Nanostructured TiO<Subscript>2</Subscript> Films with a Mixed Phase for Perovskite Solar Cells

A series of thin films made with TiO₂ nanoparticles with a varied anatase/rutile phase ratio is prepared on conducting glass substrates using a spin-coating method. The structure, morphology, and optical properties of TiO₂ nanopowders and thin films fabricated are studied using powder X-ray diffraction, scanning electron microscopy, and optical spectroscopy. The TiO₂ nanostructured films created are used as photoelectrodes for the fabrication of perovskite solar cells (PSCs). The photovoltaic characteristics of PSCs under AM1.5 light illumination (1000 W/m²) under ambient conditions are studied. It is shown that the best efficiency of solar-to-electrical energy conversion, namely, 9.3%, is obtained for the PSC with a photoelectrode based on a TiO₂ film with an anatase/rutile mixed phase ratio of 86/14%.     

The hybrid photocatalyst of TiO2–SiO2 thin film prepared from rice husk silica

The TiO₂–SiO₂ thin film was prepared by self-assembly method by mixing SiO₂ precursor with titanium precursor solution and aged to obtain a co-precipitation of silica and titanium crystals. Dip coating method was applied for thin film preparation on glass slide. The X-ray diffraction (XRD) of the self-assembly thin film had no characteristic property of SiO₂ and even anatase TiO₂ but indicated new crystal structure which was determined from the Fourier Transform Infrared Spectrophotometer (FTIR) as a hybridized Ti–O–Si bonding. The surface area and surface volume of the self-assembly sample were increased when SiO₂ was incorporated into the film. The self-assembly TiO₂–SiO₂ thin film exhibited the enhanced photocatalytic decolorization of methylene blue (MB) dye. The advantages of SiO₂ are; (1) to increase the adsorbability of the film and (2) to provide the hydroxyl radical to promote the photocatalytic reaction. The self-assembly thin film with the optimum molar ratio (SiO₂:TiO₂) as 20:80 gave the best performance for photocatalytic decolorization of MB dye with the overall efficiency of 81%.     

Fabrication and characterization of CdS-sensitized TiO<Subscript>2</Subscript> nanotube photoelectrode

CdS quantum dot (Qd)-sensitized TiO₂ nanotube array photoelectrode is synthesised via a two-step method on tin-doped In₂O₃-coated (ITO) glass substrate. TiO₂ nanotube arrays are prepared in the ethylene glycol electrolyte solution by anodizing titanium films which are deposited on ITO glass substrate by radio frequency sputtering. Then, the CdS Qds are deposited on the nanotubes by successive ionic layer adsorption and reaction technique. The resulting nanotube arrays are characterized by scanning electron microscopy, X-ray diffraction (XRD) and UV–visible absorption spectroscopy. The length of the obtained nanotubes reaches 1.60 μm and their inner diameter and wall thickness are around 90 and 20 nm, respectively. The XRD results show that the as-prepared TiO₂ nanotubes array is amorphous, which are converted to anatase TiO₂ after annealed at 450 °C for 2 h. The CdS Qds deposited on the TiO₂ nanotubes shift the absorption edge of TiO₂ from 388 to 494 nm. The results show that the CdS-sensitized TiO₂ nanotubes array film can be used as the photoelectrode for solar cells.     

电沉积处理与染料敏化纳米薄膜太阳电池的优化

采用阳极氧化水解法对染料敏化纳米TiO₂薄膜太阳电池的光阳极进行不同方式的电沉积优化处理.借助x射线衍射仪对处理后的样品进行分析，通过超高分辨率场发射扫描电子显微镜对导电玻璃以及电沉积处理前后纳米多孔薄膜表面进行了粒径和形貌的扫描.染料敏化太阳电池实验测试结果表明，电沉积处理和修饰后可以明显提高光生电子的收集率，增大短路电流密度，提高电池效率. 关键词： 2')" href="#">纳米TiO₂ 染料敏化 电沉积 太阳电池     

Effects of 1064 nm laser on the structural and optical properties of nanostructured TiO2 thin film

TiO₂ thin film has been widely used as photoelectrode in dye-sensitized solar cells. It can also be used in quantum dot synthesized solar cells. Study of its effects in different spectrum of light is important for its use in solar cells. We have reported effects of 1064 nm laser on the surface morphology, structural and optical properties of nanostructured TiO₂ thin film deposited on glass substrates using sol-gel spin coating technique. Q-Switched Nd:YAG pulsed laser at various power densities is used in this study. Surface morphology of the film is investigated using X-ray diffraction (XRD) and atomic force microscopy technique. The XRD pattern of as deposited TiO₂ thin film is amorphous and after laser exposure it became TiO₂ anatase structure. Atomic force microscopy of the crystalline TiO₂ thin film shows that the grain size increases by increasing laser power density. The calculations of the band gap are carried out from UV/Visible spectroscopy measurements with JASCO spectrometer. For laser power density of 25 MW/cm² there is an increase in the transmission and it decreases at the value of 38 MW/cm² and band gap decreases with increasing laser power density. Photoluminescence spectra of the crystalline TiO₂ thin film indicate two broad peaks in the range of 415 and 463 nm, one for band gap peak (415 nm) and other for oxygen defect during film deposition process.     

Material properties controlling photocurrent on TiO2 aggregates with plane orientation for dye-sensitized solar cells

Effective design of a dye-sensitized solar cell (DSSC) requires a clear understanding of the reaction mechanisms of the constituent cell materials. The relationship between structural and photo-electrochemical properties of the photo-anodic materials is of the first priority for such investigations. Highly oriented aggregates of anatase phase TiO₂ nanoparticles were deposited on Indium Tin oxide (ITO) glass substrates; over which N719 dyes were adsorbed through electrophoretic deposition under a strong magnetic field. The properties were evaluated by electrochemical measurements, UV–VIS spectroscopy, and electrical resistance measurements. The results showed that the absorbed photon number in the TiO₂ aggregates with adsorbed dye and their resistivity showed different dependences on the orientation of the crystal plane in the TiO₂ particle. The dependence of the photocurrent on the plane orientation of aggregates of dye-sensitized TiO₂ nanoparticles has been determined from a combination of the electrical conductivity of TiO₂ aggregate and the amount of dye adsorbed on the surface of TiO₂.     

Cocktail effect of Fe2O3 and TiO2 semiconductors for a high performance dye-sensitized solar cell

The bi-semiconductors of TiO₂ and Fe₂O₃ were used as a photoelectrode material in a high performance dye-sensitized solar cell due to cocktail effects from the two conduction bands. The size of the semiconductors was reduced by using a paint shaker to enlarge the contact area of the semiconductor with the dye or electrolyte. The fill factor and the efficiency of the prepared dye-sensitized solar cell were improved by over 16% and 300%, respectively; these parameters were measured from a current-voltage curve that was based on the effects of the Fe₂O₃ co-semiconductor and the size reduction. A mechanism is suggested wherein the conduction band of Fe₂O₃ works to prohibit the trapping effects of electrons in the conduction band of TiO₂. This result is attributed to the prevention of electron recombination between electrons in the TiO₂ conduction band with dye or electrolytes. The mechanism is suggested based on impedance results, which indicate improved electron transport at the interface of the TiO₂/dye/electrolyte.     

Preparation and photoelectrochemical performance of Ag/graphene/TiO2 composite film

By dipping-lifting in sol-gel solution and reducing process, the graphene/TiO₂ composite film on the glass plate was first prepared. Then, the Ag/graphene/TiO₂ composite film was fabricated by interface reaction with AgNO₃ and N₂H₄·H₂O on the surface of graphene/TiO₂ composite film. The characterization results show that the uniform porous TiO₂ film is made up of the anatase crystal, and the Ag/graphene/TiO₂ composite film is constructed by doping or depositing graphene sheets and Ag nanoparticles on the surface of TiO₂ film. The photoelectrochemical measurement results indicate that the Ag/graphene/TiO₂ composite film has an excellent photoelectrochemical conversion property.     

Influence of annealing temperature on the photoluminescence property of ZnO thin film covered by TiO2 nanoparticles

In this work, ZnO thin films covered by TiO₂ nanoparticles (labeled as TiO₂-ZnO thin films) were prepared by electron beam evaporation. The influence of annealing temperature on the photoluminescence property of the samples was studied. The structures and surface morphologies of the samples were analyzed by X-ray diffraction (XRD) and atomic force microscope, respectively. The photoluminescence was used to investigate the fluorescent properties of the samples. The measurement results show that the ultraviolet emission of ZnO thin films is largely enhanced after they are covered by TiO₂ nanoparticles, while the green emission is suppressed. However, when the annealing temperature is relatively high (≥500 °C), the intensity of ultraviolet emission drops off and a violet emission peak along with a blue emission peak appears. This is probably connected with the atomic interdiffusion between TiO₂ nanoparticles and ZnO thin film. Therefore, selecting a suitable annealing temperature is a key factor for obtaining the most efficient ultraviolet emission from TiO₂-ZnO thin films.     

一种印刷型薄膜太阳能电池p-n结调制技术

能带值为0.5~0.85 eV材料的稀缺是多结太阳能电池面临的一个主要挑战,本文使用非真空的机械化学法合成了能带值为0.83 eV的Cu₂SnS₃化合物,使用印刷技术将其制备成吸收层薄膜,并采用superstrate太阳能电池结构(Mo/Cu₂SnS₃/In₂S₃/TiO₂/FTO glass)对其光伏特性进行了研究.实验表明所制备的太阳能电池短路电流密度、开路电压、填充因子和转换效率分别为12.38 mA/cm²、320 mV、0.28和1.10%.此外,为更好地满足多结太阳能电池对电流匹配的需求,本文对所制备太阳能电池的Cu₂SnS₃/In₂S₃ p-n结进行了分析.通过在p-n结界面植入一层薄的疏松缓冲层,使调制后的太阳能电池短路电流密度从最初的12.38 mA/cm²增加到了23.15 mA/cm²,相应太阳能电池转换效率从1.1%增加到了1.92%.该p-n调制技术对印刷型薄膜太阳能电池具有重要借鉴意义.     

Controlled synthesis of TiO2-B nanowires and nanoparticles for dye-sensitized solar cells

Controllable synthesis of the TiO₂-B nanowires (NWs) and nanoparticles (NPs) had been achieved via a facile hydrothermal route, respectively, only by tuning the solution volume. The dye-sensitized solar cells prototypes had been fabricated using TiO₂-B NW and NP electrodes, respectively. The TiO₂-B NP cells had higher photocurrent and photoelectrical conversion efficiency than the TiO₂-B NW cells though the latter exhibited larger photovoltage compared to the former. The key factors such as the photogenerated electron injection drive force, surface defects and the interfacial charge transfer, which determined the photoelectrical properties, had been systematically researched with the surface photovoltage spectra (SPS) and the electrochemical impedance spectra (EIS). The SPS proved that there was larger photoelectron injection drive force in TiO₂-B NP photoelectrode than that in NW photoelectrode. And the electrochemical impedance spectra (EIS) revealed that TiO₂-B NP cells had faster interface charge transfer compared to TiO₂-B NW cells. Both proved that NP cells had the higher photocurrents.     

Optical properties of ITO/TiO2 single and double layer thin films deposited by RPLAD

Indium tin oxide (ITO) and titanium dioxide (TiO₂) single layer and double layer ITO/TiO₂ films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser for applications in dye-sensitized solar cells (DSSCs). The films were deposited on SiO₂ substrates either at room temperatures (RT) or heated to 200-400 °C. Under optimized conditions, transmission of ITO films in the visible (vis) range was above 89% for films produced at RT and 93% for the ones deposited at higher temperatures. Increasing the substrate temperature from RT to 400 °C enhances the transmission of TiO₂ films in the vis-NIR from about 70% to 92%. High transmission (≈90%) was observed for the double layer ITO/TiO₂ with a transmission cut-off above 900 nm. From the transmission data, the energies gaps (E_g), as well as the refractive indexes (n) for the films were estimated. n ≈ 2.03 and 2.04, respectively for ITO films and TiO₂ film deposited at 400 °C in the visible region. Post-annealing of the TiO₂ films for 3 h at 300 and 500 °C was performed to enhance n. The refractive index of the TiO₂ films increases with the post-annealing temperature. The direct band gap is 3.6, 3.74 and 3.82 eV for ITO films deposited at RT, 200, and 400 °C, respectively. The TiO₂ films present a direct band gap of 3.51 and 3.37 eV for as deposited TiO₂ films and when annealed at 400 °C, respectively. There is a shift of about 0.1 eV between ITO and ITO/TiO₂ films deposited at 200 °C. The shift decreases by half when the TiO₂ film was deposited at 400 °C. Post-annealing was also performed on double layer ITO/TiO₂.     

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.     

锐钛矿相TiO2纳米管的制备及其染料敏化太阳电池

以商用金红石相TiO₂粉末为原料,通过在碱性溶液中150℃水热48h的方法合成TiO₂纳米管.采用SEM,TEM,XRD分析手段对TiO₂纳米管的形貌和结构演变进行了表征.制成的TiO₂纳米管与TritonX-100,乙酰丙酮混合后,通过丝网印刷的方法涂敷到ITO导电玻璃衬底上,并且在450℃下烧结30min后得到可应用于染料敏化太阳电池的多孔光阳极.将此光阳极浸泡于N719染料敏化后,与镀铂对电极组装电池,两者之间灌 关键词： 2纳米管')" href="#">TiO₂纳米管 染料敏化太阳电池 水热法     

Growth of ultra-thin TiO2 films by spray pyrolysis on different substrates

In the present study TiO₂ films were deposited by spray pyrolysis method onto ITO covered glass and Si (1 0 0) substrates. The spray solution containing titanium(IV) isopropoxide, acetylacetone and ethanol was sprayed at a substrate temperature of 450 °C employing 1-125 spray pulses (1 s spray and 30 s pause). According to AFM, continuous coverage of ITO and Si substrates with TiO₂ layer is formed by 5-10 and below 5 spray pulses, respectively. XPS studies revealed that TiO₂ film growth on Si substrate using up to 4 spray pulses follows 2D or layer-by-layer-growth. Above 4 spray pulses, 3D or island growth becomes dominant irrespective of the substrate. Only 50 spray pulses result in TiO₂ layer with the thickness more than XPS measurement escape depth as any signal from the substrate could not be detected. TiO₂ grain size remains 30 nm on ITO and increases from 10-20 nm to 50-100 nm on Si substrate with the number of spray pulses from 1 to 125.     

Photosensitization of nanocrystalline TiO2 film electrode with cadmium sulphoselenide

Nanocrystalline titanium dioxide (TiO₂) thin films composed of densely packed nanometer-sized grains have been successfully deposited onto an indium-doped-tin oxide (ITO) substrate. Then cadmium sulphoselenide (CdSSe) thin film was deposited onto pre-deposited TiO₂ to form a TiO₂/CdSSe film, at low temperature using a simple and inexpensive chemical method. The X-ray diffraction, selected area electron diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and water contact angle techniques were used for film characterization. Purely rutile phase of TiO₂ with super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 30-40 (±2) nm was observed. The increase in optical absorption was observed after CdSSe film deposition. Nest like surface morphology of CdSSe on TiO₂ surface results in air trapping in the crevices which prevents water from adhering to the film with increase in water contact angle. Photosensitization of TiO₂ with CdSSe was confirmed with light illumination intensity of 80 mW/cm².     

Optical and hydrophilic properties of Cr doped TiO2-SiO2 nanostructure thin film

Cr doped TiO₂-SiO₂ nanostructure thin film on glass substrates was prepared by a sol-gel dip coating process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structural and chemical properties of the films. A UV-vis spectrophotometer was used to measure the transmittance spectra of the thin film. The hydrophilicity of the thin film during irradiation and storage in a dark place was measured by a contact angle analyzer. The results indicated that Cr doping has a significant effect on the transmittance and super-hydrophilicity of TiO₂-SiO₂ thin film.     

The dispersion study of TiO2 nanoparticles surface modified through plasma polymerization

In this study, the surface of TiO₂ nanoparticles was modified through plasma polymerization, which is a dry coating method at room temperature. The surface morphology of TiO₂ nanoparticles was characterized by high-resolution transmission electron microscope (HRTEM). The dispersion behavior of TiO₂ nanoparticles in water and ethyl glycol was investigated by laser size distribution and ultraviolet–visible absorption spectrum. TiO₂ nanoparticles were coated with a thin film through plasma polymerization, which prevents the agglomeration and improves the dispersion behavior of TiO₂ nanoparticles.     

Transparent titania nanotubes of micrometer length prepared by anodization of titanium thin film deposited on ITO

Transparent TiO₂ nanotube arrays of micrometer lengths were prepared by anodization of titanium thin film RF sputtered on indium tin oxide (ITO) which was coated on glass substrate. The sputtering process took place at elevated temperature of 500 °C. The structures of the films were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) while the optical properties of the films were investigated using UV-visible spectroscopy. Two types of electrolytes were used in this work: an aqueous mixture of acetic acid and HF solution and a mixture of NH₄F and water dissolved in ethylene glycol. The concentration of NH₄F, voltage and the thickness of the sputtered titanium film were varied to study their effect on the formation of TiO₂ nanotube arrays. It is demonstrated in this work that the nanoporous layer is formed on top of the ordered array of TiO₂ nanotubes. Furthermore, the optical transmittance of TiO₂ nanotubes annealed at 450 °C is much lower than the non annealed TiO₂ nanotubes in the visible wavelength region.     

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.