Transparent, high mobility InGaZnO thin films deposited by PLD

Transparent oxide semiconductor, InGaZnO, thin films were prepared by pulsed laser deposition at room temperature. The carrier concentration was found to vary by several orders of magnitude from insulating to 10¹⁹ carriers/cm³ depending on the oxygen partial pressure during deposition. Hall mobilities as high as 16 cm²/V s were observed. This is approximately an order of magnitude higher than the mobility of amorphous silicon and indicates that InGaO₃(ZnO)_x with x ≤ 5 may be suitable for transparent, thin film transistor applications. Post-deposition annealing was found to strongly influence the carrier concentration while annealing effects on the electron mobility was less influential.     

The properties of transparent conductive In-Ga-Zn oxide films produced by pulsed laser deposition

To obtain TCO films for wavelengths shorter than the visible range, Ga₂O₃ was added to the In₂O₃-ZnO system as an impurity. Using pulsed laser deposition (PLD), two kinds of targets, InGaZnO₄ and InGaZn₃O_6, were deposited. Although the In-Ga-Zn-O films obtained deviated from the stoichiometry of InGaZnO₄, they were amorphous at a substrate temperature below 250 °C. We obtained the lowest resistivity of 2.77 × 10⁻³ Ω cm within the present experiment at a carrier concentration of 1.38 × 10²⁰ cm⁻³ and a Hall mobility of 16.6 cm²/Vs. The optical band gap energy shifted to higher energies and the transmittance at the blue range was improved dramatically as compared with similar amorphous IZO films.     

Tm-doped ZnO nanorods as a TCO for PV applications

In photovoltaic(PV) devices, a transparent conducting oxide(TCO) film is used as a transparent electrode which permits sun rays to reach to the photoactive semiconducting layers and also to collect the photogenerated electrons. Due to their electrical and optical properties zinc oxide(ZnO) based thin films and nanostructures are considered as an abundant and safer option for TCOs. In this study, undoped and thulium(Tm)-doped ZnO nanorods(NRs) were produced on glass substrates via spin coating and hydrothermal methods. The ZnO samples were described by X-ray diffractometry(XRD). Morphological features of the ZnO samples were investigated with scanning electron microscopy(SEM). It is observed that the all ZnO samples have nanorod shape. The average rods diameter is between 75 and 100 nm. Also,the rods length is found to be between 0.96 and 1.62 μm. Electrical properties of the ZnO samples were performed via four probe method. The conductivity increases with measurement temperature and Tm doping. Optical spectra of the ZnO samples were measured in UV-Vis range and the band gap(E_g) is found to be 3.35 eV.     

Study of a sandwich structure of transparent conducting oxide films prepared by electron beam evaporation at room temperature

ABSTRACT: Transparent conducting ZnO/Ag/ZnO multilayer electrodes having electrical resistance much lower than that of widely used transparent electrodes were prepared by ion-beam-assisted deposition (IAD) under oxygen atmosphere. The optical parameters were optimized by admittance loci analysis to show that the transparent conducting oxide (TCO) film can achieve an average transmittance of 93%. The optimum thickness for high optical transmittance and good electrical conductivity was found to be 11 nm for Ag thin films and 40 nm for ZnO films, based on the admittance diagram. By designing the optical thickness of each ZnO layer and controlling process parameters such as IAD power when fabricating dielectric-metal-dielectric films at room temperature, we can obtain an average transmittance of 90% in the visible region and a bulk resistivity of 5 x 10^-5 ohm-cm. These values suggest that the transparent ZnO/Ag/ZnO electrodes are suitable for use in dye-sensitized solar cells.     

Atmospheric pressure chemical vapour deposition of F doped SnO2 for optimum performance solar cells

The potential of thin film photovoltaic technologies in supporting sustainable energy policies has led to increasing interest in high performance transparent conducting oxides (TCOs), and in particular doped SnO₂, as electrical contacts for solar cells. We have developed an advanced atmospheric pressure chemical vapour deposition process, by applying fast experimentation and using a combinatorial chemistry approach to aid the studies. The deposited films were characterised for crystallinity, morphology (roughness) and resistance to aid optimisation of material suitable for solar cells. Optical measurements on these samples showed low absorption losses, less than 1% around 500 nm for 1 pass, which is much lower than those of industrially available TCOs. Selected samples were then used for manufacturing single amorphous silicon (a-Si:H) solar cells, which showed high solar energy conversion efficiencies up to 8.2% and high short circuit currents of 16 mA/cm². Compared with (commercially available) TCO glasses coated by chemical vapour deposition, our TCO coatings show excellent performance resulting in a high quantum efficiency yield for a-Si:H solar cells.     

Structural, electrical and optical properties of Ga-doped ZnO films on cyclo-olefin polymer substrates

Ga-doped ZnO (GZO) films with a thickness of 100 nm were prepared on cyclo-olefin polymer (COP) and glass substrates at various temperatures below 100 °C by ion plating with direct-current arc discharge. The dependences of the characteristics of GZO films on the substrate temperature Ts were investigated. All the polycrystalline GZO films, which exhibited a high average visible transmittance of greater than 86%, were crystallized with a wurtzite structure oriented along the c-axis. The lowest resistivities of the GZO films were 5.3 × 10^− 4 Ωcm on the glass substrate and 5.9 × 10^− 4 Ωcm on the COP substrate.     

Impact of sheet resistance on 2-D modeling of thin-film solar cells

A rigorous mathematical approach was used to find a relation between the transparent-conductive-oxide (TCO) sheet resistance ρ_S (Ω/□) of a thin-film solar cell and the parameter R (Ω) that describes the TCO resistance in a two-dimensional circuit model. Additionally, the mathematical relationship that connects experimentally derived series resistance R_S (Ω cm²) of the solar cell to the TCO sheet resistance ρ_S (Ω/□) and the bulk semiconductor resistivity ρ (Ω cm) was derived. It was found that the fill factor of the solar cell is governed by a reduced dimensionless TCO sheet resistance that depends only weakly on the type and quality of the solar cell. Parameters corresponding to thin-film Cu(In,Ga)Se₂, two-junction a-Si, and an ideal solar cell were used as concrete examples.     

Development of ZnO-based transparent conductive coatings

We have developed a range of single and multilayer transparent conducting coatings consisting of three to five alternating layers of Al-doped ZnO (AZO) and metals using E-beam evaporation method. The prepared optimized coatings show excellent optical and electrical properties, improved thermal and long-term stability. Optimum thickness of metal and AZO layers was determined for high optical transmittance and good electrical conductivity. X-ray diffraction, spectrophotometer, atomic-force microscopy, scanning electron microscopy and four-point probe were used to explore the possible changes in electrical and optical properties. It was found that the multilayer coatings consisting of Al-doped ZnO and Ag metal show satisfactory properties of low resistance of 5 Ω/sq, high transmittance of 90% and thermal stability up to 500 °C.     

Percolation Mechanism and Characterization of (CdO)y(ZnO)1–y Thin Films

(CdO)_y(ZnO)_1–y thin films have been prepared by the sol–gel process, based on precursor solutions used separately for such oxides. The Cd/(Cd + Zn) atomic ratio in solution ranged from 0 to 0.32. These compositions were selected on the basis of an observed abrupt fall, of ca. four orders of magnitude, in the resistivity of the films within this range. Such a resistivity drop, with a threshold value of around y = 0.17, is consistent with a percolation mechanism in a three‐dimensional, random, two‐phase system composed of isotropic, sphere‐like, conducting CdO regions embedded in a highly resistive ZnO matrix. Optical measurements show that the films are highly transparent, above 90 % transmission, for wavelengths ≥600 nm. The optical absorption edge shifts to longer wavelengths as the Cd content in the film increases. On the basis of the percolation mechanism observed in the multicomponent system (CdO)_y(ZnO)_1–y, possible future pathways are proposed for the design and construction of highly efficient, transparent, conducting oxides.     

基于TCO模式的采购成本分析法的应用研究

通过供应链管理降低采购成本是制造企业降低生产成本的有效途径.以一家家用电器制造企业为背景,介绍了战略性采购成本分析方法--总拥有成本分析模式(TCO)在降低采购成本的应用方法.应用结果说明降低采购成本不应仅仅考虑采购价格,应从系统的角度分析问题,运用因果关系将供应商成本分配到产品上,然后找出关键因素降低成本.