NON-TECHNICAL DESCRIPTION: Transparent conductors are a critical component in many technologies affecting society, including solar cells, touch screens, flat panel displays, light emitting diodes and lasers. Finding materials that combine high electrical conductivity with excellent optical transparency in the visible spectrum has proved challenging: metals typically are good conductors but reflect rather than transmit visible light, while insulators like glass are highly transparent but do not carry an electrical current. The goal of this project is to pursue an unconventional paradigm, developed in previous work by members of the project team, to discover and develop new transparent conducting materials based on earth-abundant elements that exhibit substantially better performance and can be made with lower cost than the long-standing industry-standard indium-tin-oxide (ITO). Theoretical analysis combining mining of databases of materials property measurements and computations with predictive simulations of the structure and properties of candidate materials will be closely integrated with efforts in the laboratory to synthesize, characterize and optimize real materials. In the context of the Materials Genome Initiative coordinating efforts across the nation to accelerate the discovery, development and deployment of advanced materials, tools and techniques for integration of theory and experiment in materials design that are developed in the course of the project will be made available to the community to advance progress in broader materials design challenges. Breakthroughs in the development of transparent conductors will advance green technologies for energy generation, lighting, and passive building designs.
TECHNICAL DESCRIPTION: The conventional paradigm to combine the contradicted properties of transparency and high electrical conductivity is to heavily dope a wide band gap ? thus transparent ? semiconductor to increase its electrical conductivity. Rather than making a transparent semiconductor more conductive, the idea of the new paradigm is to make a metal optically transparent. This can be done by increasing the electron effective mass by correlation effects, which reduces the metal reflectivity in the visible range, in targeted systems for which interband transitions are above the visible range. The design space for the discovery of new transparent conductors spans a wide range of families, including correlated oxides, layered chalcogenides, pnictides, and intermetallic compounds. A hierarchical three-level search approach will be pursued. First, material candidates will be pre-screened in the available materials design space using simple-to-apply qualifier criteria, followed by high-throughput first-principles computations of crystal structure, electronic bands, and quantities related to optical and electrical transport properties at the level of density functional theory (DFT). At the third level, correlation effects will be studied within density functional mean field theory (DMFT) to refine the lower level search criteria and identify the most promising systems for further investigation. In the laboratory, synthesis and characterization of the electrical transport and optical properties of these candidate materials and comparison with theoretical predictions will aid in the refinement of design principles and the expansion of the set of transparent conducting materials available for technological applications.
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