Conducting Oxide Coated Glass Substrates Research Articles

Enhancing the performance of poly(3-hexylthiophene)/ZnO nanorod arrays based hybrid solar cells through incorporation of a third component

Sparse ZnO nanorod arrays (NRAs) are fabricated on transparent conducting oxide coated glass substrates by using a modified liquid phase epitaxial growth method. By adjusting the polymer concentrations and the spin-coating parameters, full infiltration of poly(3-hexylthiophene) (P3HT) into the as-prepared ZnO NRAs is achieved at 130°C in vacuum. A third component is incorporated into the P3HT/ZnO NRAs ordered bulk heterojunctions (BHJs) either through ZnO surface modification with N719 dye or CdS shell layer or by inclusion of a fullerene derivative into the P3HT matrix. Experimental results indicate that performances of the hybrid solar cells are improved greatly with the incorporation of a third component. However, the working principles of these third components differ from one another, according to morphology, structure, optical property, charge transfer and interfacial properties of the composite structures. An ideal device architecture for hybrid solar cells based on P3HT/ZnO NRAs ordered BHJs is proposed, which can be used as a guidance to further increase the power conversion efficiency of such solar cells.

Fabrication of CdS/Hg(1−x)CdxTe nanowire heterostructures on conductive glass using templated electrodeposition

Single-material and heterojunction nanowires were fabricated from CdS and Hg(1−x)CdxTe (MCT) in anodic aluminum oxide templates grown on transparent conductive oxide coated glass substrates. Structural and compositional analyses were carried out by electron microscopy, elemental analysis and x-ray diffraction. CdS was deposited using potentiostatic electrodeposition, forming CdS nanowires with a 1:1 stoichiometry and wurtzite structure. MCT was also deposited using potentiostatic electrodeposition, forming MCT nanowires with a stoichiometry of Hg0.24Cd0.76Te and a zinc blende structure. Annealing of the electrodeposited MCT nanowires increased crystallite size from ~9nm to ~23nm in the (111) direction. Heterojunction nanowires were prepared by sequential electrodeposition of CdS and MCT with control over the length and diameter. These materials have a desirable band gap and geometry for multiple-exciton generation studies for nanostructured photovoltaics applications.

Preparation of porous glass films using phase separation phenomenon and growth behavior of phase-separated structure

We report the preparation of porous glass films on transparent conductive oxide-coated glass substrates using the phase separation phenomena and the growth behavior of the phase-separated structure. We confirmed that the etched glass films are composed of microscale pores, a three-dimensional porous framework of SiO2-rich phase with widths of about 40–300 nm, and a thin surface layer of about 40–90 nm thick. The SiO2-rich phase grew by diffusion-dominated growth and then viscous flow-dominated growth.

Electric field assisted aerosol assisted chemical vapor deposition of nanostructured metal oxide thin films

Thin films of vanadium dioxide were deposited using a novel electric field assisted chemical vapor deposition methodology onto glass and gas sensor substrates. Electric fields were generated during the deposition reaction by applying a potential difference across the inter-digitated electrodes of the gas sensor substrate or buy applying an electric field between two transparent conducting oxide coated glass substrates. The deposited films were analyzed and characterized using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, atomic force microscopy and contact angle measurements. It was found that applying an electric field led to large changes in film microstructure, preferential orientation and changes in the film growth rate. This led to significant changes in materials properties such as increased surface roughness and enhanced wetting behaviour. Electric field-assisted chemical vapour deposition shows great promise as a method for nano-structuring and tailoring the properties of metal oxide thin films.

Surface chemistry and growth mechanism of highly oriented, single crystalline TiO2nanorods on transparent conducting oxide coated glass substrates

The fabrication of one-dimensional (1D) rods or wires of titania in desired crystalline facets is quite exciting due to unique optoelectronic properties. The single crystalline, oriented nanorods directly grown on transparent conducting oxide (TCO) substrates are finding a lot of interest in solar photovoltaics and several other optoelectronic devices due to enhanced electron transport and lower exciton recombination rates. However, the growth of desired crystalline facets of highly oriented, single crystalline nanorods on different substrates and understanding the interplay between the surface chemistry and growth mechanism still remain a non-trivial and challenging task. Here, for the first time, the kinetically controlled growth of the (310) facet of TiO2 nanorods on fluorine-doped tin oxide (FTO) coated glass substrate has been reported which is in contrast to the previously reported (002) faceted TiO2 nanorods. In addition to this, the growth of (110) facet TiO2 nanorods using amorphous fluorine doped silicon oxide (FSO) as a substrate is also demonstrated. In this paper, it is shown that two different faceted TiO2 nanorods can be synthesized following same synthetic condition by varying only the material properties of the substrate. To investigate the role of substrate chemistry on the morphology and single crystallinity of TiO2 nanorods, electron microscopy, XPS and contact angle measurements have been done. The results clearly indicate an important link between the surface chemistry and morphology of TiO2 nanorods. It can be assumed that there is a role of OH− and water groups which are responsible for the growth of plane (110) which has less surface energy. The observation of (310) facet is quite surprising and can be explained based on FTO crystallinity. It is possible to tune the diameter of the titania nanorods by further coating the FTO substrate with a thin gold layer due to increase in the hydrophilicity of the substrate. Finally, a light to electricity conversion efficiency of 2.5% could be achieved by using vertically grown titania nanorods on FTO as the photoanode in a dye sensitized solar cell (DSSC).

Photoelectrochemical properties of CdS sensitized ZnO nanorod arrays: Effect of nanorod length

The vertically aligned ZnO nanorod arrays were achieved from aqueous chemical route on soda lime and transparent conducting oxide coated glass substrates. The length of nanorods was varied from 1.6 μm to 4.5 μm by varying deposition time. The aspect ratio of ZnO nanorod was increased with increasing deposition time. Cadmium sulfide (CdS) nanoparticles have been subjected to self-assemble onto ZnO nanorods (ZNRs) using chemical bath deposition method. The synthesized CdS/ZnO nanorod arrays were characterized for their optical, structural, and morphological properties with UV-visible absorption spectroscopy (UV-Vis), x-ray diffraction, energy-dispersive x-ray analysis, x-ray photoelectron spectroscopy, contact angle measurement, and scanning electron microscopy. The cross-section images of the samples clearly depict different lengths of ZnO nanorods. UV-vis absorption spectrum shows the significant red shifting after covering of the CdS nanoparticles over the ZnO nanorods. The lengths of ZnO nanorod arrays are an effective parameter to improve the photoelectrochemical performance of CdS nanoparticles sensitized ZnO solar cells. We obtain a highest total light-to-electricity power conversion efficiency of 1.2% for relatively larger area (1 cm2) solar cells.

Optical, electrochemical and morphological investigations of poly (3,4-propylenedioxythiophene)–sultone (PProDOT–S) thin films

In this paper, we have carried out thin film characterization of poly(3,4-propylenedioxythiophene)–sultone (PProDOT–S), a derivative of electrochromic poly(3,4-propylenedioxythiophene) (PProDOT). PProDOT–S was deposited onto transparent conducting oxide coated glass substrates by solution casting method. Single wavelength spectrophotometry is used to monitor the switching speed and contrast ratio at maximum wavelength (λ max). The percentage transmittance at the λ max of the neutral polymer is monitored as a function of time when the polymer film is repeatedly switched. This experiment gives a quantitative measure of the speed with which a film is able to switch between the two states i.e. the coloured and the bleached states. PProDOT–S films were switched at a voltage of 1·9 V with a switching speed of 2 s at λ max of 565 nm and showed a contrast of ∼37%. Cyclic voltammetry performed at different scan rates have shown the characteristic anodic and cathodic peaks. The structural investigations of PProDOT–S films by IR spectra were in good agreement with previously reported results. Raman spectra of PProDOT–S showed a strong Raman peak at 1509 cm − 1 and a weak peak at 1410 cm − 1 due to the C = C asymmetric and symmetric stretching vibrations of thiophene rings. The morphological investigations carried out by using scanning electron microscope (SEM) of polymer films have shown that these polymers are found to be arranged in dense packed clusters with non-uniform distribution having an average width and length of 95 nm and 160 nm, respectively.

An analysis of temperature dependent current–voltage characteristics of Cu 2O–ZnO heterojunction solar cells

Carrier transport and recombination mechanisms in Cu 2O–ZnO heterojunction thin film solar cells were investigated through an analysis of their current–voltage characteristics in the dark and under various illumination intensities, as a function of temperature between 100 K and 295 K. The Cu 2O–ZnO heterojunction solar cells were prepared by metal organic chemical vapor deposition of Cu 2O on ZnO films sputtered on transparent conducting oxide coated glass substrates. Activation energies extracted from the temperature dependence of the J–V characteristics reveals that interface recombination is the dominant carrier transport mechanism. Tunneling across an interfacial barrier also plays an important role in current flow and a thin TiO 2 buffer layer reduces tunneling. A high open circuit voltage at low temperature (~ 0.9 V at around 100 K) indicates that Cu 2O–ZnO heterojunction solar cells have high potential as solar cells if the recombination and tunneling at the interface can be suppressed at room temperature.

Cathodic deposition of CdSe films from dimethyl formamide solution at optimized temperature

In the present paper, thin film CdSe compound semiconductors have been electroplated on transparent conducting oxide coated glass substrates from nonaqueous dimethyl formamide bath containing CdCl2, KI and Se under controlled temperature ranging from 100 to 140°C. Thickness of the deposited films as obtained through focussed ion beam technique as well as their microstructural and photoelectrochemical properties have been found to depend on temperature. The film growth was therefore optimized at a bath temperature ∼125°C. The formation of crystallites in the range of 100–150nm size has been ascertained through atomic force microscopy and scanning electron microscopy. Energy dispersive analysis of X-rays for the as deposited film confirmed the 1:1 composition of CdSe compound in the matrix exhibiting band-gap energy of 1.74eV. Microstructural properties of the deposited films have been determined through X-ray diffraction studies, high-resolution transmission electron microscopy and electron diffraction pattern analysis. Electrochemical impedance spectroscopy and current-potential measurements have been performed to characterize the electrochemical behavior of the semiconductor–electrolyte interface. The photo-activity of the films have been recorded in polysulphide solution under illumination and solar conversion efficiency ≥1% was achieved.

Study of Electrochromic Devices Incorporating a Polymer Gel Electrolyte Component

Electrochromic materials have attracted considerable attention during the last two decades as a consequence of their potential application in several different types of optical devices. Examples of these devices include intelligent windows and time labels. In this paper the authors describe results obtained with thin tungsten oxide films produced at room temperature by rf magnetron sputtering under an argon and oxygen atmosphere on transparent conductive oxide coated glass substrates. To protect the surface of the electrochromic film, prevent water absorption and obtain a good memory effect under open circuit voltages, a layer of Ta2O5 was deposited over the WO3 films. In this study, the effect of different electrolyte compositions on the open circuit memory of optical devices has been characterized. The best results were obtained for electrochromic devices with polymer gel p(TMC)3LiClO4 and p(TMC)8LiClO4 electrolytes. These prototype devices present an overall transmittance of ~75% in their bleached state and after coloration 40.5 and 52.5% respectively. These devices also show memory effect and an optical density considered satisfactory for some electrochromic applications.

Sol-gel processed nanostructured CeO2–TiO2 thin films for electrochromic applications

Mixed oxide films based on Ce and Ti have been deposited on transparent conducting oxide coated glass substrates using the sol-gel technique. The nanostructural characteristics of the films derived from different precursor materials (cerium chloride and ceric ammonium nitrate) have been evidenced from the transmission electron microscopic analysis. Cyclic voltammetric investigations have shown that the Li ion diffusion in the films has been influenced by the size of the CeO2 nanograins and their distribution in the amorphous TiO2 matrix. Multiple step chronoamperometric studies have revealed that the higher thickness of the films obtained using cerium chloride has resulted in the same a greater capacity to intercalate the Li ions in view of the higher number of active insertion sites for the Li ion. The latter has consequently led to improved reversibility of the electrochromic device comprising the counter electrode based on cerium chloride. The slower coloration–bleaching kinetics of the primary working electrode (WO3) in the configuration comprising the ceric ammonium nitrate based counter electrode exemplifies the advantage of using cerium chloride for depositing CeO2–TiO2 thin films for electrochromic applications.

Studies on electrosynthesized semiconducting zinc selenide thin films

The electrosynthesis of ZnSe thin films from aqueous acidic bath onto transparent conducting oxide coated glass substrates is described. The deposition potential range suitable for the deposition has been optimized using cyclic voltammetry. The influence of various deposition parameters on the structural and optical properties of the films is described. The optical constants ‘n’ and ‘k’ and the complex dielectric constants of the electrosynthesized ZnSe thin films are estimated for various wave length region. The surface morphological studies and the composition analysis are carried out and the results are discussed.

Luminescent Characteristics of Tb Doped Al2 O 3 Films Deposited by Spray Pyrolysis

Aluminum oxide films doped with Tb have been deposited by the spray pyrolysis technique on either plain or conductive oxide coated glass substrates at temperatures in the range of 270–450°C. The photoluminescence emission from these films shows well‐defined peaks at 490 and 550 nm, which are associated with Tb transitions, and a broad peak centered at 430 nm. The relative intensity of these peaks is strongly dependent on the type of substrate, the substrate temperature during deposition, and the amount of Tb incorporated in the film. Electron microscopy and energy dispersion spectroscopy (EDS) measurements indicate that changes induced on morphology and chemical composition, as well as diffusion into the substrate, are correlated with the luminescence efficiency characteristics of these films. The role as a diffusion barrier of a thin film on the substrate is also studied using EDS. Auger electron spectroscopy has been used to estimate the stoichiometry of the films.

Determination of the Efficiency Enhancement Due to Scattering from Rough TCO Contact for a-Si:H P-I-N Solar Cells

AbstractA-Si:H p-i-n solar cells were deposited on textured transparent conducting oxide coated glass substrates to experimentally determine the enhancement in the short circuit current density. It was found that the optical thickness can be increased by a factor from 3 to 5. These results agree reasonably well with the predictions of optical enhancement theory.