Among other intrinsic open-volume defects, copper vacancy (VCu) has been theoretically identified as the major acceptor in p-type Cu-based semiconducting transparent oxides, which has potential as low-cost photovoltaic absorbers in semi-transparent solar cells. A series of positron annihilation experiments with pure Cu, Cu2O, and CuO presented strong presence of VCu and its complexes in the copper oxides. The lifetime data also showed that the density of VCu was becoming higher as the oxidation state of Cu increased which was consistent with the decrease in the formation energy of VCu. Doppler broadening measurements further indicated that electrons with low momentum made more contribution to the contributed as pure Cu oxidizes to copper oxides. The metastable defects are known to be generated in Cu2O upon illumination and it has been known to affect the performance of Cu2O-based hetero-junctions used in solar cells. The metastable effect was studied using positron annihilation lifetime spectroscopy and its data showed the change in the defect population upon light exposure and the minimal effect of lightinduced electron density increase in the bulk of materials to the average lifetime of the positrons. The change in the defect population is concluded to be related to the dissociation and association of VCu - VCu complexes. For example, the shorter lifetime under light was ascribed to the annihilation with smaller size vacancies, which explains the dissociation of the complexes with light illumination. Doppler broadening of the annihilation was independent of light illumination, which suggested that the chemical nature of the defects remained without change upon their dissociation and association - only the size distribution of copper vacancies varied. The delafossite metal oxides, CuMIIIO2 are emerging wide-bandgap p-type semiconductors. In this research, the formation energies of structural vacancies are calculated using Van Vechten cavity model as an attempt to study the effect of the size of the MIII cation in the delafossites starting from Cu2O. Comparison of the formation energies between Cu2O and delafossite oxides clearly showed that the equilibrium concentration of the vacancies depended strongly on the structural parameters varied by the presence of different MIII cations. In particular, the size of the MIII cation greatly influenced the defect formation energies of VCu. It was observed from our calculations, as the size increases the formation energy decreases.

Transparent conducting materials are key elements in a wide variety of current technologies including flat panel displays, photovoltaics, organic, low-e windows and electrochromics. The needs for new and improved materials is pressing, because the existing materials do not have the performance levels to meet the ever- increasing demand, and because some of the current materials used may not be viable in the future. In addition, the field of transparent conductors has gone through dramatic changes in the last 5-7 years with new materials being identified, new applications and new people in the field. “Handbook of Transparent Conductors” presents transparent conductors in a historical perspective, provides current applications as well as insights into the future of the devices. It is a comprehensive reference, and represents the most current resource on the subject.

Metal Oxide Defects: Fundamentals, Design, Development and Applications provides a broad perspective on the development of advanced experimental techniques to study defects and their chemical activity and catalytic reactivity in various metal oxides. This book highlights advances in characterization and analytical techniques to achieve better understanding of a wide range of defects, most importantly, state-of-the-art methodologies for controlling defects. The book provides readers with pathways to apply basic principles and interpret the behavior of metal oxides. After reviewing characterization and analytical techniques, the book focuses on the relationship of defects to the properties and performance of metal oxides. Finally, there is a review of the methods to control defects and the applications of defect engineering for the design of metal oxides for applications in optoelectronics, energy, sensing, and more. This book is a key reference for materials scientists and engineers, chemists, and physicists. Reviews advances in characterization and analytical techniques to understand the behavior of defects in metal oxide materials Introduces defect engineering applied to the design of metal oxide materials with desirable properties Discusses applications of defect engineering to enhance the performance of materials for a wide range of applications, with an emphasis on optoelectronics

Recently Cu-based transparent conducting delafossite compounds have been found to exhibit p-type conductivity either intrinsically or through various doping schemes. The development of a single oxide compound which can be effectively doped both n- and p-type would make a number of interesting transparent devices a reality. In this work, bipolar doping schemes were investigated for polycrystalline CuGaO2 ceramics through aliovalent cation substitutions on the B-site. Dense, single-phase polycrystalline ceramics were synthesized by solid state reaction through controlling the oxygen partial pressure and quenching to room temperature. The high temperature phase equilibria as a function of oxygen partial pressure was examined through x-ray powder diffraction. These results were compared with thermodynamic calculations of the stability of phases in the Cu-Ga-O system. Electrical measurements were then performed in order verify the carrier type, carrier concentration, and conductivity. Finally, optical measurements were made to establish the optical band gap and transmission window.

Transparent electronics is emerging as one of the most promising technologies for the next generation of electronic products, away from the traditional silicon technology. It is essential for touch display panels, solar cells, LEDs and antistatic coatings. The book describes the concept of transparent electronics, passive and active oxide semiconductors, multicomponent dielectrics and their importance for a new era of novel electronic materials and products. This is followed by a short history of transistors, and how oxides have revolutionized this field. It concludes with a glance at low-cost, disposable and lightweight devices for the next generation of ergonomic and functional discrete devices. Chapters cover: Properties and applications of n-type oxide semiconductors P-type conductors and semiconductors, including copper oxide and tin monoxide Low-temperature processed dielectrics n and p-type thin film transistors (TFTs) – structure, physics and brief history Paper electronics – Paper transistors, paper memories and paper batteries Applications of oxide TFTs – transparent circuits, active matrices for displays and biosensors Written by a team of renowned world experts, Transparent Oxide Electronics: From Materials to Devices gives an overview of the world of transparent electronics, and showcases groundbreaking work on paper transistors

The need for well understood, commercially available p-type transparent conducting oxides for incorporation into basic transparent semiconducting devices alongside their already well understood and available n-type counterparts for application in technologies such as solar cells and capacitive touchscreens motivates this first principles study on the effects of Cu and O vacancies and Mg doping on the intrinsically poor p-type character of CuAlO2, AgAlO2, CuCrO2, and AgCrO2. Density functional theory based calculations using the projector augmented-wave functions along with the generalized gradient approximation to the exchange and correlation energy as implemented by the Vienna Ab Initio Simulation Package are used to study the total crystal energy of the three known polymorphs of CuAlO2 and AgAlO2 in order to determine the most stable polymorph in the ground state. Additionally, three simple magnetic configurations are considered for CuCrO2 and AgCrO2 in the context of total energy of the ground state for the purpose of choosing a specific polymorph and magnetic configuration to be the framework within which the doped and defect systems will be studied. Different functional approaches to the exchange and correlation energies are also considered in order to accurately reproduce the structural properties and the band gap. The 2H delafossite polymorph is determined to be one of the most stable polymorphs and is the focus of this work as it is the least studied of the delafossites. The simple antiferromagnetic configuration is chosen to model magnetic effects in CuCrO2 and AgCrO2 due to it having one of the lowest ground state total energies and also containing the most semiconductor like behavior of the magnetic configurations considered. A 2x2x2 supercell scheme is employed to model 6.25% Cu and Ag vacancies, 3.13% O vacancies, and 6.25% Mg-doping replacing Al and Cr, from which structural properties, electronic properties, hole effective masses, and optical properties are obtained and compared to the pristine crystal in order to offer predictions on the effectiveness of the mentioned native defects and dopant on increasing the conductivity and maintaining transparency in all transparent conducting oxides studied in this work. Comparisons between the results obtained in this work and previous experimental and other theoretical results are made, when available. Many of the properties predicted here are immediately testable via experimentation.

The challenge for producing “invisible” electronic circuitry and opto-electronic devices is that the transistor materials must be transparent to visible light yet have good carrier mobilities. This requires a special class of materials having “contra-indicated properties” because from the band structure point of view, the combination of transparency and conductivity is contradictory. Structured to strike a balance between introductory and advanced topics, this monograph juxtaposes fundamental science and technology / application issues, and essential materials characteristics versus device architecture and practical applications. The first section is devoted to fundamental materials compositions and their properties, including transparent conducting oxides, transparent oxide semiconductors, p-type wide-band-gap semiconductors, and single-wall carbon nanotubes. The second section deals with transparent electronic devices including thin-film transistors, photovoltaic cells, integrated electronic circuits, displays, sensors, solar cells, and electro-optic devices. Describing scientific fundamentals and recent breakthroughs such as the first “invisible” transistor, Transparent Electronics: From Synthesis to Applications brings together world renowned experts from both academia, national laboratories, and industry.