Fluorine Tin Oxide Substrate Research Articles

Effect of an electrodeposited TiO2 blocking layer on efficiency improvement of dye-sensitized solar cell

A TiO2 blocking layer in DSSC provides good adhesion between the fluorinated tin oxide (FTO) and an active TiO2 layer, and represses the electron back transport between electrolyte and FTO by blocking direct contact. In addition, it offers a more uniform layer than bare FTO glass. In this study, a dense TiO2 layer is prepared by electrodeposition technique onto an FTO substrate, and it is further used for efficiency measurement of dye-sensitized solar cell (DSSC). The thickness of TiO2 blocking layers is controlled by applied voltage and deposition time. The morphology and crystalline structure of TiO2 blocking layers are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The effect of thickness of TiO2 blocking layers on transmittance is also examined by UV-vis spectrophotometer. For the best performance of the cell efficiency, the optimum blocking layer thickness is about 450 nm fabricated at 0.7 V for 20 min. The conversion efficiency from the DSSC including the optimum blocking layer is 59.34% improved compared to the reference cell from 2.41% to 3.84%. It demonstrates that the electrodeposition is a useful method to produce TiO2 blocking layer for DSSC applications.

Efficiency improvement in organic solar cells by inserting a discotic liquid crystal

In this paper, we reported a simple method to increase the power conversion efficiencies (PCEs) of solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester derivatives blended active layer. The approach includes insertion of a discotic liquid crystal [2,3,6,7,10,11]-Hexabutoxytriphenylene (HAT4) at the interface between the active layer and a hole transporting layer. HAT4 molecules distribute in the active layer to form a more efficient pass way for carriers leading to improve the charge mobility. The experiments also included different hole transporting layers (HTLs) (PEDOT:PSS, MoO 3 and NiO) deposited on fluorine-tin oxide substrates, respectively. The results showed that both short-circuit current ( J SC) and fill factor (FF) were increased without open-circuit voltage sacrifice. Maximum 43% increase in PCE with the insertion of HAT4 for three kinds of HTLs was obtained in the devices compared with that of the reference ones. The mechanisms behind J SC and FF increase are discussed.

Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation.

A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm-2) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm-2). When SHI irradiation of oxygen ions of fluence 1 × 1013 ions/cm2 was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs.

Flame synthesis of tungsten oxide nanostructures on diverse substrates

One-dimensional (1D) tungsten oxide nanostructures show great potential for applications in the areas of batteries, photoelectrochemical water-splitting, electrochromic devices, catalysts and gas sensors. 1D tungsten oxide nanostructures are currently synthesized by physical or chemical vapor deposition, which are limited by low temperatures, the need for vacuum conditions, frequently expensive catalysts, and difficulty in scaling up for mass-production. These limitations, however, can be overcome by flame synthesis. Here, using a co-flow multi-element diffusion burner, we demonstrate the atmospheric, catalyst-free, rapid, mild and scalable flame synthesis of diverse, quasi-aligned, large density, and crystalline tungsten oxide nanostructures on a variety of substrates. Specifically, under fuel-rich conditions, monoclinic 1D W 18O 49 nanowires and nanotubes were grown on tungsten, iron, steel and fluorinated tin oxide (FTO) substrates, with controlled diameters ranging from 10 to 400 nm and axial growth rates ranging from 2 to 60 μm/h. Monoclinic 1D WO 3 nanowires and nanotubes were grown, instead, on silicon and silicon dioxide substrates. Under fuel-lean conditions, diverse WO 3 nanostructures, including monoclinic 1D nanowires, cubic 2D nanobelts and monoclinic 3D nanocones were grown on tungsten and FTO substrates. The success of this versatile flame synthesis method is attributed to the large tunability of several synthesis parameters, including the flame stoichiometry, the tungsten source and growth substrate temperatures, the tungsten oxide vapor concentration, and the material of the growth substrate. This flame synthesis method can be extended to synthesize other 1D transition metal oxides as well, enabling many large-scale electronic and energy conversion applications.

Hybrid p-type ZnO film and n-type ZnO nanorod p– n homo-junction for efficient photovoltaic applications

Simple hybrid p– n homo-junctions using p-type ZnO thin films and n-type nanorods grown on fluorine tin oxide (FTO) substrates for photovoltaic applications are described. The ZnO nanorods (1.5 μm) were synthesized via an aqueous solution method with zinc nitrate hexahydrate and hexamethylenetetramine on ZnO seed layers. The 10-nm-thick ZnO seed layers showed n-type conductivity on FTO substrates and were deposited with a sputtering-based method. After synthesizing ZnO nanorods, aluminum-nitride co-doped p-type ZnO films (200 nm) were efficiently grown using pre-activated nitrogen (N) plasma sources with an inductively-coupled dual-target co-sputtering system. The structural and electrical properties of hybrid p– n homo-junctions were investigated by scanning electron microscopy, transmittance spectrophotometry, and I– V measurements.

Control of ZnO nanorod array alignment synthesized via seeded solution growth

The critical factors that determine the degree of alignment of dense ZnO nanorod (NRAs) arrays synthesized via a two-step seeding and solution growth process were systematically examined, with a goal of optimizing the array density and surface area for hybrid organic–inorganic photovoltaic (PV) devices. Unexpectedly, we found that the degree of alignment of ZnO nanorod arrays depended strongly on the ambient humidity level during the seeding step. Close-packed ZnO nanorod arrays with [0 0 1] axis perpendicular to the substrate were obtained only when seeded at >20% relative humidity (RH) at room temperature (RT), according to data from scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. In addition, when the seeding RH was raised to >60%, the polydispersity in the diameter and length of the ZnO nanorods increased, although good alignment was maintained. As a result, we determined an optimal seeding humidity of 30–40% for the synthesis of ordered ZnO nanorod arrays. Atomic force microscopy and contact angle measurements revealed that the density of ZnO seeds was significantly lower below the 20% relative humidity threshold, indicating that water vapor plays a critical role in generating insoluble zinc hydrolysis products that act as nucleation sites for the subsequent growth of ZnO nanorods. Finally, we found that the alignment of the ZnO nanorod arrays was strongly disrupted as the roughness of the underlying fluorinated tin oxide substrate increased. The improved control of the morphology of ZnO nanorod arrays may lead to improved carrier collection of conducting polymer-ZnO nanorod array hybrid PV devices.