可有效提高MFC的产电性能。     

氮化硅/环氧复合电子基板材料制备及性能

以Si_3N_4粉末作为增强组分与环氧树脂进行复合,采用模压法制备了氮化硅/环氧树脂复合电子基板材料。研究了Si_3N_4含量对复合材料导热性能和介电性能的影响。研究结果表明,随着Si_3N_4含量的增加,复合材料中填料形成导热网络,复合材料的热导率也随之增加,当体积填充量为35%时,导热系数达到1．71 W/m·K。复合材料的介电常数随Si_3N_4含量的增加而增加,但在氮化硅陶瓷颗粒的体积分数达到35%时仍维持在较低的水平(7．08,1 MHz)。     

Chitosan/P3HT biohybrid films as polymer matrices for the in-situ synthesis of CdSe quantum dots. Experimental and theoretical studies

Biohybrid nanocomposite films were obtained through a simple two-step methodology. Films of chitosan/poly(3-hexylthiophene) (CS/P3HT) were used as polymer matrices for the in-situ synthesis and stabilization of CdSe quantum dots. The biohybrid materials were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, UV–visible spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence spectroscopy (PL). The effects of the P3HT composition on the properties of the QDs in the films were analyzed. The results confirmed that CS/P3HT films provided an adequately confining matrix for the growth of CdSe QDs with a fairly uniform size and revealed that the interactions between the CdSe nanoparticles and the CS/P3HT matrix mainly involved the  OH and  NH₂ groups. The optical band gaps of the biohybrid nanocomposite films were estimated. The results of photoluminescence revealed that a charge transfer phenomenon occurred in the polymer system. Finally, theoretical analyses suggest that the CdSe QDs would be preferentially located onto the chitosan domains.     

Structural and optical properties of ITO/TiO2 anti-reflective films for solar cell applications

Indium tin oxide (ITO) and titanium dioxide (TiO₂) anti-reflective coatings (ARCs) were deposited on a (100) P-type monocrystalline Si substrate by a radio-frequency (RF) magnetron sputtering. Polycrystalline ITO and anatase TiO₂ films were obtained at room temperature (RT). The thickness of ITO (60 to 64 nm) and TiO₂ (55 to 60 nm) films was optimized, considering the optical response in the 400- to 1,000-nm wavelength range. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). The XRD analysis showed preferential orientation along (211) and (222) for ITO and (200) and (211) for TiO₂ films. The XRD analysis showed that crystalline ITO/TiO₂ films could be formed at RT. The crystallite strain measurements showed compressive strain for ITO and TiO₂ films. The measured average optical reflectance was about 12% and 10% for the ITO and TiO₂ ARCs, respectively.