Opportunities and Challenges in Science and Technology of WO3 for Electrochromic and Related Applications (Invited Paper)

Journal Article · Fri Feb 01 00:00:00 EST 2008 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2007.01.026· OSTI ID:950141

Deb, S K

Since the discovery of the electrochromic (EC) effect in transition metal oxides in the mid-1960s, intense research and development work spanning four decades has led to many exciting developments in the science and technology of this class of materials. Tungsten oxide (WO{sub 3}) has emerged as one of the key materials, not only for EC devices, but also for many other related applications. After many years of technology development efforts, WO{sub 3}-based EC 'smart windows' have finally emerged as a viable commercial product. In spite of enormous progress being made on the structural, electrical, and optical properties of amorphous and crystalline WO{sub 3}, a detailed understanding of the EC effect in this material still remains somewhat qualitative. Although theoretical models based on intervalence charge transfer and polaron formation have been widely accepted, these models are still unable to explain some of the experimental results on the coloration phenomena. The coloration in WO{sub 3} is a structure-sensitive phenomenon, and excess electrons can be either localized or delocalized. The presence of structural defects such as oxygen vacancies, impurities, and degree of disorder plays a crucial role in determining the coloration efficiency. Although significant progress has been made in recent years on the calculation of electronic structure and defect properties of both amorphous and crystalline WO{sub 3}, the structural complexity of the material presents many challenges and opportunities for theoretical computation. The unique ability to induce bistable optical and electrical properties in WO{sub 3} by a variety of excitation sources has led to many devices of significant technological interest. Some of the applications currently being pursued include the photoelectrochemical cell for solar energy conversion and storage; photoelectrochemical splitting of water to generate hydrogen; chemical and biological sensors based on the gasochromic effect; photo- and electrocatalysts for a variety of chemical reactions; demonstration of high-temperature (91 K) superconductivity in WO{sub 3} doped with H, Na, and K; synthesis of a new class of hybrid organic/inorganic (WO{sub 3}) materials; and application in ultra-high-resolution electron beam lithography. The emergence of nanostructured WO{sub 3} in recent years will undoubtedly provide new opportunities and significant impact to many of these technologies. This paper presents a brief overview of some of the key research issues the author believes will impact the science and technology of this exciting material.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC36-99-GO10337
• OSTI ID: 950141
• Journal Information: Solar Energy Materials and Solar Cells, Vol. 92, Issue 2, February 2008; ISSN 0927-0248
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
CHEMICAL REACTIONS
COLORATION
DEFECTS
EFFICIENCY
ELECTRICAL PROPERTIES
ELECTROCATALYSTS
ELECTRON BEAMS
ELECTRONIC STRUCTURE
ELECTRONS
EXCITATION
HYDROGEN
IMPURITIES
OPTICAL PROPERTIES
OXIDES
OXYGEN
PHOTOELECTROCHEMICAL CELLS
POLARONS
SOLAR ENERGY CONVERSION
SUPERCONDUCTIVITY
SYNTHESIS
TRANSITION ELEMENTS
TUNGSTEN OXIDES
Basic Sciences
Materials Science and Semiconductors