Surface science, solar materials

The three phases of interest are the solid (S), liquid (L), and gas (G) phases, none of which is infinite. The boundary region between the S, L, and G phases has fundamentally different properties from the bulk. The S/S, S/G, and S/L surfaces, in that order, are of greatest interest to the solar materials scientist (4). Some of the broad topical areas of study at the interfaces of SECS are listed in Table 2. An understanding of these topics is enhanced by applying the methodologies of interface science. 

In this section, an overview will be provided of the topical areas of surface science research that are especially important to solar energy technologies. These comments are based in part on a report from a workshop held in July 1980 (4). Broad areas of surface science that affect solar materials research are indicated. 

Table 1 of a paper by Murr (2) lists problems and/or concerns related to specific interface materials and specific components of SECS. In Table 2 of the same work, he related topical study areas and/or research problems to S/S, S/L, S/G, L/L, and L/G interfaces. It is also useful to divide interface science into specific topical areas of study and consider how these will apply to interfaces in solar materials. These study areas are thin films grain, phase, and interfacial boundaries oxidation and corrosion adhesion semiconductors surface processes, chemisorption, and catalysis abrasion and erosion photon-assisted surface reactions and photoelectrochemistry and interface characterization methods. The actual or potential solar applications, research issues and/or concerns, and needs and opportunities are presented in the proceedings of a recent Workshop (4) and summarized in a recent review (3). 

Dye sensitization of electrodes is an old area of science with a rich history. The field has experienced renewed interest owing to the development of high surface area colloidal semiconductor electrodes. These materials yield impressive solar conversion efficiencies when employed in regenerative solar cells that have already found niche applications and have the real possibility of replacing traditional solid-state photovoltaics. Thus for the first time in history a solar cell designed to operate on a molecular level is useful from a practical point of view. It is also likely that other applications in the growing areas of molecular photonic materials will arise. 

Thomas Russell is Silvio O. Conte Distinguished Professor, Polymer Science and Engineering Department Director, Energy Frontier Research Center (EFRC), Polymer-Based Materials for Harvesting Solar Energy. His research interests are polymer-based nanoscopic structures, polymer-based nanoparticle assemblies, electrohydrodynamic instabilities in thin polymer films, surface and interfacial properties of polymers, polymer morphology kinetics of phase transitions, and supercritical fluid/polymer interactions. 

G. A. Niklasson and C. G. Granquist, Surfaces for selective absorption of solar energy an annotated bibliography, 1955-1981, Journal of Materials Science, 18,3475-3534 (1983). 

Accurate measurements of the spectral reflectance of diffusing surfaces are important to numerous scientific and engineering disciplines, including the fields of solar energy materials, color science, analytical chemistry, spacecraft thermal engineering, military low observable materials, and remote... 

A final class of materials is the optically transparent electrodes based on metal oxides (e.g., indium-tin oxide, ITO). These materials are very popular in the field of energy conversion, as a support for Dye-Sensitive Solar Cells, but the group of Heinemann developed at the end of the 1990s a spectroelectrochemical sensing method based on such transparent electrodes. The method is defined as the coupling of an electrochemical detection with a spectroscopic analysis." " This approach allows for multimode selectivity and is usually applied in the presence of surface modification for preconcentration of the analyte. More recently, porous and optically transparent electrodes have been prepared and applied for combined spectroscopic and electrochemical analysis" " which should lead in a near future to further developments in analytical sciences applied to the environment. 

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