Chemically deposited TiO2/CdS bilayer system for photoelectrochemical properties

In the present investigation, TiO₂, CdS and TiO₂/CdS bilayer system have been deposited on the fluorine doped tin oxide (FTO) coated glass substrate by chemical methods. Nanograined TiO₂ was deposited on FTO coated glass substrates by successive ionic layers adsorption and reaction (SILAR) method. Chemical bath deposition (CBD) method was employed to deposit CdS thin film on pre-deposited TiO₂ film. A further study has been made for structural, surface morphological, optical and photoelectrochemical (PEC) properties of FTO/TiO₂, FTO/CdS and FTO/TiO₂/CdS bilayers system. PEC behaviour of FTO/TiO₂/CdS bilayers was studied and compared with FTO/CdS single system. FTO/TiO₂/CdS bilayers system showed improved performance of PEC properties over individual FTO/CdS thin films.     

Computational design of high efficiency FeSi2 thin-film solar cells

A novel PV cell structure in the form of a p-i-n construction is proposed by inserting a layer of FeSi₂ between two layers of crystalline silicon. The energy band diagram and PV properties are simulated. The structure parameters, such as the thickness, doping concentration and defect density of states of each layer, are taken into account. The optimized structure with a thickness less than 1 μm shows a large open circuit voltage (Voc) of 0.68 V and a high photoelectric conversion efficiency (Eff) of 24.7%, which is significantly larger than that of the FeSi₂/Si double-layer pn-heterojunction structure, and is comparable with the performance of crystalline Si solar cells with a thickness of 250 μm. The Voc and Eff increase further when replacing the crystalline Si at both sides of the FeSi₂ layer with amorphous Si layers. The present work is expected to open a new avenue in developing low-cost thin film solar cells on the basis of the well established Si technology.     

Conductivity enhancement of ZnO:F thin films by the deposition of SnO2:F over layers for optoelectronic applications

Fluorine doped tin oxide (SnO₂:F – FTO) layer is deposited over fluorine doped zinc oxide layer (ZnO:F – FZO) so as to get FTO/FZO bilayers with varying thickness proportions of the two layers using a simplified spray pyrolysis technique. In order to analyse the possible enhancement in the transparent conducting properties of these bilayered films, two separate sets of single layered FTO and FZO films are prepared with similar thickness values and their electrical, optical, photoluminescence and structural characteristics are compared with their bilayered counterparts. The electrical studies revealed that the double-layered films with the lesser thickness of FTO exhibit higher sheet resistance (R_sh) and the R_sh value decreases with the increase in the thickness of FTO over layer. The FTO/FZO bilayer with thickness proportions of FTO:FZO nearly equal to 450 nm:300 nm (3:2) is found to have good figure of merit (quality factor) when compared with FZO films. Even though the optical transmittance (T) in the visible range of FTO/FZO bilayer is lesser (80%) than that of FZO (90%) and FTO (85%) films, the electro-optical properties are reasonably good for the bilayered films making them suitable candidates for opto-electronic applications. The photoluminescence studies support the results obtained in the electrical and structural studies.     

3D FTO/FTO‐Nanocrystal/TiO2 Composite Inverse Opal Photoanode for Efficient Photoelectrochemical Water Splitting

A 3D fluorine‐doped SnO₂ (FTO)/FTO‐nanocrystal (NC)/TiO₂ inverse opal (IO) structure is designed and fabricated as a new “host and guest” type of composite photoanode for efficient photoelectrochemical (PEC) water splitting. In this novel photoanode design, the highly conductive and porous FTO/FTO‐NC IO acts as the “host” skeleton, which provides direct pathways for faster electron transport, while the conformally coated TiO₂ layer acts as the “guest” absorber layer. The unique composite IO structure is fabricated through self‐assembly of colloidal spheres template, a hydrothermal method and atomic layer deposition (ALD). Owing to its large surface area and efficient charge collection, the FTO/FTO‐NC/TiO₂ composite IO photoanode shows excellent photocatalytic properties for PEC water splitting. With optimized dimensions of the SnO₂ nanocrystals and the thickness of the ALD TiO₂ absorber layers, the 3D FTO/FTO‐NC/TiO₂ composite IO photoanode yields a photocurrent density of 1.0 mA cm^?2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5 illumination, which is four times higher than that of the FTO/TiO₂ IO reference photoanode.     

Electrical and structural characterization of plasma polymerized polyaniline/TiO2 heterostructure diode: a comparative study of single and bilayer TiO2 thin film electrode

A heterostructure was fabricated using p-type plasma polymerized polyaniline (PANI) and n-type (single and bilayer) titanium dioxide (TiO2) thin film on FTO glass. The deposition of single and bilayer TiO2 thin film on FTO substrate was achieved through doctor blade followed by dip coating technique before subjected to plasma enhanced polymerization. To fabricate p-n heterostructure, a plasma polymerization of aniline was conducted using RF plasma at 13.5 MHz and at the power of 120 W on the single and bilayer TiO2 thin film electrodes. The morphological, optical and the structural characterizations revealed the formation of p-n heterostructures between PANI and TiO2 thin film. The PANI/bilayer TiO2 heterostructure showed the improved current-voltage (I-V) characteristics due to the substantial deposition of PANI molecules into the bilayer TiO2 thin film which provided good conducting pathway and reduced the degree of excitons recombination. The change of linear I-V behavior of PANI/TiO2 heterostructure to non linear behavior with top Pt contact layer confirmed the formation of Schottky contact at the interfaces of Pt layer and PANI/TiO2 thin film layers.     

TiO2\FTO镀膜玻璃色饱和度的数值模拟

本文以具有较高折射率的材料——二氧化钛(TiO2)替代自身折射率较低的材料——SiCOx作为氟掺杂氧化锡(FTO)镀膜玻璃中间层薄膜,通过数值模拟计算的方法主要研究了TiO2\FTO镀膜玻璃的表面色饱和度控制表现,并与传统的SiCOx\FTO镀膜玻璃就色饱和度控制表现进行了对比,结果发现TiO2\FTO镀膜玻璃具有更加优异的表面色饱和度控制表现,适合进行实际应用推广。     

Enhancement of photovoltaic performance in dye-sensitized solar cells with the spin-coated TiO2 blocking layer

The TiO2 thin film layers were introduced with the spin-coating method between FTO electrode and TiO2 photoanode in dye sensitized solar cell (DSSC) to prevent electron back migration from the FTO electrode to electrolyte. The DSSC containg different thickness of TiO2 thin film (10-30, 40-60 and 120-150 nm) were prepared and photovoltaic performances were analysed with /-Vcurves and electrochemical impedance spectroscopy. The maximum cell performance was observed in DSSC with 10-30 nm of TiO2 thin film thickness (11.92 mA/cm2, 0.74 V, 64%, and 5.62%) to compare with that of pristine DSSC (11.09 mA/cm2, 0.65 V, 62%, and 4.43%). The variation of photoelectric conversion efficiency of the DSSCs with different TiO2 thin film thickness was discussed with the analysis of crystallographic and microstructural properties of TiO2 thin films.     

Performance improvement of dye-sensitized solar cells by surface patterning of fluorine-doped tin oxide transparent electrodes

The surface modification of fluorine-doped tin oxide (FTO) transparent electrodes was carried out by lithography and inductively coupled plasma etching to improve the conversion efficiency of dye-sensitized solar cells (DSSCs). The concentration of Cl₂ gas and dc-bias voltage to the substrate were varied as the main etch parameters. The transmittance and sheet resistance of the FTO electrodes were compared before and after etching. The DSSCs fabricated on the patterned FTO electrodes showed higher conversion efficiency than those fabricated on the ordinary FTO electrodes without patterns. Scanning electron microscopy showed that more TiO₂ particles could be involved in the DSSCs with patterned FTO electrodes, and that the contact between the TiO₂ layer and electrode were improved by patterning the FTO electrode. The current-voltage curves and incident photon to current efficiency spectra showed that a significantly higher photocurrent was produced in the DSSCs fabricated on the patterned FTO.     

Periodic FTO IOs/CdS NRs/CdSe Clusters with Superior Light Scattering Ability for Improved Photoelectrochemical Performance

Periodic fluorine‐doped tin oxide inverse opals (FTO IOs) grafted with CdS nanorods (NRs) and CdSe clusters are reported for improved photoelectrochemical (PEC) performance. This hierarchical photoanode is fabricated by a combination of dip‐coating, hydrothermal reaction, and chemical bath deposition. The growth of 1D CdS NRs on the periodic walls of 3D FTO IOs forms a unique 3D/1D hierarchical structure, providing a sizeable specific surface area for the loading of CdSe clusters. Significantly, the periodic FTO IOs enable uniform light scattering while the abundant surrounded CdS NRs induce additional random light scattering, combining to give multiple light scattering within the complete hierarchical structure, significantly improving light‐harvesting of CdS NRs and CdSe clusters. The high electron collection ability of FTO IOs and the CdS/CdSe heterojunction formation also contribute to the enhanced charge transport and separation. Due to the incorporation of these enhancement strategies in one hierarchical structure, FTO IOs/CdS NRs/CdSe clusters present an improved PEC performance. The photocurrent density of FTO IOs/CdS NRs/CdSe clusters at 1.23 V versus reversible hydrogen electrode reaches 9.2 mA cm^?2, which is 1.43 times greater than that of CdS NRs/CdSe clusters and 3.83 times of CdS NRs.     

Comparative study of ITO and FTO thin films grown by spray pyrolysis

Tin doped indium oxide (ITO) and fluorine doped tin oxide (FTO) thin films have been prepared by one step spray pyrolysis. Both film types grown at 400 °C present a single phase, ITO has cubic structure and preferred orientation (4 0 0) while FTO exhibits a tetragonal structure. Scanning electron micrographs showed homogeneous surfaces with average grain size around 257 and 190 nm for ITO and FTO respectively.The optical properties have been studied in several ITO and FTO samples by transmittance and reflectance measurements. The transmittance in the visible zone is higher in ITO than in FTO layers with a comparable thickness, while the reflectance in the infrared zone is higher in FTO in comparison with ITO. The best electrical resistivity values, deduced from optical measurements, were 8 × 10⁻⁴ and 6 × 10⁻⁴ Ω cm for ITO (6% of Sn) and FTO (2.5% of F) respectively. The figure of merit reached a maximum value of 2.15 × 10⁻³ Ω⁻¹ for ITO higher than 0.55 × 10⁻³ Ω⁻¹ for FTO.     

Fabrication of dye-sensitized solar cells using Nb2O5 blocking layer made by sol-gel method

In this study, nanocrystalline Nb2O5 thin film has been prepared via sol-gel process using niobium ethoxide as a precursor. Sol-gel films using various ratios of H2O/Nb have been prepared on fluorinated tin oxide (FTO) glass substrate, and used as electron-blocking layer of dye-sensitized solar cell (DSSC). The Nb2O5 film as deposited was amorphous, but became crystalline with hexagonal phase after heat treatment at 600 degrees C. With higher H2O/Nb molar ratio, denser and more uniform Nb2O5 film surface was obtained. DSSCs with the structure of FTO/Nb2O5/TiO2/Dye/EL/Pt/FTO have been prepared, and their solar-cell performance was evaluated. By introduction of Nb2O5 sol-gel film between FTO and TiO2 layer in DSSCs, energy conversion efficiency could be improved.     

Preparation of fluorine-doped tin oxide (SnO2:F) film on polyethylene terephthalate (PET) substrate

Fluorine-doped tin oxide (FTO), one of the most popular transparent conductive oxide (TCO) materials, coated on glass has been used in various applications including many new-generation solar cells. However, there is a lack of reporting when it comes to FTO coated on flexible transparent substrate. For this paper, spray pyrolysis technique was used to have FTO firstly coated on to a brass substrate, which was then dissolved away after cementing an upper flexible transparent polyethylene terephthalate (PET) substrate, finally leaving high quality FTO film on PET substrate. Their structural, electrical, optical and flexible properties were investigated. The lowest resistivity was 7.6 × 10^− 4 Ω cm, which is as good as conventional FTO deposited on glass. Their fold ability could be significantly improved to transcend commercial ITO/PET only by increasing the pretreating time of the brass substrate.     

N离子注入改性SnO2缓冲层及其CdTe太阳电池应用

使用等离子注入技术对SnO_2薄膜进行N离子注入改性,进行方块电阻、光学透过、表面形貌、Kelvin探针和X射线光电子能谱(XPS)表征,并将其作为缓冲层应用到CdTe太阳电池中。研究结果发现,对于30nm厚的SnO_2缓冲层,经过30s、10min不同时间N离子注入以后,其300~800nm波长范围透过率有所降低,而体电阻率则明显增加,特别是N离子注入10min的SnO_2缓冲层,表面出现很多凹孔,呈蜂窝状结构,且对后续沉积的CdS层表面形貌产生了明显影响。Kelvin探针表征结果显示,随着N离子注入时间的延长,SnO_2缓冲层功函数逐渐增加,最高达到约5.075eV,比本征SnO_2缓冲层的功函数高出0.15eV。XPS测试结果显示,N离子注入10min后,SnO_2缓冲层N1s结合能峰位向低结合能方向发生了明显移动,而O1s结合能峰位则向高结合能方向移动了,且表面区非晶格氧所占比例增大。对比电池结果,有N离子注入改性SnO_2缓冲层的电池与无缓冲层的电池相比,效率从10%左右增加到12%以上,最高达到12.47%,其中开路电压提高最为显著,从约750mV提高到790mV以上,提升了约5%,电池的整体均匀性也明显改善。     

Development of electrodeposited ZnTe layers as window materials in ZnTe/CdTe/CdHgTe multi-layer solar cells

Zinc telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using a low-cost electrodeposition method. The resulting films have been characterized using various techniques in order to optimize growth parameters. X-ray diffraction (XRD) has been used to identify the phases present in the films. Photoelectrochemical (PEC) cell and optical absorption measurements have been performed to determine the electrical conductivity type, and the bandgap of the layers, respectively. It has been confirmed by XRD measurement that the deposited layers mainly consist of ZnTe phases. The PEC measurements indicate that the ZnTe layers are p-type in electrical conduction and optical absorption measurements show that their bandgap is in the range 2.10–2.20 eV. p-Type ZnTe window materials have been used in CdTe based solar cell structures, following new designs of graded bandgap multi-layer solar cells. The structures of FTO/ZnTe/CdTe/metal and FTO/ZnTe/CdTe/CdHgTe/metal have been investigated. The results are presented in this paper using observed experimental data.     

Characterization of transparent conductive ITO, ITiO, and FTO films for application in photoelectrochemical cells

Transparent conductive In(2-x)Sn(x)O3 (ITO) and In(2-x)Ti(x)O3 (ITiO) films were prepared via RF magnetron sputtering on soda-lime glass substrates at 300 degrees C and investigated with respect to their photoelectric conversion performance compared with the commercial F:SnO2 (FTO) glass. The near infrared ray transmittance of ITiO was highest for wavelengths over 1000 nm compared with those of ITO and FTO. Photoelectrochemical cells (PECs) were fabricated using ITiO film, ITO film, and FTO glass. The photoelectric conversion efficiency (eta) of the PECs samples using ITiO was 5.64%, whereas 2.73% was obtained from the PEC samples with ITO, both at 100 mW/cm2 light intensity. The impedance measurement was also used to explain the electrochemical performance of the PECs with various TCO glasses.     

高开孔率染料敏化太阳能电池一体化模块及其性能优化

本实验设计了一种简单有效的一体化大尺度染料敏化太阳能电池(DSC)模块, 开孔率(有效面积与总面积之比)高达85%, 远高于传统的串联和并联模块设计. 该设计采用在光阳极导电玻璃表面电镀镍栅极和对电极导电玻璃表面电镀镍薄膜修饰来降低电池传输电阻. 有效面积为510 mm2的电池模块光电转换效率η达到3.00%(AM 1.5, 100 mW/cm²), 填充因子(FF)为0.594, 与未镀镍的样品(η为0.537%, FF为0.251)相比, 性能显著提高. 并利用阻抗谱对大面积性能改善进行了解释, 还利用SEM、XRD等分析了电镀镍薄膜的质量.     

Fabrication of high-performance fluorine doped-tin oxide film using flame-assisted spray deposition

A high-performance fluorine-doped tin oxide (FTO) film was fabricated by flame-assisted spray deposition method. By varying the NH₄F doping concentration, the optimal concentration was established as 8 at.%. X-ray diffractograms confirmed that the as-grown FTO film was tetragonal SnO₂. In addition, the FTO film was comprised of nano-sized grains ranging from 40 to 50 nm. The heat-treated FTO film exhibited a sheet resistance of 21.8 Ω/? with an average transmittance of 81.9% in the visible region (λ = 400-800 nm). The figures of merit shows that the prepared FTO film can be used for highly efficient dye-sensitized solar cells electrodes.     

Comparison of the dye-sensitized solar cells performances based on transparent conductive ITO and FTO

We investigated dye-sensitized solar cell (DSSC) performances with regard to transparent conducting oxide substrates: indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO). The DSSCs were in a standard configuration: a photoelectrode of TiO₂ nanoparticles (9 nm size, anatase phase) deposited on transparent and electrically conductive substrates, counter electrodes of Pt-coated glass, ruthenium 535 dye, and AN50 iodolyte electrolyte (Solaronix). The cells manufactured from ITO (FTO) had an open circuit voltage of 705 (763) mV and short-circuit current of 7.87 (34.3) mA/cm². A direct correlation was found between transparent conductive film resistivity and cell efficiency. Resistivities of 52 Ω/sq for ITO substrates and 8.5 Ω/sq for FTO led to major differences in internal global efficiency: from 2.24% for ITO to 9.6% for FTO.     

Preparation of indium selenide thin film by electrochemical technique

Indium Selenide (In_xSe_y) layers were potentiostatically deposited on glass/fluorine-doped tin oxide (FTO) substrates, using electro-chemical technique from aqueous solution containing 0.10 M InCl₃ and 0.02 M SeO₂. The electrodeposits were characterised using a wide range of analytical techniques; X-ray diffraction (XRD), scanning electron microscopy (SEM), Atomic force microscopy (AFM), optical absorption and photoelectrochemical (PEC) cell, for their structural, morphological, optical and electrical properties. The XRD show that the prepared films consist of mixed phases of InSe and In₂Se₃. The films grown at all voltages in this work were p type in electrical conduction, with bandgaps in the range of (1.70–1.80) eV in both as-deposited and heat-treated forms. The wetting property of In_xSe_y on glass/FTO surfaces indicates that In_xSe_y layers can be helpful as buffer layers or window layers in thin film solar cell development due to their ability to uniformly cover the substrate. The cross-section morphology show smoothening effect of these layers. The experimental results to date are presented in this paper.