QUASI-SOLID-STATE DYE-SENSITIZED SOLAR CELLS BASED ON ZnO PHOTOANODE

ZnO photoanode in dye-sensitized solar cells (DSSCs) has been successfully prepared by the electro-hydrodynamic (EHD) technique. The sandwich solar cells exhibited a short-circuit photocurrent density of 7.0 mA cm^-2 and conversion efficiency of 1.65% with a quasi-solid-state electrolyte under simulated sun illumination (AM-1.5, 100 mW cm^-2). The stability and the influencing factors, such as film thickness and light intensity, on solar cell performance were discussed.     

柔性染料敏化太阳能电池材料制备工艺参数的优化

采用水热法制备TiO2纳米浆,与P25粒子和TiO2散射大粒子混合制成级配浆料。将所得的浆料涂敷在铟掺杂氧化锡-聚苯二甲酸乙二醇酯导电聚合物基板上,并在120～150℃进行热处理制成光阳极薄膜。利用溅射法制备Pt对电极,将其组装成柔性的染料敏化太阳能电池(dye-sensitized solar cell,DSC)。研究了对电极溅射时间、TiO2薄膜热处理温度、膜厚以及级配浆料中的酸添加量对电池光电性能的影响。结果表明:当对电极Pt溅射时间为30s,TiO2薄膜热处理温度为150℃,膜厚为10.5μm,浆料添加0.05mol/LHNO3时,柔性DSC的光电性能最好,光电转换效率可达4.05%。     

四羧基金属酞菁的合成及在染料敏化太阳电池中的应用

以偏苯三酸酐、尿素及相应的金属盐为主要原料,采用固相法合成了中心离子为铁(Ⅱ)、钴(Ⅱ)、镍(Ⅱ)、铜(Ⅱ)和锌(Ⅱ)的5种四羧基金属酞菁(tetracarboxymetallophthalocyanine,Pc)。比较了这些Pc乙醇溶液及其敏化的纳米TiO2薄膜的紫外-可见(ultraviolet-visible,UV-Vis)光谱,利用循环伏安法研究了它们的氧化还原行为,并测量了由其组装的染料敏化太阳电池(dye-sensitized solar cells,DSCs)的光伏性能。结果表明:随中心离子价层d电子数的增多,Pc的UV-Vis光谱中Q带最大吸收峰发生位移,由FePc的670nm分别红移至CoPc的674nm,NiPc的676nm,CuPc的679nm和ZnPc的681nm;在N,N-二甲基甲酰胺中,相应Pc的中心离子氧化电势分别为1.01,0.96,0.94,0.99V和1.07V,在组装的5种DSCs中,ZnPc具有相对高的光电转换效率。     

Rapid synthesis and dye-sensitized solar cell applications of hexagonal-shaped ZnO nanorods

This paper reports, for the first time, a very rapid and large-scale synthesis and dye-sensitized solar cells (DSSCs) application of well-crystallized hexagonal-shaped ZnO nanorods at very low temperature of about 70 °C in 20 min. The thin films of as-grown nanorods were used as photo-anode materials to fabricate the DSSCs which exhibited an overall light to electricity conversion efficiency (ECE) of 1.86% with a fill factor of 74.4%, short-circuit current of 3.41 mA/cm² and open-circuit voltage of 0.73 V.     

Growth of Comb-like ZnO Nanostructures for Dye-sensitized Solar Cells Applications

Dye-sensitized solar cells (DSSCs) were fabricated by using well-crystallized ZnO nanocombs directly grown onto the fluorine-doped tin oxide (FTO) via noncatalytic thermal evaporation process. The thin films of as-grown ZnO nanocombs were used as photoanode materials to fabricate the DSSCs, which exhibited an overall light to electricity conversion efficiency of 0.68% with a fill factor of 34%, short-circuit current of 3.14 mA/cm², and open-circuit voltage of 0.671 V. To the best of our knowledge, this is first report in which thin film of ZnO nanocombs was used as photoanode materials to fabricate the DSSCs.     

Controlled synthesis of various ZnO nanostructured materials by capping agents-assisted hydrothermal method for dye-sensitized solar cells

In this work, the morphology of ZnO materials could be controlled by changing the capping agent at constant alkali solution in hydrothermal process. ZnO nanomaterials with the structure of flowers, sheet-spheres and plates were obtained with the capping agent of ammonia, citric acid and oxalic acid, respectively. Thus prepared ZnO nanomaterials were characterized and applied as the photo-anode materials for dye-sensitized solar cell. All synthesized ZnO nanomaterials possessed high crystalline wurtzite structures grown in the (0 0 1) direction with the size of 2-4 μm, which consist of ZnO units around 20-400 nm. Among them, Sheet-sphere ZnO showed the highest crystallinity, surface area and uniform film morphology, resulting in the significantly improved PV performance with the overall conversion efficiency of 2.61% in dye-sensitized solar cell (DSSC) fabricated with sheet-sphere ZnO. It is notable that the ZnO materials with sphere structure may be the optimal photo-anode material among various ZnO nanomaterials for DSSC.     

ZnO nanosphere fabrication using the functionalized polystyrene nanoparticles for dye-sensitized solar cells

The nano-hollow spherical ZnO (NHS ZnO) photoelectrodes were prepared using functionalized polystyrene nanoparticles with flexible dimensional control of the particle diameter for dye-sensitized solar cells applications. NHS ZnO was formed by ZnO nanoparticles that accumulated on the surface of functionalized polystyrene with a high ionic strength. This method represents a one-step preparation method for an inorganic shell via polymerization between ZnO complexes. Even though NHS ZnO has a submicron size, it composed of nanoparticles that connect with each other, thereby implying good electron transfer properties, and has a high surface area. The submicron-sized diameter NHS ZnO has an enhanced light scattering capacity, which promotes the photons with more opportunities to be absorbed by the N719 dye molecules. Therefore, the ZnO films prepared from 600 nm to 1000 nm NHS ZnO possessed higher IPCE values over a wide range (from 400 nm to 750 nm) compared to films of the 300 nm ZnO due to the enhanced light scattering capacities of the film. In photocurrent-voltage measurements, the short-circuit current density of 300 nm and 600 nm NHS ZnO increases from 3.33 mA/cm² to 6.53 mA/cm² while the cell efficiency increases from 1.04% to 3.02% due to the light scattering efficiency. Electrochemical impedance spectroscopy showed that electrons in NHS ZnO with a larger particle size have a longer electron lifetime than NHS ZnO with a smaller particle size, as the latter hinders the electron transport in the NHS ZnO nanostructured films.     

Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices.     

Polymer–metal complex as gel electrolyte for quasi-solid-state dye-sensitized solar cells

A kind of polymer–metal complex gel electrolyte is successfully prepared and is used in dye-sensitized solar cells. Raman and X-ray photoelectron spectroscopy confirm the structure of this complex and is found that the metal ion reacts with nitrogen in the polymer. This novel electrolyte shows apparent diffusion coefficient of iodide of 8.37 × 10⁻⁷ cm² s⁻¹ and the energy conversion efficiency of 6.10% when the amount of ZnI₂ is 0.04 M. By studying the dissociation active energy of the inorganic salt in electrolytes, we find that the metal salts can dissociate more easily after reacting with polymer and as a result can provide extra free iodide ion. The cell maintains ca. 93% of its initial efficiency after 20 d without further sealing, which shows good long-time stability.     

Novel ZnO microflowers on nanorod arrays: local dissolution-driven growth and enhanced light harvesting in dye-sensitized solar cells

ZnO nanostructures were manipulated, via a low-temperature solution process, from pure nanorod arrays to complex nanostructures of microflowers on nanorod arrays with adjusted quantities of flowers. We proposed the mechanism of local dissolution-driven growth to rationally discuss the novel growth process. These nanostructures were used as photoanodes in dye-sensitized solar cells. Compared to pure nanorod arrays, the nanorod array-microflower hierarchical structures improved the power conversion efficiency from 0.41% to 0.92%, corresponding to a 124% efficiency increase. The enhancement of the efficiency was mainly ascribed to the synergistic effect of the enhanced surface area for higher dye loading and the improved light harvesting from efficient light scattering. Present results provide a promising route to improve the capability of light-harvesting for ZnO nanorod array-based DSSCs.     

染料敏化太阳能电池的二氧化钛膜性能研究

以二氧化钛(Ti02)纳米粉(P25)为原料，把它研磨成胶状，用涂敷法制得TiO2纳米多孔膜，并组装成太阳能电池，用100W氙灯作为模拟太阳光，对电池进行光电性能测试．根据电池的短路电流(Isc)、开路电压(Voc)和填充因子(ff)等指标来反映电池的性能．研究表明，分散剂乙酰丙酮、OP乳化剂、研磨时间和热处理后的保温时间长短对TiO2膜的性能均有很大的影响．其结果是，乙酰丙酮0．15mL、OP乳化剂0．10mL、研磨时间1h和保温时间0．5h时，TiO2膜的光电性能较好，JIsc,Voc和ff分别为8．85mA、567mV和0．445．并用XRD和比表面及孔隙分析仪对TiQ2膜进行了表征．     

Solid-state dye-sensitized hierarchically structured ZnO solar cells

A novel solid-state hierarchically structured ZnO dye-sensitized solar cell (DSC) was assembled by using TiO₂ as filler in polyethylene oxide (PEO)/polyethylene glycol (PEG) electrolytes and ZnO nanocrystalline aggregates as photoanode film. Under optimized composite polyelectrolyte containing PEO/oligo-PEG/TiO₂/LiI/I₂ the photovoltaic performance of the solid-state ZnO DSCs was significantly better, with an overall conversion efficiency (η) of 1.8% under irradiation of 100 mW/cm², which was higher than those of the cells with PEO/TiO₂/LiI/I₂ (η = 1.1%) or PEO/oligo-PEG/LiI/I₂ electrolyte (η = 1.5%). Further, the hierarchically structured ZnO-based cell showed a higher η value of 2.0% under 60 mW/cm² radiation. The morphologies, ionic conductivity of three different composite electrolytes and their performance to the DSCs were also studied by FESEM, I–V data, IPCE and EIS.     

TiO2薄膜的制备方法及其对染料敏化太阳电池性能的影响

采用溶胶-凝胶、浆体涂敷、磁控溅射等方法制备了二氧化钛单层以及多层膜．通过透射电镜、扫描电镜以及X射线衍射实验分析了不同薄膜的结构．通过比较不同薄膜制作的染料敏化太阳电池性能探讨了薄膜结构的影响．实验所获得的电池开路电压可达708mV，短路电流可达13．26mA(电池面积为1．8cm^2)．     

太阳能电池无铅导电电极的制备及电性能研究

以Bi2O3、B2O3和SiO2为主要原料制备无铅玻璃粘合剂,将其与导电银(Ag)粉、Al2O3、MnO2等无机添加剂和α-松油醇等有机载体进行混合制备无铅导电银浆,在800℃的温度下烧结20s形成Ag电极。采用四点探针法测量Ag电极电阻率ρ,通过SEM观察其断面形貌并用Keithley2400数字源表测定电池的相关性能参数,研究了Ag电极中导电Ag粉含量对电极性能的影响,确定了无铅导电Ag浆的质量配比为:导电银粉75%,玻璃粘合剂(Glass frit,GF)4%,无机添加剂1%,有机载体20%时,Ag电极的电性能趋于最佳。     

Surface plasma resonant effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells

In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods.     

Ionic liquid/polymer composite electrolytes by in situ photopolymerization and their application in dye-sensitized solar cells

A new kind of quasi-solid state electrolytes for dye-sensitized solar cells (DSCs) has been prepared by in situ photopolymerization from the precursor 1,6-hexanediol diacrylate (HDDA) in 1-hexyl-3-methyl imidazolium iodide (HMII). The optimal ratio of polymer/ionic liquid is determined by the conductivities of the electrolytes. In order to further increase the miscibility between ionic liquid and the polymer, oligomer polyethylene glycol dimethyl ether (PEGDME) is introduced. By optimization of the amount of PEGDME in the electrolyte, the DSCs using this kind of solid-state electrolytes can present 6.5% of light-to-electricity conversion efficiency under 41 mW cm⁻². In the meantime, the influence of PEGDME additive is detailedly investigated by electrochemical impedance spectrum (EIS) and intensity modulated photovoltage spectroscopy (IMVS) techniques. Preliminary long-term stability test revealed that this in situ photopolymerized electrolyte exhibits good stability after 1000 h thermal test.     

ZnO photoanodes with different morphologies grown by electrochemical deposition and their dye-sensitized solar cell properties

In this article, we grew zinc oxide (ZnO) samples with different morphologies, e.g. film, nanowire and nanosheet, with electrochemical deposition (ECD) by controlling the precursor concentration and the growth mechanism was also discussed. The morphology influence on the photovoltaic conversion efficiency of the dye-sensitized solar cells (DSSC) assembled with different ZnO photoanodes was investigated by measuring current density–voltage (J–V) curve, quantum efficiency (QE) spectrum and electrochemical impedance spectrum (EIS). It was found that the DSSC constructed with ZnO nanowire array as photoanode can absorb more dye, improve the photon utilization rate and provide rapid collection channels for the photoexcited carriers. Therefore, the photovoltaic conversion efficiency of ZnO nanowire DSSC was improved.     

The influence of tetrapod-like ZnO morphology and electrolytes on energy conversion efficiency of dye-sensitized solar cells

Tetrapod-like ZnO nanostructures prepared by dc plasma technology were used as photoelectrodes in dye-sensitized solar cells (DSSCs). Each of the tetrapod-like ZnO possesses four extended arms that offer improved electron transport properties. Tetrapod-like ZnO with short (S-ZnO) and long arms (L-ZnO) were synthesized by controlling the plasma gas flow and the input power. Between these two tetrapod-like ZnO nanopowders, the DSSCs using S-ZnO showed higher energy conversion efficiency than using L-ZnO. This is due to the resulting increase in dye adsorption and enhanced short-circuit current density, using S-ZnO. Electrochemical impedance spectroscopy (EIS) shows that the properties of electron transport of S-ZnO are superior to that of the L-ZnO. We investigated the effect of the redox electrolytes (I₂) and the additives (LiI and TBP) on the performance of the DSSCs by intensity-modulated photovoltage spectroscopy and EIS.     

In vitro toxicity of different-sized ZnO nanoparticles in Caco-2 cells

There has been rapid growth in nanotechnology in both the public and private sectors worldwide, but concern about nanosafety exists. To assess size-dependent cytotoxicity on human cancer cells, we studied the cytotoxic effect of three kinds of zinc oxide nanoparticles (ZnO NPs) on human epithelial colorectal adenocarcinoma (Caco-2) cells. Nanoparticles were first characterized by size, distribution, and intensity. Multiple assays have been adopted to measure the cell activity and oxidative stress. The cytotoxicity of ZnO NPs was time dependent and dose dependent. The 24-h exposure was chosen to confirm the viability and accessibility of the cells and taken as the appropriate time for the following test system. The IC₅₀ value was found at a low concentration. The oxidative stress elicited a significant reduction in glutathione with increase in reactive oxygen species and lactate dehydrogenase. The toxicity resulted in a deletion of cells in the G1 phase and an accumulation of cells in the S and G2/M phases. One type of metallic oxide (ZnO) exerted different cytotoxic effects according to different particle sizes. Data from the previous experiments showed that 26-nm ZnO NPs appeared to have the highest toxicity to Caco-2 cells. The study demonstrated the toxicity of ZnO NPs to Caco-2 cells and the impact of particle size, which could be useful in the medical applications.     

Open structure ZnO/CdSe core/shell nanoneedle arrays for solar cells

Open structure ZnO/CdSe core/shell nanoneedle arrays were prepared on a conducting glass (SnO₂:F) substrate by solution deposition and electrochemical techniques. A uniform CdSe shell layer with a grain size of approximately several tens of nanometers was formed on the surface of ZnO nanoneedle cores after annealing at 400°C for 1.5 h. Fabricated solar cells based on these nanostructures exhibited a high short-circuit current density of about 10.5 mA/cm² and an overall power conversion efficiency of 1.07% with solar illumination of 100 mW/cm². Incident photo-to-current conversion efficiencies higher than 75% were also obtained.