Magnetic carbon nanotubes: synthesis by a simple solvothermal process and application in magnetic targeted drug delivery system

A poly(vinyl chloride) (PVC) main chain was grafted with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) containing a quaternary amine group using atom transfer radical polymerization. The successful synthesis of a PVC-g-PDMAEMA graft copolymer was confirmed by Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, and transmission electron microscopy. The PVC-g-PDMAEMA graft copolymer was used as a structure-directing agent (SDA) for the fabrication of a mesoporous thin film containing a titanium dioxide (TiO₂) layer. To control the porosity of the resultant inorganic layer, the ratio of SDA to TTIP as well as the concentration of the sol?Cgel was varied. The structure and porosity of the mesoporous film were characterized by XRD and SEM analysis. The mesoporous TiO₂ film fabricated on the FTO surface was used as a photoanode for the dye-sensitized solar cell (DSSC). DSSC performance was the greatest when using TiO₂ film with a higher porosity and lower interfacial resistance. The highest energy conversion efficiency reached 3.2?% at 100?mW/cm², which was one of the highest reported values for a quasi-solid-state DSSC with 600-nm-thick TiO₂ film.     

Natural dye-based photoelectrode for improvement of solar cell performance

In the present paper, photovoltaic studies of dye-sensitized solar cells (DSSCs) based on betacyanin/TiO₂ and betacyanin/WO₃–TiO₂ have been done. The cell performances were compared through I–V curves and wavelength dependant photocurrent measurements for the two new types of DSSCs. The TiO₂-coated DSSC showed the photovoltage and photocurrent of 300 mV and 4.96 mA/cm², whereas the cell employing WO₃–TiO₂ photoelectrode showed the values 435 mV and 9.86 mA/cm², respectively. The conversion efficiency of TiO₂ based dye-sensitized solar cell was found to be 0.69 %, while WO₃–TiO₂-based cell exhibited a higher conversion efficiency of 2.2 %. The better performance of the WO₃–TiO₂ dye-sensitized solar cell photoelectrode is thought to be due to an inherent energy barrier at the electrode/electrolyte interface leading to the reduced recombination of photoinduced electrons.     

Poly(vinyl chloride)-<Emphasis Type="Italic">graft</Emphasis>-poly(<Emphasis Type="Italic">N</Emphasis>-vinyl caprolactam) graft copolymer: synthesis and use as template for porous TiO<Subscript>2</Subscript> thin films in dye-sensitized solar cells

Poly(N-vinyl caprolactam) (PNVCL) side chains were grafted to a poly(vinyl chloride) (PVC) backbone via atom transfer radical polymerization. The synthesized PVC-g-PNVCL graft copolymer was templated for the preparation of porous TiO₂ thin films, which involved a sol–gel reaction and calcination process. The interaction of the carbonyl groups in the PVC-g-PNVCL with the titania was revealed by FT-IR spectroscopy. X-ray diffraction and transmission electron microscopy analysis showed the formation of porous TiO₂ thin films with the anatase phase. A series of porous TiO₂ thin films with different pore sizes and porosities was prepared by varying the solution compositions and were used as photoelectrodes in dye-sensitized solar cells (DSSC) with a polymer electrolyte. The DSSC performed best when using the TiO₂ film with higher porosity, lower interfacial resistance, and longer electron life time. The highest energy conversion efficiency, photovoltage (V _oc), photocurrent density (J _sc), and fill factor (FF) were 1.2%, 0.68 V, 3.2 mA/cm², and 0.57 at 100 mW/cm², respectively, for the quasi-solid state DSSC with a 730-nm-thick TiO₂ film.     

TiO2表面质子化对染料敏化太阳能电池性能及吸附染料稳定性的影响

采用致密平整TiO₂薄膜作为染料敏化太阳能电池光电极,并研究了HCl处理表面质子化对电池性能的影响. 结果表明,HCl处理后电池的短路电流显著提升,电池的开路电压则有轻微的下降,电池电流提升了31%,而能量转化效率则提升了25%. 这是因为TiO₂的表面质子化增强了吸附染料与TiO₂间的电学耦合,提高了染料中激发电子向TiO₂导带的注入速率. 而电压的下降,一方面是由于质子化会引起TiO₂导带能级     

Laser Sintering of a Porous TiO2 Film in Dye-Sensitized Solar Cells

We investigate the possibility of modifying the porous structure of TiO₂ films in dye-sensitized solar cells (DSSC) in its sintering by a pulsed Nd:YAG laser (wavelength 1064 nm) to improve their parameters and characteristics. Sintering at various pulse energies enabled a porosity within the range of 0.45 to 0.20. The efficiency of the energy conversion in experimental DSSC specimens with TiO₂ films sintered by an optimum laser-radiation pulse energy of 150 mJ was 20–25% higher than that of commercial solar cells.     

Chemical reactions in TiO2/SnO2/TiCl4 hybrid electrodes and their impacts to power conversion efficiency of dye-sensitized solar cells

This study examined the applicability of TiO₂/SnO₂/TiCl₄ hybrid electrodes in dye-sensitized solar cells (DSSCs) by combining chemical modeling with experimentation. The interfacial chemical reactions in a TiO₂/SnO₂/TiCl₄ system were simulated using a thermochemistry software package, which led to the design and testing of hybrid working electrodes. Chemical thermodynamic modeling proved that TiCl₄ is an effective agent in removing Tiⁿ⁺ (n<4) and Sn^m+ (m<4) ion impurities from dry-mixed TiO₂/SnO₂ composite particles. Our results demonstrate that the power conversion efficiency of DSSC with a TiO₂/SnO₂/TiCl₄ hybrid electrode exceeds that of the conventional DSSC with a TiO₂ electrode due to the effects of light-scattering and the formation of additional absorbance (SnCl₂), which is an unexpected side effect of TiCl₄ treatment enabling the absorption of visible light. The proposed approach is ideally suited to establishing relationships between chemistry theory and the structure and performance of advanced DSSCs as well as photo-electro-chemical systems.     

Enhanced efficiency of dye-sensitized solar cells by UV–O3 treatment of TiO2 layer

Solar conversion efficiency of dye-sensitized solar cells was improved by UV–O₃ treatment of TiO₂ before and/or after sintering. The enhancement was resulted from the removal of the residual organics originated from the TiO₂ precursor pastes, increased adsorption of dyes to the TiO₂, surface, and longer diffusion length and shorter electron transit time of electrons through the TiO₂ mesoscopic structure. The power conversion efficiency of the cells reaches to 7.2% with the open circuit voltage of 0.71 V, the short circuit current density of 15.2 mA/cm² and the fill factor of 0.67 under illumination with AM 1.5 (100 mW/cm²) simulated sunlight.     

Study on the properties and charge generation in dye-sensitized n-TiO2|dye|p-CuI solid state photovoltaic solar cells

Transparent semiconducting copper iodide (CuI) films were prepared by XeCl Excimer laser and their characteristics are investigated. These films exhibited optical transmittance over 80% in the wavelength range from 400 to 900 nm and minimum resistivity of about 2 kΩ cm⁻¹. The optical absorption of the these films shows a remarkable blue shift compared to that of polycrystalline of CuI, which can be explained from the viewpoint formation of ultra fine of CuI grains. The titanium dioxide (TiO₂) films have been prepared by sol-gel method. The properties of pulsed laser deposited CuI and TiO₂ films in power output of n-TiO₂|dye|p-CuI cells is studied. An efficient charge generation is observed through the illumination of TiO₂ layer of the fabricated n-TiO₂|dye|p-CuI solid state photovoltaic solar cells. From the current-voltage characteristics, the fill factor and power conversion efficiency were about of 45 and 3%, respectively. The maximum photo-current of about 12.5 mA/cm² and photo-voltage of 475 mV under AM 1.5 conditions were obtained for the n-TiO₂|dye|p-CuI solid states photovoltaic solar cells with good reproducibility. Adsorbed dye molecules to the TiO₂ surface act as a relay, especially under illumination through TiO₂ layer in the wave range region of 300-400 nm.     

Dye-sensitized solar cells based on ZnO nanowire array/TiO2 nanoparticle composite photoelectrodes with controllable nanowire aspect ratio

The ZnO nanowire (NW) array/TiO₂ nanoparticle (NP) composite photoelectrode with controllable NW aspect ratio has been grown from aqueous solutions for the fabrication of dye-sensitized solar cells (DSSCs), which combines the advantages of the rapid electron transport in ZnO NW array and the high surface area of TiO₂ NPs. The results indicate that the composite photoelectrode achieves higher overall photoelectrical conversion efficiency (η) than the ZnO NW alone. As a result, DSSCs based on the ZnO NW array/TiO₂ NP composite photoelectrodes get the enhanced photoelectrical conversion efficiency, and the highest η is also achieved by rational tuning the aspect ratio of ZnO NWs. With the proper aspect ratio (ca. 6) of ZnO NW, the ZnO NW array/TiO₂ NP composite DSSC exhibits the highest conversion efficiency (5.5 %). It is elucidated by the dye adsorption amount and interfacial electron transport of DSSCs with the ZnO NW array/TiO₂ NP composite photoelectrode, which is quantitatively characterized using the UV-Vis absorption spectra and electrochemical impedance spectra. It is evident that the DSSC with the proper aspect ratio of ZnO NW displays the high dye adsorption amount and fastest interfacial electron transfer.     

Electrodeposition of zinc oxide/tetrasulfonated copper phthalocyanine hybrid thin film for dye-sensitized solar cell application

Hybrid film of zinc oxide (ZnO) and tetrasulfonated copper phthalocyanine (TSPcCu) was grown on an indium tin oxide (ITO) glass by one-step cathodic electrodeposition from aqueous mixtures of Zn(NO₃)₂, TSPcCu and KCl. The addition of TSPcCu strongly influences the morphology and crystallographic orientation of the ZnO. The nanosheets stack of ZnO leads to a porous surface structure which is advantageous to further adsorb organic dyes. The photovoltaic properties were investigated by assembling the DSSC device based on both the only ZnO film and the ZnO/TSPcCu hybrid films. Photoelectrochemical analysis revealed that the optimized DSSC device with TSPcCu represented a more than three-fold improvement in power conversion efficiency than the device without TSPcCu. The DSSC based on ZnO/TSPcCu hybrid films demonstrates an open circuit voltage of 0.308 V, a short circuit current of 90 μA cm⁻², a fill factor of 0.26, and a power conversion efficiency of 0.14%.     

Hydrothermal growth of large-scale macroporous TiO<Subscript>2</Subscript> nanowires and its application in 3D dye-sensitized solar cells

Large-scale macroporous TiO₂ nanowires (MTN) were directly grown on spiral-shaped titanium wires as photoanodes of dye-sensitized solar cells (DSSCs) via a facile hydrothermal reaction without any seeds, templates, and TiO₂ powder. The MTN thin film was characterized by SEM, XRD and TEM. The studies revealed that the MTN thin film had better mechanical properties and provided an efficient pathway for the diffusion of liquid electrolyte. The efficiency of 0.86% for the 3D DSSC was obtained with a J _sc of 2.30 mA/cm², V _oc of 616 mV, and FF of 0.61. This MNT-based mini 3D DSSC is a promising photovoltaic device for applications in the fields of high-integrated micro-electronic equipment.     

A facile low temperature synthesis of TiO2 nanorods for high efficiency dye sensitized solar cells

Titania (TiO₂) nanorods have been synthesized with controlled size for dye-sensitized solar cells (DSSCs) via hydrothermal route at low hydrothermal temperature of 100 °C for 24 h. The titania nanorods were characterized using XRD, SEM, TEM/HRTEM, UV-vis Spectroscopy, FTIR and BET specific surface area (S _BET), as well as pore-size distribution by BJH. The results indicated that the bulk traps and the surface states within the TiO₂ nanorods films have enhanced the efficiency of DSSCs. The size of the titania nanorods was 6.7 nm in width and 22 nm in length. The high surface area can provide more sites for dye adsorption, while the fast photoelectron-transfer channel can enhance the photogenerated electron transfer to complete the circuit. The specific surface area S _BET was 77.14 m²?g^?1 at the synthesis conditions. However, the band gap energy of the obtained titania nanorods was 3.2 eV. The oriented nanorods with appropriate lengths are beneficial in improving the electron transport property and thus leading to the increase of photocurrent, together enhancing the power conversion efficiency. A nearly quantitative absorbed photon-to-electrical current conversion achieved upon excitation at wave length of 550 nm and the power efficiency was enhanced from 5.6 % for commercial TiO₂ nanoparticles Degussa (P25) cells to 7.2 % for TiO₂ nanorods cells under AM 1.5 illumination (100 mW?cm^?2). The TiO₂ cells performance was improved due to their high surface area, hierarchically mesoporous structures and fast electron-transfer rate compared with the Degussa (P25).     

PEO electrolytes containing dioctyl phthalate (DOP) for dye-sensitized nanocrystalline TiO2 solar cells

In this paper, we aim to prepare polymer electrolytes consisting of NaI and I₂ dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared spectra shifted to a lower wave number (Δf = 93 cm⁻¹), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and structural changes of PEO/NaI/I₂/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10^–4 S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P _max/P _in × 100) at one sun condition (100 mW/cm²). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO₂ layers were verified by field-emission scanning electron microscopy.     

Efficient carbon-doped nanostructured TiO<Subscript>2</Subscript> (anatase) film for photoelectrochemical solar cells

In this paper, we have demonstrated that carbon-doped nanostructured TiO₂ (CD ns-TiO₂) films could be prepared simply and cheaply with oxalic acid and tetrabutylammonium bromide (Bu₄N·Br) as the carbon sources. The surface morphology of the films was a multiple-porous network structure.The average size of nanoparticle was about 40 nm. Carbon doped into substitutional sites of TiO₂ has also proven to be indispensable for band-gap narrowing and photovoltaic effect. Carbon doping lowered the band gap of n-TiO₂ to 1.98, 1.64, and 1.26 eV. The CD ns-TiO₂ film was first used as photoanode for solar cells, exhibiting high photocurrent densities (l.34 mA/cm²) and yielding an overall conversion efficiency (η) of 4.42 %.     

Electronic-beam evaporation processed titanium oxide as an electron selective contact for silicon solar cells

This work is dedicated to the study of electronic-beam (e-beam) evaporated titanium oxide (TiO_x) contact for polycrystalline silicon hetero-junction solar cells. A TiO_x material obtained by e-beam evaporation method is suggested as a possible alternative to the atomic layer deposition (ALD) process. The purpose is to achieve corresponding passivation efficiency between e-beam evaporation of TiOx and the ALD method. However, the TiOx in question achieved a relatively low passivation performance of S_eff = 113 cm⁻¹ in comparison to the reported ALD results. Nonetheless, as e-beam evaporation is well-established and an environmentally friendly deposition technology, e-beam evaporated TiO_x passivation layer has potential for improvement. What is clearly demonstrated in our work is how such an improvement in contact resistance dropped from >55 Ω/cm² to 2.29 Ω/cm². Indeed, our study established a correlation between the main process parameters of e-beam evaporation and their influence on the quality of electron selective TiO_x layer. Moreover, we reveal a possible scenario for the implementation of e-beam evaporated Titanium oxide as electron selective contact for asymmetrical hetero-junction solar cells.     

Synthesis of two-dimensional nanowall of Cu-Doped TiO2 and its application as photoanode in DSSCs

Two-dimensional nanowall of Cu-doped TiO₂ (CuTNW) has been prepared in this work to study the role of Cu doping on its photoactivity properties and its photovoltaic performance as photoanode in a dye-sensitized solar cell (DSSC). TiO₂ nanowall with five Cu ion doping, i.e. 6.25, 12.5, 25.0, 50.0 and 100.0 mM, were prepared via a liquid-phase deposition method using ammoniumhexafluorotitanate and hexamethylenetetramine as the reagents with a growth temperature of 90 °C. The X-Ray Diffraction (XRD), X-ray energy dispersion (EDX) and diffuse optical reflectance spectroscopy analysis results confirmed the successfulness of the Cu doping process in the TiO₂ nanowall and effective modification on the photoactivity of the TiO₂ nanowall. We found that the power conversion efficiency of the DSSC utilizing TiO₂ nanowall as photoanode can be enhanced up to 2 times, i.e. from 0.2% to 0.44%, when the TiO₂ nanowall doped with Cu ion. The nanostructure preparation, device fabrication and the mechanism for the device performance enhancement will be discussed.     

Nano TiO2 film electrode for electrocatalytic reduction of furfural in ionic liquids

Nanoporous TiO₂ having enhanced surface area was synthesized by sol–gel method. An “environmental friendly” method for production of furfuryl alcohol was presented by electrocatalytic reduction of furfural to furfuryl alcohol in ionic liquid medium at the surface of nanoporous TiO₂ film electrode. The heterogeneous catalytic redox behaviour of a nanoporous TiO₂ film electrode surface was investigated by cyclic voltammetry (CV). It was found that the catalytic reduction of furfural by Ti(IV)/Ti(III) redox system on the nanoporous TiO₂ film surface. The electrode reaction mechanism is called catalytic (EC′) mechanism, current density can reach 38 mA/cm² and yielding an overall conversion efficiency of 61.7%.     

AZO/Ag/AZO multilayer films prepared by DC magnetron sputtering for dye-sensitized solar cell application

Ag films were deposited on Al-doped ZnO (AZO) films and coated with AZO to fabricate AZO/Ag/AZO multilayer films by DC magnetron sputtering on glass substrates without heating of glass substrates. The best multilayer films have low sheet resistance of 19.8 Ω/Sq and average transmittance values of 61% in visible region. It was found that the highest figure of merit (F_TC) is 6.9 × 10⁻⁴ Ω⁻¹. For the dye-sensitized solar cell (DSSC) application, the multilayer films were used as transparent conductive electrode (multilayer films/ZnO + Eosin-Y/LiI + I₂/Pt/FTO). The best DSSC based on the multilayer films showed that open circuit voltage (V_oc) of 0.47 V, short circuit current density (J_sc) of 2.24 mA/cm², fill factor (FF) of 0.58 and incident photon-to-current conversion efficiency (η) of 0.61%. It was shown that the AZO/Ag/AZO multilayer films have potential for application in DSSC.     

TiO<Subscript>2</Subscript> nanotube height effect on the efficiency of dye-sensitized solar cells

Performance of dye-sensitized solar cells (DSSCs) based on TiO₂ nanotubes (NTs) filled with TiO₂ nanoparticles (NPs) was studied as a function of NT height (h). The NT height was varied in the range of 1.5–7.0 μm, while the NT diameter was kept constant at ~80 nm. The studies showed that DSSC efficiency, current density, and fill factor linearly increased with h and ranged in 1.76–6.5%, 3.62–13.2 mA/cm², and 0.66–0.76, respectively, within the h range studied. The electrochemical impedance spectroscopy was also performed to study DSSC electron transport properties. Based on both photovoltaic and electrochemical impedance spectroscopy data, the results were explained as being due to the increased dye loading that led to higher light-harvesting efficiency.     

质子注入MBE碲镉汞n-on-p结性能研究

基于中波响应波段的分子束外延碲镉汞薄膜材料成功制备出不同质子注入剂量的大光敏元(5 00μm×500μm)的n-on-p结构的p-n结，并对相应的p-n结的电流-电压（I-V）特性进行 了研究.质子注入剂量为2×10¹⁵cm^-2时R₀A达312.5Ω ·cm²，低温热处理后达490Ω·cm². 关键词： I-V特性 碲镉汞薄膜 质子注入 p-n结