Performance of dye-sensitized solar cells based on natural dyes

The natural dyes were successfully extracted from spinach, pitaya pericarp, orange peel, ginkgo leaf, purple cabbage and carrot, and then fabricated a dye-sensitized solar cells (DSSCs). It suggested that the absorption properties of natural dyes were strongly dependent on the types and concentration of pigments, and the purple cabbage exhibited an obvious absorption at 317 nm. Meanwhile, a higher conversion efficiency of 0.157% was obtained as the DSSCs were prepared by using purple cabbage, but the DSSCs showed a poor performance when the carrot was used as natural dyes, just achieved 0.01%. FTIR spectra revealed that purple cabbage showed a better adsorption properties between TiO₂ films and dyes than carrot. The dipping time was further investigated and proved that an optimal dipping time was 6 min, the DSSCs using purple cabbage could achieve 0.146% in photoelectric conversion efficiency.     

纳米TiO2多孔膜的微结构对染料敏化纳米薄膜太阳电池性能的影响

采用溶胶-凝胶方法，在不同的实验条件下获得平均粒径从15到25nm左右的纳米TiO２2颗粒.利用这些颗粒制备出的纳米多孔薄膜，应用于染料敏化纳米薄膜太阳电池. 通过x射线 衍射仪分析，得到TiO２₂颗粒的晶相以及晶粒度大小，用透射电子显微镜观察 了纳米TiO２₂颗粒的形貌和尺寸.应用于太阳电池的纳米TiO２₂多 孔膜，经基于布朗诺尔-埃米特-泰 勒（BET）的多层吸附理论的比表面积测试和孔径分布测试，获得了多孔膜的微 关键词： 溶胶-凝胶法 2')" href="#">纳米TiO２₂ 染料敏化 太阳电池     

Extraction and application of natural pigments for fabrication of green dye-sensitized solar cells

Four dye-sensitized solar cell devices are designed and fabricated based on natural dyes extracted from Celosia Cristata, Saffron, Cynoglossum, and eggplant peel, as photosensitizers. The UV–vis technique has been served to determine maximum absorption of natural extract and pre-dyed photoanode. The Fourier transform infrared (FT-IR) was employed to cover the presence of functional groups. The cyclic voltammetry method has been employed to assess the possibility of charge transfer from dried natural dyes to the photoelectrode. The performance of natural-based dye-sensitized solar cells is determined subsequently. The highest power conversion efficiency was ca. 1.38%, which belonged to Celosia Cristata extract. The devices were examined for higher efficiencies, individually, co-sensitized arrangement and/or in tandem with each other.     

大面积染料敏化太阳电池的串联阻抗特性研究

在电子扩散微分方程的基础上,研究了染料敏化太阳电池光生电流和光生电压随光照强度不同的变化关系.提出敏化太阳电池串联阻抗功率损耗模型,理论模拟了大面积电池（有效面积>1 cm²）光电转换效率随多孔薄膜有效面积宽度变化的曲线、透明导电基底膜与银栅极的比接触电阻以及在不同入射光强下银栅极体电阻对大面积染料敏化太阳电池光伏性能的影响.结果表明透明导电基底膜的方块电阻和银栅极体电阻对大面积染料敏化太阳电池的性能有很大影响,而这种影响随光强的减弱逐渐减小. 关键词： 染料敏化 太阳电池 串联阻抗 光电转换效率     

Influence of anthocyanin co-pigment on electron transport and performance in black rice dye-sensitized solar cell

This work reports the novel contribution of chlorophyll b as natural anthocyanin co-pigment in unpurified black rice extract for improved electron transport and performance of natural dye-sensitized solar cell. The dyes are extracted as prominent photosensitizers by considering the concentration, the dye electronic structure, the extraction, and immersion time. The anthocyanin dye containing 1.92 mM cyanidin-3-O-glucoside structure has been extracted without purification. Interestingly, 0.33 mM chlorophyll b is found as a natural co-sensitizer in unpurified anthocyanin. The role of chlorophyll b supporting the electron transfer of anthocyanin dye will be investigated for improved cell performance. Both purified and unpurified dyes are compared in the same anthocyanin concentration. The combined Tauc plot and voltametric method will be conducted to show the interfacial electronic band edges of TiO₂-dye-electrolyte. Electrochemical impedance spectroscopy method will investigate electron transfer dynamic in both cell systems. As a result, chlorophyll b has dominantly acted as two intermediate states in boosting electron injection and dye regeneration to improve cell efficiency from 1.31 to 2.17 % due to the narrower LUMO–TiO₂ conduction band gap and the narrower HOMO-iodide (I ^?) potential gap, respectively. According to the electron transport, the co-sensitizer contributes to the smaller transport resistance (R _t?=?21.9 Ω), the higher chemical diffusion coefficient (D_n?=?1.696?×?10^?3 cm²/s), the higher chemical capacitance (C_μ?=?14.32 μF), and the faster electron transport (τ_d?=?39.88 μs).     

Preparation and improvement in photovoltaic performance of dye-sensitized solar cells using carbon dioxide

We report preparation and improvement in photovoltaic performance of N719-based dye-sensitized solar cells (DSSCs) using pressurized carbon dioxide (CO₂) as a co-solvent for the absorption process on the TiO₂ photoelectrode surface. Effective absorption of the N719 molecules on the TiO₂ surface was achieved using CO₂ processing, and the absorption time was shortened drastically from 24 h (in the dip process) to less than 3 h. The cells prepared under pressurized CO₂ for the absorption showed greater photovoltaic performance, especially higher short-circuit current density and conversion efficiency, compared with that from typical dip method. It was revealed that the suitable CO₂ pressure for the absorption was 5 MPa and the efficiency was achieved to be more than 7.5 %. Prevention of back electron transfer reactions from TiO₂ to oxidized dyes or iodides was caused currently, because the homogeneous coverage of N719 molecules on the TiO₂ surface was obtained by the use of pressurized CO₂.     

基于薄膜电极溶胶修饰的染料敏化太阳电池光电特性研究

染料敏化太阳电池(DSC)中的纳米薄膜电极 是决定太阳电池光电转换性能的重要组成部分. 为改善薄膜电极特性, 采用了不同浓度的TiO₂溶胶对DSC光阳极导电玻 璃和纳米TiO₂多孔薄膜进行不同方式的界面处理. 利用X射线衍射方法对制备得到的多孔薄膜以及溶胶经高温处理 后致密层中纳米TiO₂颗粒的尺寸及晶型进行了测试. 采用高分辨透射电子显微镜和场发射扫描电子 显微镜观察了纳米颗粒及薄膜微结构形貌. 采用强度调制光电流谱/光电压谱分析了TiO₂溶 胶的不同处理方式对电子传输和复合的影响. 在100 mW· cm^-2光强以及暗环境下分别测试了DSC的伏安输出性能以及暗电流. 结果表明, 不同浓度和处理方式均能较好地抑制暗电流. 溶胶处理后光生电子寿命τ_n延长, 电子传输平均时间τ_d相应缩短. 采用浓度为0.10 mol·L^-1的 溶胶对导电玻璃和多孔膜同时处理, DSC的宏观输出特性最佳, 短路电流密度J_sc提高了10.9%, 光电转换效率η提高了11.9%.     

Zinc oxide nanostructures for applications as ethanol sensors and dye-sensitized solar cells

ZnO nanostructures were prepared by thermal oxidation technique for applying as ethanol sensors and dye-sensitized solar cells. To improve sensitivity of the sensor based on ZnO nanostructures, gold doping was performed in ZnO nanostructures. Gold-doped with 0%, 5%, and 10% by weight were investigated. The improvement of sensor sensitivity toward ethanol due to gold doping was observed at entire operating temperature and ethanol concentration. The sensitivity up to 145 was obtained for 10% Au-doped ZnO sensor. This can be explained by an increase of the quantity of oxygen ion due to catalytic effect of gold. Also, it was found that oxygen ion species at the surface of the Au-doped ZnO sensor remained O²⁻ as pure ZnO sensor. For dye-sensitized solar cell application, the dye-sensitized solar cell structure based on ZnO as a photoelectrode was FTO/ZnO/Eosin-Y/electrolyte/Pt counter electrode. ZnO with different morphologies of nanobelt, nano-tetrapod, and powder were investigated. It was found that DSSCs with ZnO powder showed higher photocurrent, photovoltage and overall energy conversion efficiencies than that of ZnO nanobelt and ZnO nano-tetrapod. The best results of DSSCs were the short circuit current (J_sc) of 1.25 mA/cm², the open circuit voltage (V_oc) of 0.45 V, the fill factor (FF) of 0.65 and the overall energy conversion efficiency (η) of 0.68%.     

电极表面改性对染料敏化太阳电池性能影响的机理研究

采用强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)技术,从染料敏化太阳电池(DSC)电子传输和复合角度对比了不同光强下导电玻璃表面阻挡层及TiO₂薄膜优化使电池性能改善的内在原因.阻挡层的引入和TiO₂薄膜的优化均通过电沉积法实现.结果表明,对多孔薄膜电极的不同改性均提高了电池的短路电流J_sc和效率η,但对电子传输和复合过程的作用机理有所不同:前者延长了电子寿命τ _n,但电子传输时间τ _d变化不明显;而后者则主要是延长τ _n的同时也缩短了τ _d. 关键词： 染料敏化 太阳电池 调制光电流谱/调制光电压谱 电子输运     

TiCl4处理多孔薄膜对染料敏化太阳电池中电子传输特性影响研究

借助于强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)技术,研究了纳米TiO₂多孔薄膜在TiCl₄溶液处理后组装成的染料敏化太阳电池(DSC)中电子传输和背反应动力学特性. 研究表明:纳米TiO₂多孔薄膜经TiCl₄溶液处理后,电池中暗电流减小,电子寿命τ_n明显延长,电子传输时间τ_d缩短,电子有效扩散系数D_n增大,电子扩散长度L_n值升高,入射单色光子/电子转化效率η_IPCE增加,光生电荷量Q_oc显著增加. 文章从微观层面上研究了TiCl₄溶液处理纳米TiO₂多孔薄膜对DSC内部电子的产生、传输和复合过程的影响,从而很好地解释了电池光伏性能随TiCl₄溶液处理的变化关系. 关键词： 4')" href="#">TiCl₄ 电子传输 染料敏化 太阳电池     

Influence of pyrazole on the photovoltaic performance of dye-sensitized solar cell with polyvinylidene fluoride polymer electrolytes

We investigate the influence of the pyrazole content on the polyvinylidene fluoride (PVDF)/KI/I₂ electrolytes for dye-sensitized solar cells (DSSCs). The solid polymer electrolyte films consisting of different weight percentage ratios (0 20, 30, 40, and 50 %) of pyrazole doped with PVDF/KI/I₂ have been prepared by solution casting technique using N,N-dimethyl formamide (DMF) as a solvent. The as-prepared polymer electrolyte films were characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR spectroscopy), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), alternate current (AC)-impedance analysis, and scanning electron microscopy (SEM). The 40 wt% pyrazole-PVDF/KI/I₂ electrolyte exhibited the highest ionic conductivity value of 9.52?×?10^?5 Scm^?1 at room temperature. This may be due to the lower crystallinity of PVDF and higher ionic mobility of iodide ions in the electrolyte. The DSSC fabricated using this highest ion conducting electrolyte showed an enhanced power conversion efficiency of 3.30 % under an illumination of 60 mW/cm² than that of pure PVDF/KI/I₂ electrolyte (1.42 %).     

Modeling of dye-sensitized titanium dioxide solar cells

The system TiO₂–photo sensitive dye of a dye-sensitized TiO₂ solar cell is numerically simulated. The steady-state numerical model used is based on the continuity and transport equations for all charge species involved in the system, in connection to Poisson’s equation. The dependence of both electron diffusion coefficient and light absorbance upon TiO₂ porosity is taken into consideration. The resulting electron density after illumination is also set as a function of the illuminating beam characteristics and material properties. Furthermore, an effective dielectric constant dependent upon the porosity of TiO₂ is used in the model. Results for different values of pore size and thickness of the TiO₂ electrode are found in accordance with results reported in the literature. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007. An erratum to this article can be found at     

基于半经验模型对大面积染料敏化太阳电池性能影响因素的研究

以影响大面积染料敏化太阳电池性能的几个物理参量和几何参量为切入点, 分析了内部电阻对电池性能的影响, 针对几种构型不同的大面积电池, 建立了效率的半经验模型. 根据并联、串联、和各单元独立式串并联的大面积电池的相关物理参量和几何参量, 对电池效率进行了计算. 通过比较计算值与测试值的偏差, 分析了半经验模型的适用性. 在半经验模型的基础上, 分析了相关物理参量和几何参量对电池性能的影响. 结果表明, 在实际应用中, 通过半经验模型分析物理参量和几何参量的影响, 可以优化大面积电池的性能.     

N, S-doped TiO2 anode effect on performance of dye-sensitized solar cells

The modification of non-metallic elements N and S to nanocrystalline TiO₂ anode results in the energy gap is reduced to 2.63 eV and a strong redshift to the visible region occurred in the UV–visible spectrum. Poly (3-decylthiophene) (P3DT) is synthesized. Ultraviolet–visible spectra (UV–vis) shows that the light absorption of P3DT (Poly (3-decylthiophene)) and N719 (RuL2(NCS)2:2TBA (L=2,2′-bipyridyl-4, 4′-dicarboxylic acid)) are complementary to cover the entire visible region. Solar cell based on N–S/TiO₂ is co-sensitized by P3DT and N719. The photoelectric conversion efficiency of co-sensitized solar cell increases 56.8% comparing with the single dye-sensitized solar cell.     

An investigation of DNA-like structured dye-sensitized solar cells

This paper reports a 3D DNA-like structured dye-sensitized solar cell (DSSC) with all-Ti substrates. A self-organized TiO₂ nanotubular arrays layer was directly grown on the photoanode surface by electrochemical anodization. Compared with the traditional flat-type DSSC, the DNA-like DSSC showed superiority of light utilization due to its symmetrical double-helix structure. Different thickness of the nanotubular arrays layers were investigated to find their influence on the cell’s photovoltaic parameters, and the cell with a 15.3 μm layer exhibited the highest P_max, about 0.49 mW. The series–parallel connection characteristics of the DNA-like DSSCs reveal that the total voltage and the total short current equalled the sum of each cell’s in series and in parallel, respectively. It is anticipated that the novel DNA-like structured DSSCs have great application potential in larger modules using integrated circuit.     

负偏压作用下染料敏化太阳电池界面及光电性能研究

太阳电池组件由于局部电压不匹配,其中部分电池可能较长时间工作在负偏压状态下,从而影响电池光电性能.借助拉曼光谱、电化学阻抗谱和入射单色光量子效率(IPCE)等测试手段,研究长期负偏压作用下染料敏化太阳电池光电性能的变化及其影响机理.拉曼光谱研究结果表明:电池在1000 h负偏压作用下,电解质中阳离子(Li⁺)会向光阳极(TiO₂电极)移动并嵌入TiO₂薄膜中;长期负偏压作用还会致使TiO₂/电解质界面阻抗增大和IPCE下降,导致电池开路电压升高和短路电流减小.通过加入苯并咪唑(BI)添加剂,经1000 h负偏压后电池的拉曼光谱实验表明,BI能在一定程度阻碍Li⁺的嵌入,电池具有较好的长期稳定性.不同负偏压下的老化实验进一步表明,通过加入添加剂能够使电池在长期负偏压下保持较好的稳定性. 关键词： 染料敏化 太阳电池 组件 负偏压