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Thin films are thin material layers ranging from fractions of a nanometre to several micrometres in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction.
Some work is being done with ferromagnetic thin films as well for use as computer memory. It is also being applied to pharmaceuticals, via thin film drug delivery.
Ceramic thin films are also in wide use. The relatively high hardness and inertness of ceramic materials make this type of thin coating of interest for protection of substrate materials against corrosion, oxidation and wear. In particular, the use of such coatings on cutting tools may extend the life of these items by several orders of magnitude.
The engineering of thin films is complicated by the fact that their physics is in some cases not well understood. In particular, the problem of dewetting may be hard to solve, as there is ongoing debate and research into some processes by which this may occur.
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Physical vapor deposition
Physical vapor deposition (PVD) refers to a variety of vacuum deposition techniques that deposit thin films by the condensation of vaporized material onto a substrate. The coating material can be evaporated thermally, or by laser or electron bombardment. PVD can be used to deposit metals, alloys, ceramics, composites and multilayers.
PVD techniques
- Thermal Evaporation
- Electron beam physical vapor deposition
- Sputtering
- Pulsed laser deposition
- Cathodic Arc Deposition
Chemical vapor deposition
Chemical vapor deposition (CVD) uses vapor phase chemical reaction to deposit thin film on a substrate.
CVD techniques
- Chemical vapor deposition
- Plasma Enhanced Chemical Vapor Deposition (PECVD) is generally applied to deposit the antireflection film layer and is one of the most critical processes to increase efficiency. Sputtering technology is generally applied to deposit TCO (Transparent Conductive Oxide) and back contact (aluminum etc.) layers. These depositions take place in vacuum chambers 1.
- Metalorganic chemical vapor deposition
- Hybrid Physical-Chemical Vapor Deposition
Transparent electronics
A new class of thin film inorganic oxid materials (called amorphus heavy-metal cation multicomponent oxide) which could be used to make transparent transistors that are inexpensive, stable, and environmentally benign 2.
Batteries
There are thin-film batteries.3
Thin Films Solar Cells
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- Further information: Low cost solar cell, Third generation solar cell, and Thin Films Solar Cells
Thin-film technologies are also being developed as a means of substantially reducing the cost of photovoltaic (PV) systems. The rationale for this is that thin-film modules are expected to be cheaper to manufacture owing to their reduced material costs, energy costs, handling costs and capital costs, specially represented in the used of printed electronics processes.
Thin-films solar cells consist of plastic or other substrates coated with silicon (i.e. amorphous silicon) or other photovoltaic material.
These technologies face major technical hurdles. Laboratory tests have shown efficiencies of up to 19.9 percent for CIGS cells, compared with a record of about 16.5 percent for cadmium telluride. But the reality outside of the labs (commercial photovoltaic panels) has been different. So far, First Solar has reached average cell efficiencies of 10.6 percent.4
Research
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Research Institutes and Universities involved with thin film photovoltaic technologies:5
- Avanced technology Institute - University of Surrey (UK)
- AIST - National Institute of Advanced Industrial Science and Technology
- Arizona State University
- Colorado State University
- École Polytechnique Fédérale de Lausanne
- Florida Solar Energy Centre
- Fraunhofer ISE
- Helsinki University of Technology (TKK)
- IMEC
- Imperial College London
- Idaho National Laboratory (INL)
- KAIST - Korean Advanced Institute of Science and Technology
- Lawrence Berkeley National Laboratory
- Massachusetts Institute of Technology (MIT)
- National Renewable Energy Laboratory (NREL)
- University of Delaware - Institute of Energy Conversion (IEC)
Materials
Light-absorving materials in thin-film photovoltaic cells are:
- Cadmium telluride (CdTe)
- Copper indium (gallium) (di)selenide (CIS and CIGS)
- Dye
- Organic materials.
- Silicon:
- Amorphous silicon and nanocrystalline silicon (that can be combined in micromorphous silicon).
- Black silicon
Production
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Thin-film solar cell manufacturing is poised to make a giant leap in scale with the birth of the gigawatt fab 6. First Solar (CdTe) is the largest manufacturer of thin-film cells in the world7, with production capacity expected to reach over 500 MW by the end of 2008.
- BP Solar (amorphous silicon, cadmium telluride)
- Energy Photovoltaics (amorphous silicon, copper indium gallium diselenide)
- Global Photonic Energy (organic photovoltaics)
- Odersun with the capacity to produce 30 megawatts of thin films.
- Next Solar, would start production at its first thin-film solar factory -- a 30-megawatt plant using Oerlikon Solar equipment -- early 2009.
- Sharp Corp. expects to begin production at a 1-gigawatt thin-film plant in Japan in 2010.
- Siemens Solar (copper indium diselenide)
- Signet Solar (amorphous silicon) said it would start production at its first plant, also in Germany, in the third quarter of 2008 this year and would build its second plant in India.
- Quantum Solar Systems (quantum dot polymer solar cells) 8.
High precision thin film deposition on large substrates
One of the major barriers met in thin film deposition is the ability to coat large dimension substrates whilst obtaining high precision results with mono or multi-layer deposition.
The HiTUS plasma sputter deposition technology together with the Linear Target technology has demonstrated major improvements in desired results such as precision, uniformity, stress control from compressive to tensile with zero in between, and roughness on substrates measuring up to and over and above 50 to 60 cm. The Linear Target also enables the development of a large area linear process with the same advantages as HiTUS for roll-to-roll or in-line processes.
Other techniques
- Atomic Layer Deposition (ALD)
- Carbon nanotubes in photovoltaics
- Copper indium gallium selenide (CIGS)
- Chemical vapor deposition
- Electrophoretic deposition
- Lamination
- Molecular beam epitaxy
- Sol-Gel Process
- Spin coating
- Sputter deposition
- Transparent photovoltaics
See also
- Bioplastic
- Building integrated photovoltaics (BIPV)
- Cost-per-watt
- Ellipsometry
- Flexible photovoltaics
- Gigawatt fab
- Glass transfer system
- Hydrogenography
- Junction
- Laser scribing
- Printed electronics
- Thin-film optics
- Thick film
References
- ^ http://www.omron-semi-pv.eu/en/pv-thin-film/pv-thin-film/vacuum-process.html
- ^ http://www.eurekalert.org/pub_releases/2004-12/osu-mam122804.php
- ^ http://www.sciengineeredmaterials.com
- ^ http://www.greentechmedia.com/articles/heliovolt-hits-122-efficiency-885.html
- ^ Printed and Thin Film Photovoltaics and Batteries: IDTechEx
- ^ http://www.pv-tech.org/featured_articles/_a/first_edition_challenges_of_the_gigawatt_fab/
- ^ http://www.greentechmedia.com/articles/thin-film-solar-to-reach-42-gw-1372.html
- ^ http://qsolarsystems.com
External links
- Thin-Film Solar Has Bright Future.
- Thin-Film Solar Set to Take Market Share From Crystalline Solar PV: worldwide thin-film solar production will grow eightfold by 2010, with amorphous silicon leading the way.
- The Thin Film Solar Revolution
Wikipedia content modification information:
- This page was last modified on 26 November 2008, at 13:30.
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