Study of graphene nanoflake as counter electrode in dye sensitized solar cells

Graphene nanoflake (GNF) films have been fabricated on a fluorine doped tin oxide (FTO) glass using a doctor blade method and thermally annealed in air and argon ambient at various temperatures. The GNF/FTO thin films were employed as a counter electrode for dye sensitized solar cells (DSSCs). Results showed the GNF/FTO film could enhance the power conversion efficiency (PCE) of DSSC devices more effectively when annealed in argon ambient rather than in air and at annealing temperatures higher than 380 °C. The PCE enhancement was mainly due to the lowered oxygen concentration in the film and the elevated electrical conductance. A PCE of 6.08% or 88% of that with a Pt counter electrode has been achieved for DSSCs with a GNF counter electrode, suggesting that GNF is a highly potential candidate to replace Pt catalyst.     

Synthesis of graphene-CoS electro-catalytic electrodes for dye sensitized solar cells

A large CoS-implanted graphene (G-CoS) film electrode was prepared using chemical vapor deposition followed by successive ionic layer absorption and reaction. HRTEM and AFM show that CoS nanoparticles are uniformly implanted on the graphene film. Furthermore, the G-CoS electro-catalytic electrode is characterized in a dye sensitized solar cells (DSSC) and is found to be highly electro-catalytic towards iodine reduction with low charge transfer resistance (R_ct ～5.05 Ω cm²) and high exchange current density (J₀～2.50 mA cm^?2). The improved performance compared to the pristine graphene is attributed to the increased number of active catalytic sites of G-CoS and highly conducting path of graphene. The comprehensive G-CoS synthesis process is a simple and scalable process which can easily adapt for large scale electro-catalytic film fabrication for several other electro-chemical energy harvesting and storage applications.     

Eosin-G and ethyl eosin dye sensitized CdS nanowires towards dye sensitized solar cells applications

One dimensional (1-D) CdS nanowires have been grown through a low temperature chemical route and have been sensitized with eosin-G and ethyl eosin dyes to broaden the absorption spectrum of CdS and to enhance the photoelectrochemical (PEC) performance under illumination. The used method is advantageous due to its simplicity, low cost, scalability, and controllability. Interestingly, eosin-G and ethyl eosin dyes yield nearly four- and six-fold increase in device efficiency compared to bare CdS when tested in dye-sensitized solar cell assembly. Structural, surface morphological, optical, and surface wettability studies have been formulated for CdS, whereas identification of materials along with PEC investigations were conducted through current density–voltage (J-V), external quantum efficiency (EQE), characteristics under the illumination of 94.6 mW/cm² (AM 1.5G), and electrochemical impedance spectroscopy (EIS).     

天然染料敏化TiO2太阳能电池阳极制备优化条件

从常青树树叶中提取色素作为天然染料,探索了天然染料敏化TiO2太阳能电池阳极制备的优化条件。实验结果表明,乙酰丙酮0.10 mL、OP乳化剂0.10 mL、热处理温度500℃、恒温时间30 min和研磨时间60 min的条件下,天然染料敏化TiO2太阳能电池的开路电压和短路电流达到极大值。进一步比较了常青树树叶、白菜叶、绿茶茶叶等天然染料作为光敏剂对太阳能电池性能的影响,结果绿茶茶叶的光敏化效果最好。     

Synthesis,characterization and simulation of lithium titanate nanotubes for dye sensitized solar cells

In this work we present the comprehensive design of lithium titanate nanotubes (LiTNT) as semiconductors for DSSC photoanodes. The synthesis and characterization of Li_1.82Na_0.18Ti₃O₇.nH₂O nanotubes was performed and a prototype of cell using this material was assembled. The cell exhibited a 7.7% efficiency and a relatively high open circuit voltage, Voc?=?0.72?V. In comparison with previously obtained hydrogen titanate nanotubes (HTNT), improvements have been achieved, like better charge carriers’ lifetime and lower series resistance. In order to study this system, we carried out previous DFT simulations for this lithium titanate nanotubes through different model's complexity levels which were able to correctly predict its properties. Due to the improvements achieved this system would encourage further studies with the aim to explore its potential for solar cells applications.     

染料敏化太阳电池介孔薄膜电极的研究进展

介绍了染料敏化太阳电池多孔二氧化钛薄膜电极的结构、工作原理及其制备方法,并进一步阐述了减小电荷复合速率、改进薄膜电极性能、提高器件的光电转化效率的方法,主要涉及多孔二氧化钛薄膜电极的复合、掺杂和表面包覆等表面改性处理技术。指出了基于有序二氧化钛薄膜电极、柔性二氧化钛薄膜电极的染料敏化太阳电池和叠层薄膜结构的太阳电池高效的转化效率和应用方便的特点,并在此基础上展望了未来的研究方向。     

染料敏化纳米薄膜太阳电池的研究进展

太阳电池可以直接将太阳光能转变为电能,是解决世界范围内的能源危机和环境污染的一条重要途径。染料敏化纳米薄膜太阳电池具有廉价的原材料和简单的制作工艺以及稳定的性能等优势,是一种很有发展前途的太阳电池。本文对这种电池的发展,特点及其染料敏化剂的研究进展进行了分析和总结。     

Enhanced electrochemical performance of the counterelectrode of dye sensitized solar cells by sandblasting

Counterelectrode plays an important role in dye sensitized solar cells. It helps the regeneration of the redox couples in electrolyte and makes the cell a complete circuit. In order to improve the electrochemical performance of counterelectrode, a strategy of sandblasting has been utilized to pre-treat the surface of glass substrate. Counterelectrodes were fabricated by sputtering Pt/Ti bilayers films onto the treated substrates. Morphological, electrical, electrochemical and optical properties of the counterelectrode were characterized by scanning electronic microscopy, four-probe measurement, electrochemical impedance spectroscopy, cyclic voltammetry and UV-vis reflection spectroscopy, respectively. Effect of the treatment on these properties was evaluated. It was found that counterelectrode made from sandblasted substrates showed increased roughness of surface and sheet resistance, along with the enhanced catalysis efficiency and improved light scattering. The enhanced catalysis efficiency toward reduction of tri-iodide was found to be due to smaller Pt crystallite grown on the sandblasted substrate, since the electrochemical active surface area changed little. And scattering was caused by increased roughness of the substrate. Typical solar cells were assembled with the counterelectrode made of the sandblasted substrates. Effect of the treatment on current-voltage curves and performance parameters of the solar cells was checked and discussed.     

Graphene supported nickel nanoparticle as a viable replacement for platinum in dye sensitized solar cells

A platinum free counter electrode for dye sensitized solar cells was developed using graphene platelets (GP) supported nickel nanoparticles (NPs) as the active catalyst. Few layered GP were prepared by chemical oxidation of graphite powders followed by thermal exfoliation and reduction. The nanoparticles of nickel were deposited directly onto the platelets by pulsed laser ablation. The composite electrodes of GP and Ni nanoparticles (GP-Ni) thus obtained showed better performance compared to conventional Pt thin film electrodes (Std Pt) and unsupported Ni NPs. The efficiencies of the cells fabricated using GP-Ni, Std Pt and Ni NP CEs were 2.19%, 2% and 1.62%, respectively. The GP-Ni composite solar cell operated with an open circuit voltage of 0.7 V and a fill factor of 0.6. Electrochemical impedance spectroscopy using the I(3)(-)/I(-) redox couple confirms lower values of charge transfer resistance for the composite electrodes, 4.67 Ω cm(2) as opposed to 7.73 Ω cm(2) of Std Pt. The better catalytic capability of these composite materials is also reflected in the stronger I(3)(-) reduction peaks in cyclic voltammetry scans.     

Dicationic bis-imidazolium molten salts for efficient dye sensitized solar cells: Synthesis and photovoltaic properties

New dicationic bis-imidazolium salts based ionic liquids were synthesized to develop new electrolytes to improve photovoltaic properties of dye sensitized solar cells. Various properties of electrolytes such as viscosities, ion diffusion coefficients, charge transfer resistances and photovoltaic properties were studied. Electrochemical impedance spectroscopy has been performed to investigate diffusion coefficients and charge transfer resistances. Influence of polarity and chain length on the photovoltaic performance, was investigated. A DSSC employing the K34 (butyl-1,4-bis(3-methyl imidazolium iodide) gives an open-circuit voltage of 0.64 V, a short-circuit current of 17.11 mA/cm² and conversion efficiency of 5.60% under light intensity of 100 mW/cm² while the DSSC based on 1-butyl-3-methyl imidazolium iodide which is a reference ionic liquid exhibited 5.64% efficiency due to the lowest viscosity, highest diffusion coefficient.     

染料敏化纳米晶太阳能电池

本文主要介绍了一种新型的太阳电池———染料敏化纳米晶太阳能电池的结构和基本原理,并详细地阐述了染料敏化纳米晶太阳能电池的研究现状和存在的问题。     

卟啉类有机化合物在染料敏化太阳能电池的应用研究进展

近年来,染料敏化太阳能电池(DSSC)由于低价格、易于制造成大面积、具有较宽的光谱响应范围,可接受的理论转换效率、制造工艺简单、对原料纯度要求不高、寿命长、对环境友好、应用前景广阔等优点而备受关注。染料光敏剂是DSSC的核心材料之一,其性能的优劣将对DSSC光电转化效率起着决定性的作用。介绍了DSSC的基本构造和光电原理,综述了作为光敏化剂的各种卟啉类有机化合物在染料敏化纳米晶太阳能电池中的应用。     

酞菁类染料在敏化太阳能电池中的研究进展

介绍了酞菁的发展及其结构。综述了太阳能电池的研究进展,重点阐述了酞菁化合物在染料敏化太阳能电池中的应用以及几种酞菁类染料敏化剂。     

Reaction induced multifunctional TiO2 rod/particle nanostructured materials for screen printed dye sensitized solar cells

This study investigates the potential of utilizing multifunctional nanostructured materials for the efficient light trapping and electron transport in solar cells by combining titanium dioxide (TiO₂) rods and nanoparticles. A simple solvothermal method was adopted for the synthesis of coupled morphology adopting the desired precursor with the constant concentration and temperature. The reaction duration (12, 24, 36 and 48 h) was varied and the materials resultant physical, optical and structural characteristics were elucidated to determine the nature of the prepared material. The crystallographic phase of the synthesized samples was determined with XRD and Raman analysis. From the experimental data it is hypothesized that the surface plane of anatase (105) is involved in the deformation of the structure and the formation of the rutile phase. To further investigate on the formation of mixed phase in the prepared sample a computation study was performed using density functional theory coupled to the Hubbard U correction (DFT + U) as a function of volume in both the anatase and rutile phases. The relative stability of the O–Ti–O networks is explored starting from ultrathin materials for four different sizes, of anatase and rutile nanorods separately. Finally, the synthesized TiO₂ materials were used to prepare screen printed dye sensitized solar cell (DSSC) devices and their respective properties were quantified.     

Effect of carbonaceous counter electrodes on the performance of ZnO-graphene nanocomposites based dye sensitized solar cells

With many advantages like low-cost preparation, excellent electrical properties, and high catalytic activity; carbon allotropes are the most expected carbon materials to substitute the expensive Platinum (Pt) as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). In the present study, the photovoltaic behaviors of DSSCs fabricated with graphene, multiwalled carbon nanotubes (MWCNTs), and Pt films CEs, respectively, were compared. The graphene and MWCNTs CEs films were prepared by doctor blading the graphene and MWCNTs pastes on Indium tin oxides (ITOs) glass substrates. The structural, morphological, and compositional properties of these carbon CEs viz. graphene and MWCNTs were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX), respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed for the examination of electrochemical and catalytic properties of Pt as well as carbonaceous CEs. These low-cost graphene and MWCNTs CEs were employed in the sandwich-structured DSSCs having ZnO-graphene nanocomposite films as photoanodes. The photoconversion efficiency (η) values of as prepared DSSCs were measured under AM 1.5 illumination (100?mW?cm^?2). The DSSCs with graphene CE and MWCNTs CE performed with efficiency values of 2.26% and 2.04%, respectively. The performance of these carbonaceous CEs are comparative to that of Pt CE which indicates the practicability of carbon based nanomaterials in DSSCs as low cost alternatives to the expensive Pt.     

Iodine-free organic dye sensitized solar cells with in situ polymerized hole transporting material from alkoxy-substituted TriEDOT

An alkoxy-substituted ethylenedioxythiophene (EDOT) trimer is designed and synthesized which has shown a low oxidation potential of 0.50 V versus saturated calomel electrode (SCE). In situ polymerization of the trimer in a thin layer electrolytic cell using organic dye adsorbed on TiO₂ as the working electrode yielded alkoxy-substituted poly(ethylenedioxythiophene) (PEDOT). With D149 as the dye sensitizer and the in situ polymerized polymer as hole-transporting material (HTM), dye sensitized solar cells (DSSCs) were fabricated to show a typical power conversion efficiency of 3.97% under AM 1.5 G (100 mW cm⁻²) illumination. The results show good promise of in situ polymerized conjugated polymers as HTM for iodine/iodide redox-free DSSC applications.     

The photovoltaic efficiencies on dye sensitized solar cells assembled with nanoporous carbon/TiO2 composites

This study examined the characterization of nanoporous structured carbon/TiO₂ composites and its application to dye-sensitized solar cells. TEM of nanoporous structured carbon revealed nanopore sizes of 2.0–3.0 nm with a regular hexagonal form. When nanoporous structured carbon was mixed to TiO₂ particles and then was applied to DSSC, the energy conversion efficiency was enhanced considerably compared with that using only nanometer sized pure TiO₂: the energy conversion efficiency of the DSSC prepared from nanoporous carbon/TiO₂ composites was approximately 3.38%, compared to 2.49% using pure TiO₂. We confirmed from FT-IR spectroscopy that the dye molecules were attached perfectly to the surface and more was absorbed on the nanoporous structured carbon/TiO₂ composite than on the pure TiO₂ particles. In impedance measurements, R₃ which means the Nernstian diffusion within the electrolytes was largely decreased in a cell assembled by nanoporous carbon/TiO₂ composites than that of TiO₂.     

Synthesis and characterization of Co and Ga co-doped ZnO thin films as an electrode for dye sensitized solar cells

Using a time efficient and cost effective approach so called sol‒gel dip coating route, we deposited thin films of ZnO and 1% Co & (0%, 0.5%, 1%, and 1.5%) Ga co-doped ZnO on the fluorine doped tin oxide substrates. All the films exhibited hexagonal wurtzite structure. X-rays study revealed that crystallite size increased with increase of doping. Optical parameters like absorbance, transmittance, refractive index, band gap, extinction coefficient and dielectric constants were measured using UV–Vis spectroscopy and it has been noticed that doping resulted in reduction of band gap. It has also been observed that, the films prepared with 1% Co & 1% Ga co-doped ZnO have comparatively smaller band gap and thus have high refractive index and high transmittance in visible region. The calculation of different electrically important factors for instance, high current density, small open circuit voltage, efficiency and fill factor revealed that co-doped ZnO with 1% Co and 1% Ga has relatively high efficiency of 2.43% and thus shows the potential of this composition as an electrode for solar cell devices.     

Power conversion efficiency enhancement based on the bio-inspired hierarchical antireflection layer in dye sensitized solar cells

We have investigated the effects of the introduction of an antireflection layer consisting of a hierarchically patterned diffraction grating into a conventional TiO(2) working electrode on the power conversion efficiency (PCE) of a DSSC. High index-contrast TiO(2) nanowires (NWs) were grown in the circular holes of the two-dimensional diffraction grating prepared through the use of a polymer template fabricated via interference lithography (IL) for maximized photon trapping effects in the visible region of light. The larger scale dimension of the polymer template was determined using the beam parameters of the IL and the smaller scale dimension in the structures was controlled by the growth conditions of the TiO(2) NWs. Compared with a conventional DSSC, the hybrid nanostructure with an additional antireflection layer demonstrated higher and wider absorption bands of wavelength spectra, leading to an increased PCE due to enhanced light trapping effects achieved by the combination of antireflection and diffraction of the light on the front surface of the devices with minimum loss in the surface area of the hierarchical structure. The excellent performance of the optimized hybrid nanostructure indicates that the nanophotonic effects have strong potential for solar energy conversion, photocatalyst, and photoelectrode applications.