Fabrication of screen‐printing pastes from TiO2 powders for dye‐sensitised solar cells

A preparation technique of TiO₂ screen‐printing pastes from commercially‐available powders has been disclosed in order to fabricate the nanocrystalline layers without cracking and peeling‐off over 17 µm thickness for the photoactive electrodes of the dye‐sensitised solar cells. A conversion efficiency of 8·7% was obtained by using a single‐layer of a semi‐transparent‐TiO₂ film. A conversion efficiency of 9·2% was obtained by using double‐layers composed of transparent and light‐scattering TiO₂ films for a photon‐trapping system. Copyright © 2007 John Wiley & Sons, Ltd.     

Succinonitrile‐based solid‐state electrolytes for dye‐sensitised solar cells

Succinonitrile (SCN), a solid ion conductor (10⁻⁴ to 10⁻³ S/cm) in solid form at room temperature, is mixed with either 1,2‐dimethyl‐3‐propylimidazoliuum iodide or 1‐butyl‐3‐methyl imidazolium iodide ionic liquids for forming a solid plastic phase electrolyte for use in dye‐sensitised solar cell (DSSC). Cells containing these two electrolytes showed best energy conversion efficiencies of 6.3% and 5.6%, respectively. The commonly used DSSC electrolyte additives inhibit the formation of the SCN plastic phase. However, for the first time, an SCN‐additive (additive = guanidinium thiocyanate) electrolyte composition is reported here, which remains as a solid at room temperatures. By using these new solid electrolytes, a simple and rapid single‐step filling procedure for making solid‐state DSSC is outlined. This process, which reduces the required manufacturing steps from four to one, is most suitable for continuous, high‐throughput, commercial DSSC manufacturing lines. These new electrolytes have been tested under low incident light levels (200 lx) to investigate their suitability for indoor DSSC applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Parallel‐connected monolithic dye‐sensitised solar modules

Light‐soaking and high‐temperature storage testing of monolithic dye‐sensitised solar modules with total area module efficiencies above 5% have been performed. Our experiences from the development of a four‐layer monolithic dye‐sensitised solar test cell for comparative testing of material components for dye‐sensitised solar cells have directed our module development to a novel device design consisting of parallel‐connection of individual monolithic cells. The results from the accelerated testing of the modules (total area of 17.0 cm²) with four parallel‐connected cells (active area of 3.38 cm²/cell) are equivalent to those obtained for the monolithic single test cells when using identical device components. The successful transfer from cell to module stability is an important milestone in our ambition to develop a low‐cost Photovoltaic (PV) technology. Moreover, our results indicate that intensified research and development to define the procedures for relevant accelerated testing of dye‐sensitised solar modules is urgently required. Copyright © 2010 John Wiley & Sons, Ltd.     

Electroluminescence as a spatial characterisation technique for dye‐sensitised solar cells

In this study, electroluminescence as a spatial characterisation technique is used to characterise a 6.9% efficient dye‐sensitised solar cell. The obtained image is compared with a light beam‐induced current scan image and a transmittance image. Results reveal the presence of inhomogeneities including those resulting from the topography of the cell and from defects, for example, presence of iodine crystals in the electrolyte, localised absence of dye in the active layer and poor adhesion of the active layer to the electrodes. The ability to identify such inhomogeneities within a relatively short acquisition time gives electroluminescence an advantage over the light beam‐induced current technique. Copyright © 2012 John Wiley & Sons, Ltd.     

Rapid radiative platinisation for dye‐sensitised solar cell counter electrodes

The successful transition of dye‐sensitised solar cell (DSC) manufacture from laboratory to factory requires new thinking in terms of lowering cost and removing time consuming manufacturing process. Platinisation of the fluorine doped tin oxide (FTO) glass counter electrode is essential for the operation of a conventional DSC and is usually carried out by thermal decomposition of chloroplatinic acid at 385 °C for 30 min. Here, near infrared radiation is used to directly heat the FTO layer resulting in full platinisation in 12.5 s. These platinised electrodes behave identically to those produced via conventional static thermal treatment in assembled DSC devices. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly transparent and conducting zinc oxide films deposited by activated reactive evaporation

Highly transparent and conducting undoped zinc oxide films have been obtained with a best resistivity of ～1.1 × 10^-3 Ω cm, a carrier density of ～1.5 × 10²⁰ cm^?3 and a mobility of ～38 cm²V^{?1s ?1}. These were produced by activated reactive evaporation at a deposition rate of 2 to 8Å/s with a substrate temperature ≤200° C. The films deposited by this process were found to have resistivities that were thickness independent and also were relatively insensitive to deposition parameters. In terms of conductivity, it was found that films deposited at higher temperatures (T > 300°+ C) were always inferior to the films deposited below 200° C. High temperature vacuum annealing (350° C) significantly degraded the resistivity of the undoped films deposited at low temperature; this was attributable to a drop in both the electron concentration and the mobility. Aluminum doping was found to be able to stabilize the electron concentration while the drop in mobility was found to be related to the choice of substrate.     

射频磁控溅射法制备掺锆氧化锌透明导电薄膜

利用射频磁控溅射法在室温下制备出了掺锆氧化锌(ZnO∶Zr)透明导电薄膜。研究了溅射压强对ZnO∶Zr薄膜表面形貌、结构、光学和电学性能的影响。结果表明:ZnO∶Zr薄膜为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向,溅射压强对薄膜电阻率有显著影响,压强为1.5Pa时,电阻率具有最小值1.77×10–3Ω·cm。所制备的ZnO∶Zr薄膜具有良好的附着性能,在可见光区平均透过率超过93%。     

Additional coating effects on textured ZnO : Al thin films as transparent conducting oxides for thin‐film Si solar cells

ZnO : Al films were additionally deposited on textured transparent conducting oxide thin films to improve the surface morphologies formed in the etching process. The efficiency of the µc‐Si : H cell was enhanced from 7.0% (uncoated) to 8.0% (150‐nm‐coated) because of the additional coating. The quantum efficiency evaluation with a reverse bias voltage showed that the additional coating suppressed the carrier recombination problem. To systematically analyze the change of the i‐layer quality, the changes of (μτ)_eff and fill factor (FF) were analyzed using a variable illumination measurement technique, and the results clearly confirmed the enhancement of i‐layer quality due to the additional coating. Copyright © 2011 John Wiley & Sons, Ltd.     

Improved conversion efficiency of a‐Si:H/µc‐Si:H thin‐film solar cells by using annealed Al‐doped zinc oxide as front electrode material

In recent years, zinc oxide has been investigated as a front electrode material in hydrogenated amorphous silicon/hydrogenated microcrystalline silicon (a‐Si:H/µc‐Si:H) tandem solar cells. Such as for other transparent conducting oxide materials and applications, a proper balancing of transparency and conductivity is necessary. The latter is directly related to the density and the mobility of charge carriers. A high density of charge carriers increases conductivity but leads to a higher absorption of light in the near‐infrared part of the spectrum due to increased free‐carrier absorption. Hence, the only way to achieve high conductivity while keeping the transparency as high as possible relies on an increase of carrier mobility. The carrier density and the mobility of sputtered Al‐doped zinc oxide (ZnO:Al) can be tailored by a sequence of different annealing steps. In this work, we implemented such annealed ZnO:Al films as a front electrode in a‐Si:H/µc‐Si:H tandem solar cells and compared the results with those of reference cells grown on as‐deposited ZnO:Al. We observed an improvement of short‐circuit current density as well as open‐circuit voltage and fill factor. The gain in current density could be attributed to a reduction of both sub‐band‐gap absorption and free‐carrier absorption in the ZnO:Al. The higher open‐circuit voltage and fill factor are indicators of a better device quality of the silicon for cells grown on annealed ZnO:Al. Altogether, the annealing led to an improved initial conversion efficiency of 12.1%, which was a gain of +0.7% in absolute terms. Copyright © 2013 John Wiley & Sons, Ltd.     

Cold isostatic pressing technique for producing highly efficient flexible dye‐sensitised solar cells on plastic substrates

One of the biggest challenges for making dye‐sensitised solar cells (DSCs) on plastic substrates is the difficulty in making good quality nanoporous TiO₂ films with both good mechanical stability and high electrical conductivity. Cold isostatic pressing (CIP) is a powder compaction technique that applies an isostatic pressure to a powder sample in all directions. It is particularly suitable for making thin films on plastic substrates, including non‐flat surfaces. Cold isostatically pressed nanocrystalline TiO₂ electrodes with excellent mechanical robustness were prepared on indium tin oxide (ITO)‐coated polyethylene naphthalate (PEN) substrates in the absence of organic binders and without heat treatment. The morphology and the physical properties of the TiO₂ films prepared by the CIP method were found to be very compatible with requirements for flexible DSCs on plastics. This room‐temperature processing technique has led to an important technical breakthrough in producing high efficiency flexible DSCs. Devices fabricated on ITO/PEN films by this method using standard P‐25 TiO₂ films with a Ru‐complex sensitiser yielded a maximum incident photon‐to‐current conversion efficiency of 72% at the wavelength of 530 nm and showed high conversion efficiencies of 6.3% and 7.4% for incident light intensities of 100 and 15 mW cm⁻², respectively, which are the highest power conversion efficiencies achieved so far for any DSC on a polymer substrate using the widely used, commercially available P‐25 TiO₂ powder. Copyright © 2011 John Wiley & Sons, Ltd.     

ZnO∶Ti透明导电薄膜的制备与光电性能研究

采用直流磁控溅射法,在水冷7059玻璃衬底上制备了具有高透射率和相对低电阻率的掺钛氧化锌(ZnO∶Ti)透明导电薄膜,研究了溅射偏压对ZnO∶Ti薄膜结构、形貌和光电性能的影响。结果表明,ZnO∶Ti薄膜为六角纤锌矿多晶结构,具有c轴择优取向。溅射偏压对ZnO∶Ti薄膜的结构和电阻率有重要影响。当溅射偏压为10V时,电阻率具有最小值1.90×10–4?.cm。薄膜具有良好的附着性能,可见光区平均透射率超过90%。该ZnO∶Ti薄膜可以用作薄膜太阳能电池和液晶显示器的透明电极。     

Low‐temperature flexible Ti/TiO2 photoanode for dye‐sensitized solar cells with binder‐free TiO2 paste

An energy‐economical dye‐sensitized solar cell (DSSC) with highly flexible Ti/TiO₂ photoanode was developed through a low‐temperature process, using a binder‐free TiO₂ paste. Ti foils, coated with the binder‐free TiO₂ films were annealed at various temperature. Scanning electron microscopic (SEM) images of the films show uniform, mesoporous and crack‐free surface morphologies as well as interpenetrated TiO₂ network. DSSCs with binder‐free TiO₂ films annealed at 450, 350, 250 and 120°C show solar‐to‐electricity conversion efficiencies (η) of 4.33, 4.34, 3.72 and 3.40%, respectively, which are comparable to the efficiency of 4.56% obtained by using a paste with binder and annealing it at 450°C; this observation demonstrates the benefits of a binder‐free TiO₂ paste for the fabrication of energy‐fugal DSSCs. On the other hand, when organic binder was used in the TiO₂ paste for film preparation, a drastic deterioration in the cell performance with decreasing annealing temperature is noticed. Laser‐induced photo‐voltage transient technique is used to estimate the electron lifetime in various Ti/TiO₂ films. Electrochemical impedance spectroscopic (EIS) analysis shows that the lower the annealing temperature of the TiO₂ coated Ti foil, the larger the charge transfer resistance at the TiO₂/dye/electrolyte interface (R_ct2). Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of the distance between target and substrate on the properties of transparent conducting Al-Zr co-doped zinc oxide thin films

Highly transparent and conducting AI-Zr co-doped zinc oxide (ZAZO) thin films were successfully prepared on glass substrate by direct current (DC) magnetron sputtering at room temperature. The distance between target and substrate was varied from 45 to 70 mm. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 70 to 50 mm. However, as the distance decreases further, the crystallinity decreases and the electrical resistivity increases. When the distance between target and substrate is 50 mm, it is found that the lowest resistivity is 6.9×10~(-4) Ω·cm.All the deposited films show a high average transmittance of above 92% in the visible range.     

Influence of the distance between target and substrate on the properties of transparent conducting AI-Zr co-doped zinc oxide thin films

Highly transparent and conducting Al-Zr co-doped zinc oxide （ZAZO） thin films were successfully prepared on glass substrate by direct current （DC） magnetron sputtering at room temperature. The distance between target and substrate was varied from 45 to 70 mm. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 70 to 50 mm. However, as the distance decreases further, the crystallinity decreases and the electrical resistivity increases. When the distance between target and substrate is 50 ram, it is found that the lowest resistivity is 6.9 × 10^-4Ω cm. All the deposited films show a high average transmittance of above 92% in the visible range.     

Influence of the distance between target and substrate on the properties of transparent conducting Al-Zr co-doped zinc oxide thin films

Highly transparent and conducting Al-Zr co-doped zinc oxide (ZAZO) thin films were successfully prepared on glass substrate by direct current (DC) magnetron sputtering at room temperature.The distance between target and substrate was varied from 45 to 70 mm.All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate.The crystallinity increases obviously and the electrical resistivity decreases when the distance betwe...     

低电阻率高透过率TAZO透明导电膜的制备及性能

利用直流磁控溅射工艺,在水冷玻璃衬底上制备了透过率高、电阻率相对较低的钛铝共掺杂ZnO(TAZO)透明导电膜。用XRD和SEM等研究其结构、应力和光电性能与靶基距之间的关系。结果表明:TAZO薄膜为六方纤锌矿结构的多晶薄膜,且具有c轴择优取向。当靶基距为42mm时,薄膜样品晶格畸变最小,具有最小压应力(绝对值)0.270GPa,同时具有最小方块电阻4.21?/□;靶基距为48mm时,薄膜样品具有最小电阻率3.09×10–4?·cm。所有薄膜样品的可见光区平均透过率都超过了91%。     

The use of Ti meshes with self‐organized TiO2 nanotubes as photoanodes of all‐Ti dye‐sensitized solar cells

This paper reports a simple and facile method for directly growing self‐organized TiO₂ nanotubular arrays around the whole Ti mesh by electrochemical anodization in organic electrolytes and their application in all‐Ti dye‐sensitized solar cells (DSSCs). Compared with the traditional fluorine‐doped tin oxide (FTO)‐based DSSC and the backside illuminated DSSC, this type of DSSC showed advantages such as low resistance, cheap fabrication cost and enhanced sunlight utilization. Different thicknesses of nanotubular array layers were investigated to find their influence on the photovoltaic parameters of the cell. We also considered three types of meshes as the substrates of anodes and found that the cell with 6 openings/mm² exhibited the highest conversion efficiency of 5.3%. The area of the cell had only a little impact on the photovoltaic performances. Copyright © 2010 John Wiley & Sons, Ltd.     

溅射压强对磁控溅射法制备的ZnO:Zr透明导电薄膜性能的影响

Transparent conducting zirconium-doped zinc oxide films with high transparency and relatively low resistivity have been successfully prepared on water-cooled glass substrate by radio frequency magnetron sputtering at room temperature. The Ar sputtering pressure was varied from 0.5 to 3 Pa. The crystallinity increases and the electrical resistivity decreases when the sputtering pressure increases from 0.5 to 2.5 Pa. The cystallinity decreases and the electrical resistivity increases when the sputtering pressure increases from 2.5 to 3 Pa. When the sputtering pressure is 2.5 Pa, it is obtained that the lowest resistivity is 2.03 x 10^-3Ω .cm with a very high transmittance of above 94%. The deposited films are polycrystalline with a hexagonal structure and a preferred orientation perpendicular to the substrate.     

Influence of the sputtering pressure on the properties of transparent conducting zirconium-doped zinc oxide films prepared by RF magnetron sputtering

Transparent conducting zirconium-doped zinc oxide films with high transparency and relatively low re-sistivity have been successfully prepared on water-cooled glass substrate by radio frequency magnetron sputtering at room temperature. The Ar sputtering pressure was varied from 0.5 to 3 Pa. The crystallinity increases and the electri-cal resistivity decreases when the sputtering pressure increases from 0.5 to 2.5 Pa. The cystallinity decreases and the electrical resistivity increases when the sputtering pressure increases from 2.5 to 3 Pa. When the sputtering pressure The deposited films are polycrystalline with a hexagonal structure and a preferred orientation perpendicular to the substrate.     

绒面AZO最新研究进展及应用

掺铝氧化锌(AZO)透明导电膜作为一种光电性能优异的透明导电膜(TCO)受到研究人员的广泛关注,并被认为是当前大规模使用的传统铟锡氧化物(ITO)的替换材料。绒面AZO薄膜因其电阻率低、高透过率且具有良好的陷光效果,可以提高太阳能电池的光电转换效率,而被认为是太阳能电池前电极的理想材料。综述了绒面AZO透明导电膜的制备方法和性能研究现状,并针对AZO的国内外研究状况提出了今后的发展趋势和研究方向。