Query: Transparent conducting oxide semiconductors for transparent electrodes

Candidate papers:

abstract: The present status and prospects for further development of polycrystalline or amorphous transparent conducting oxide (TCO) semiconductors used for practical thin film transparent electrode applications are presented in this paper. The important TCO semiconductors are impurity doped ZnO, In2O3 and SnO2 as well as multicomponent oxides consisting of combinations of ZnO, In2O3 and SnO2, including some ternary compounds existing in their systems. Development of these and other TCO semiconductors is important because the expanding need for transparent electrodes for optoelectronic device applications is jeopardizing the availability of indium tin oxide (ITO) whose main constituent, indium, is a very expensive and scarce material. Al and Ga doped ZnO (AZO and GZO) semiconductors are promising as alternatives to ITO for thin film transparent electrode applications. In particular, AZO thin films, with a low resistivity of the order of 10 5 O cm and source materials that are inexpensive and non toxic, are the best candidates. However, further development of the deposition techniques, such as magnetron sputtering or vacuum arc plasma evaporation, as well as of the targets is required to enable the preparation of AZO and GZO films on large area substrates with a high deposition rate.
author_names: Tadatsugu Minami
title: Transparent conducting oxide semiconductors for transparent electrodes
year: 2005

abstract: The various applications of transparent conducting oxides (TCO) e.g. as electrodes in flat panel displays and solar cells or as low emissivity coatings have stimulated extensive research on their fabrication and properties. Recent experimental and theoretical studies of defect properties have considerably improved the understanding of the limitations of the electrical conductivity of both n and p type transparent conductors and of the structural and electronic surface properties of the most important TCO materials. Development of emerging and future applications in the area of transparent thin film electronics with oxide semiconductors as well as the improvement of existing applications require a detailed control of the Fermi level position in the bulk and at surfaces and interfaces of polycrystalline and amorphous TCO materials. This feature article describes how the important parameters for such control can be identified using photoelectron spectroscopy with in situ sample preparation. The parameters influencing doping, work functions, ionization potentials, and surface band bending as well as energy band alignment at interfaces are described and discussed providing a fundamental understanding of important material properties for tailoring TCOs in electronic devices.
author_names: Andreas Klein
title: Transparent Conducting Oxides: Electronic Structure Property Relationship from Photoelectron Spectroscopy with in situ Sample Preparation
year: 2012

abstract: This dissertation focuses on characterizing the nanoscale and surface averaged electrical properties of transparent conducting oxide (TCO) electrodes such as indium tin oxide (ITO) and transparent metal oxide (MO) electron selective interlayers (ESLs) such as zinc oxide (ZnO) the ability of these materials to rapidly extract photogenerated charges from organic semiconductors (OSCs) used in organic photovoltaic (OPV) cells, and evaluating their impact on the power conversion efficiency (PCE) of OPV devices. In Chapter 1, we will introduce the fundamental principles regarding the need for low cost power generation, the benefits of OPV technologies, as well as the key principles that govern the operation of OPV devices and the key innovations that have advanced this technology. In Chapter 2 of this dissertation, we demonstrate an innovative application of conductive probe atomic force microscopy (CAFM) to map the nanoscale electrical heterogeneity at the interface between an electrode, such as ITO, and an OSC such as the p type OSC copper phthalocyanine (CuPc)(MacDonald et al. (2012) ACS Nano, 6, p. 9623) In this work we collected arrays of J V curves, using a CAFM probe as the top contact of CuPc/ITO systems, to map the local J V responses. By comparing J V responses to known models for charge transport, we were able to determine if the local rate limiting step for charge transport is through the OSC (ohmic) or the CuPc/ITO interface (nonohmic) These results strongly correlate with device PCE, as demonstrated through the controlled addition of insulating alkylphosphonic acid self assembled monolayers (SAMs) at the ITO/CuPc interface. Subsequent chapters focus on the electrical property characterization of RF magnetron sputtered ZnO (sp ZnO) ESL films on ITO substrates. We have shown that the energetic alignment of ESLs and the organic semiconducting (OSC) active materials plays a critical role in determining the PCE of OPV devices and the appearance of, or lack thereof, UV light soaking sensitivity. For ZnO and fullerene interfaces, we have shown that either minimizing the oxygen partial pressure during ZnO deposition or exposure of ZnO to UV light minimizes the energetic offset at this interface and maximizes device PCE. We have used a combination of device testing, device modeling, and impedance spectroscopy to fully characterize the effects that energetic alignment has on the charge carrier transport and charge carrier distribution within the OPV device. This work can be found in Chapter 3 of this dissertation and is in preparation for publication. We have also shown that the local properties of sp ZnO films varies as a function of the underlying ITO crystal face. We show that the local ITO crystal face determines the local nucleation and growth of the sp ZnO films. We demonstrate that this effects the morphology, the chemical resistance to etching as well as the surface electrical properties of the sp ZnO films. This is likely due to differences in the surface mobility of sputtered Zn and O atoms on these.
author_names: Gordon A MacDonald
title: Nanoscale Characterization of the Electrical Properties of Oxide Electrodes at the Organic Semiconductor Oxide Electrode Interface in Organic Solar Cells
year: 2015

abstract: Transparent conducting oxides (TCOs) and transparent oxide semiconductors (TOSs) have become necessary materials for a variety of applications in the information and energy technologies, ranging from transparent electrodes to active electronics components. Perovskite barium stannate (BaSnO3) a new TCO or TOS system, is a potential platform for realizing optoelectronic devices and observing novel electronic quantum states due to its high electron mobility, excellent thermal stability, high transparency, structural versatility, and flexible doping controllability. This article reviews recent progress in the doped BaSnO3 system, discussing the wide range of physical properties, electron scattering mechanism, and demonstration of key semiconducting devices such as pn diodes and field effect transistors. Moreover, we discuss the pathways to achieving two dimensional electron gases at the interface between BaSnO3 and other perovskite oxides and describe remaining challenges for observing novel quantum phenomen.
author_names: Woong-Jhae Lee

Hyung Kim

Jeonghun Kang

D H Jang

Tai-hoon Kim

Jeong Hyuk Lee

Kee Hoon Kim
title: Transparent Perovskite Barium Stannate with High Electron Mobility and Thermal Stability
year: 2017

abstract: Recently, a new field in photovoltaics (PV) has emerged, focusing on solar cells that are entirely based on metal oxide semiconductors. The all oxide PV approach is very attractive due to the chemical stability, nontoxicity, and abundance of many metal oxides that potentially allow manufacturing under ambient conditions. Already today, metal oxides (MOs) are widely used as components in PV cells such as transparent conducting front electrodes or electron transport layers, while only very few MOs have been used as light absorbers. In this Perspective, we review recent developments of all oxide PV systems, which until today were mostly based on Cu2O as an absorber. Furthermore, ferroelectric BiFeO3 based PV systems are discussed, which have recently attracted considerable attention. The performance of all oxide PV cells is discussed in terms of general PV principles, and directions for progress are proposed, pointing toward the development of novel metal oxide semiconductors using combinatorial methods.
author_names: Sven Ruhle

Assaf Y Anderson

Hannah-Noa Barad

Benjamin Kupfer

Yaniv Bouhadana

Eli Rosh-Hodesh

Arie Zaban
title: All Oxide Photovoltaics.
venue: The journal of physical chemistry letters
year: 2012

abstract: The need for a high performance, earth abundant transparent conducting oxides (TCOs) is ever present in the expanding electronics and photovoltaics industry. TCOs possess large optical band gaps 3.1 eV) in order to avoid the absorption of visible light, resistivities as low as ~10 5 Ocm as well as large carrier concentrations 1020 cm 3) All the industrially used TCOs (i.e. ITO, ZnO:Al, SnO2:F) are n type, which limits their applications to those of transparent electrodes. To extend the utility and applications of TCOs further, p n junctions composed of all oxide TCOs must be achieved, meaning that the discovery of a high performance, p type TCO has become a much sought after goal for materials scientists. Decades of attempts to fabricate the elusive p type TCO have been centred on doping of the natively n type TCOs to make them p type, with little success. Arguably the flagship TCO material is In2O3:Sn (Tin doped Indium Oxide, ITO) with resistivities as low as 10 5 Ocm making this material ideal for consumer electronics. A main limitation of this material however, is the high cost of indium and the rarity of the element in the earth's crust which drives the search for a cheaper alternative. Stannia (SnO2 or stannic oxide) is an n type, wide band gap oxide semiconductor which crystallizes in the tetragonal rutile (Cassiterite) structure. It possesses a fundamental band gap of 3.6 eV at the Gamma point, can achieve conductivities of ~104 Scm 1 when donor doped, and displays a high thermal and chemical stability, making it excellent for transparent conducting oxide (TCO) and gas sensing applications. High conductivities can be achieved by doping with Antimony (Sb) or Fluorine (F) which are the most common choice for donor dopant in SnO2 resulting in resistivities as low as 10 4 Ocm, which falls short of the performance of ITO. One reason is that these these dopants appear to be inherently self limiting. In this presentation I will present a survey of the defect chemistry of SnO2, explaining why the material can never be made p type, and identifying novel doping strategies which can surpass the self limitations of the currently utilsed donor dopants.
author_names: Jana Tittmann-Otto

Martin T Hartmann

J Ullrich

Stefan Schulz
title: Workshop on Charge Trapping Defects in Semiconductors and Insulators
year: 2017

abstract: Abstract Dense tin oxide based ceramic semiconductors have a high potential as electrodes for aluminum production, glass industry, sputtering targets for transparent conducting thin films, varistors, and thermoelectrics due to their specific electrical properties, high corrosion resistance and ability to withstand high temperatures. The application of these ceramics is still limited because of the necessity to reach density of 99% of TD or greater and high electrical conductivity, and because of the manufacturing difficulties to produce components of different shapes and sizes with low cost. The paper reviews the results of the works conducted towards obtaining tin oxide based ceramics with density up to 99.5+ of TD through low temperature pressureless sintering. The selected sintering aids/dopants and firing conditions promoted both liquid phase sintering and electrical conductivity. The uniform microcrystalline structure is obtained.
author_names: Eugene Medvedovski
title: Tin oxide based ceramics of high density obtained by pressureless sintering
year: 2017

abstract: Sodium beta alumina (SBA) has high two dimensional conductivity, owing to mobile sodium ions in lattice planes, between which are insulating AlO(x) layers. SBA can provide high capacitance perpendicular to the planes, while causing negligible leakage current owing to the lack of electron carriers and limited mobility of sodium ions through the aluminium oxide layers. Here, we describe sol gel beta alumina films as transistor gate dielectrics with solution deposited zinc oxide based semiconductors and indium tin oxide (ITO) gate electrodes. The transistors operate in air with a few volts input. The highest electron mobility, 28.0 cm2 V( 1) s( 1) was from zinc tin oxide (ZTO) with an on/off ratio of 2 x 10(4) ZTO over a lower temperature, amorphous dielectric, had a mobility of 10 cm2 V( 1) s( 1) We also used silicon wafer and flexible polyimide aluminium foil substrates for solution processed n type oxide and organic transistors. Using poly(3,4 ethylenedioxythiophene) poly(styrenesulphonate) conducting polymer electrodes, we prepared an all solution processed, low voltage transparent oxide transistor on an ITO glass substrate.
author_names: Bhola Nath Pal

Bal M Dhar

Kevin C See

Howard E Katz
title: Solution deposited sodium beta alumina gate dielectrics for low voltage and transparent field effect transistors.
venue: Nature materials
year: 2009

abstract: Tin oxide, an n type wide direct band gap semiconductoris promisingly used material for detection of wide variety of gases such as LPG, CO, and volatile organic compound (VOC'S) and many different applications such as high performance capacitive behaviour, transparent conducting electrodes, transistors, light emitting diodes (LEDs) and solar cells. The electrical conductivity of the nanoparticles are dependent on the density of preadsorbed oxygen ions on its surface. The detection mechanism of gas is based on the reversible change of conductivity of the surface of metal oxide semiconductors particles/grains induced by gas solid interaction. Several strategies have been adopted to enhance the performance of gas sensors; including doping with aliovalent ions (e.g. Cu, Zn, In) catalytically active additives.
author_names: Mahendra Kumar
title: Gas Sensing Properties of Zn Doped TIN Oxide Nanoparticles with Methanol
year: 2016

abstract: One dimensional nanowire arrays directly grown on substrates have been recognized to be superior to two dimensional thin films and nanoparticle films since they demonstrate in general single crystallinity, larger surface area, fast charge separation, and good contact with substrates. Accordingly, they provide an accessible way to the development of high performance devices such as photovoltaic cells, sensors, photocatalysts, electrodes, light emitters, etc. Although high temperature vapor phase synthesis is the most commonly employed method to produce high crystallinity and high density one dimensional nanostructures with high purity, it is not acceptable in terms of the growing demand for the use of TCO (transparent conducting oxide) glass substrates, cost effectiveness, and large scale mass production. Also, it is very difficult to control the precursor vapor pressures to meet the stoichiometry of many compound semiconductors through the vapor phase growth. In this context, there is a high need for the development of appropriate and efficient wet chemical growth methods for one dimensional nanostructures for a broad range of applications. In this review, we provide an overview of various low temperature wet chemical synthetic approaches. In each fabrication method, we summarize the brief synthetic routes, microstructures, and the mechanism of anisotropic growth. In addition, the last section introduces various applications of one dimensional nanostructure arrays. This review provides the current status and prospects of the growth of one dimensional nanostructure arrays via wet chemical routes.
author_names: Joo Won Lee

Young Min Kim

Yun-Mo Sung
title: Wet chemical growth of semiconductor 1 D nanostructure arrays on conductive substrates
year: 2019