Patent Grant
7919400
Not applicable
Not applicable
The present invention relates generally to photovoltaic materials. More particularly, the present invention provides a method and structure for manufacture of photovoltaic materials using a doping process for Group IV materials (e.g., silicon, germanium, silicon-germanium alloys), metal oxides such as copper oxides, metals sulfides and the like. Merely by way of example, the present method and structure have been implemented using a nanostructure configuration, but it would be recognized that the invention may have other configurations.
From the beginning of time, human beings have been challenged to find way of harnessing energy. Energy comes in the forms such as petrochemical, hydroelectric, nuclear, wind, biomass, solar, and more primitive forms such as wood and coal. Over the past century, modern civilization has relied upon petrochemical energy as an important source. Petrochemical energy includes gas and oil. Gas includes lighter forms such as butane and propane, commonly used to heat homes and serve as fuel for cooking. Gas also includes gasoline, diesel, and jet fuel, commonly used for transportation purposes. Heavier forms of petrochemicals can also be used to heat homes in some places. Unfortunately, petrochemical energy is limited and essentially fixed based upon the amount available on the planet Earth. Additionally, as more human beings begin to drive and use petrochemicals, it is becoming a rather scarce resource, which will eventually run out over time.
More recently, clean sources of energy have been desired. An example of a clean source of energy is hydroelectric power. Hydroelectric power is derived from electric generators driven by the force of water that has been held back by large dams such as the Hoover Dam in Nevada. The electric power generated is used to power up a large portion of Los Angeles Calif. Other types of clean energy include solar energy. Specific details of solar energy can be found throughout the present background and more particularly below.
Solar energy generally converts electromagnetic radiation from the sun to other useful forms of energy. These other forms of energy include thermal energy and electrical power. For electrical power applications, solar cells are often used. Although solar energy is clean and has been successful to a point, there are still many limitations before it becomes widely used throughout the world. As an example, one type of solar cell uses crystalline materials, which form from semiconductor material ingots. These crystalline materials include photo-diode devices that convert electromagnetic radiation into electrical current. Crystalline materials are often costly and difficult to make on a wide scale. Additionally, devices made from such crystalline materials have low energy conversion efficiencies. Other types of solar cells use “thin film” technology to form a thin film of photosensitive material to be used to convert electromagnetic radiation into electrical current. Similar limitations exist with the use of thin film technology in making solar cells. That is, efficiencies are often poor. Additionally, film reliability is often poor and cannot be used for extensive periods of time in conventional environmental applications. These and other limitations of these conventional technologies can be found throughout the present specification and more particularly below.
From the above, it is seen that improved techniques for manufacturing photovoltaic materials and resulting devices are desired.
According to the present invention, techniques for manufacture of photovoltaic materials are provided. More particularly, the present invention provides a method and structure for manufacture of photovoltaic materials using a doping process for Group IV materials (e.g., silicon, germanium, silicon-germanium alloys), metal oxides such as copper oxides, metal sulfides and the like. Merely by way of example, the present method and structure have been implemented using a nanostructure configuration, but it would be recognized that the invention may have other configurations.
In a specific embodiment, a method for introducing one or more impurities into a nanostructured material is provided. The method includes providing a nanostructured material having a surface region. The nanostructured material can have a feature size of about 100 nm or less. Examples of such nanostructured material include nanoparticles, nanoporus materials, nano-columns, nanorods, nanotubes, nanostructured thin film and others. The method includes subjecting the surface region to one or more impurities to form a first region having a first impurity concentration within a vicinity of the surface region. The method includes applying a driving force to one or more portions of the nanostructured material to cause the first region to form a second region having a second impurity concentration.
In an alternative embodiment, an alternative method for introducing one or more impurities into a nanostructured material is provided. The method includes providing a substrate characterized by one or more impurities having a first impurity concentration. The substrate includes a surface region and a thickness. The method includes depositing a nanostructured material overlying the surface region of the substrate. The method includes subjecting the nanostructured material and/or the substrate to a driving force to form a first region in the nanostructured material having a second impurity concentration.
Many benefits are provided by ways of embodiments of the present invention. In particular, embodiments according to the present invention provide a method and structures for a nanostructured material having desirable impurity characteristics. Examples of desired characteristics include n or p type doping, controlled resistivity, controlled carrier density, controlled carrier mobility, and so forth. The method has been applied to fabrication of photovoltaic cells. But it should be recognize that embodiments according to the present invention have a much broader range of applicability.
According to the present invention, techniques for manufacture of photovoltaic materials are provided. More particularly, the present invention provides a method and structure for manufacture of photovoltaic materials using a doping process for Group IV materials (e.g., silicon, germanium, silicon-germanium alloys) metal oxides such as copper oxides, metal sulfides and the like. Merely by way of example, the present method and structure have been implemented using a nanostructure configuration, but it would be recognized that the invention may have other configurations.
Referring to
Depending on the embodiment, a precursor to the nanostructured material may be provided. The precursor to the nanostructured material may be provided in a solid form, for example as a powder. Alternatively, the precursor to the nanostructured material may be provided as a colloid or a slurry suspended in a suitable medium. The method includes adding one or more impurities to the precursor to the nanostructured material to form the first region having a first impurity concentration. The one or more impurities may be distributed over the precursor to the nanostructured material. Alternatively, the one or more impurities may be allowed to intermix with the precursor to the nanostructured material.
In a specific embodiment, after the one or more impurities are added to the nanostructured material, the combination of materials is subjected to a driving force 402 as illustrated in
As illustrated in
In a specific embodiment, the present invention provides a nanostructured photovoltaic material. In a specific embodiment, the nanostructured material can be a Group IV material. Examples of the Group IV material include silicon or germanium, silicon-germanium alloys, and others. The nanostructured material can be a compound semiconductor such as a III-V material or a II-VI material. The nanostructured material can also be metal oxides such as ZnO, CuO, Cu2O, Fe2O3, Fe3O4, TiO, TiO2, SnO2, SnO, WO3 and others. The nanostructured material can also be metal sulfides such as ZnS, Cu2S, FeS2, FeS, SnS, SnS2 and others. Of course there can be other variations, modifications, and alternatives.
Optionally, before depositing the nanostructured material, the substrate may be subjected to a cleaning process to clean at least the surface region using one or more techniques. In a specific embodiment, the cleaning process can include a wet and/or dry cleaning technique. Examples of such wet cleaning technique include, among others, an RCA clean, a wet dip, an organic wash with solvents such as acetone and/or alcohols, such as isopropyl alcohol, ethanol, any combinations of these and the like. The cleaning process can also include ultra clean water such as deionized water and/or substantially particle free water. In other embodiments, the cleaning process can include a plasma clean using oxygen and/or inert gas species, such as nitrogen, argon, and other suitable gases, and the like. Once cleaning has occurred, the surface region is substantially free from particulates, organic contaminants, metals, and other chemicals, including combinations of these. Of course, one of ordinary skill in the art would recognize other variations, modifications, and alternatives.
Referring to
In a specific embodiment, the nanostructured material may be nanoparticles provided in a solution or as colloidal particles suspended in a liquid or a gel. In an alternative specific embodiment, a precursor to the nanoparticles can be used. The precursor to the nanoparticles is preferably converted into the nanostructured material with desired feature size and characteristics. Examples of precursors include chemical precursors that may be converted to the desired nanostructured material by way of a chemical, photochemical, or electrochemical reaction, a combination of these, or the like. The solution or the gel, for example, comprising the precursor to the nanostructured material can be deposited on the surface region of the substrate 600 and allowed to distribute over the surface using many techniques known in the art. In a specific embodiment, the solution or the gel comprising the precursor to the nanostructured material can be deposited on the surface region of the substrate 600 using a spin on technique known in the art. Alternatively, the solution or the gel comprising the precursor to the nanostructured material can be sprayed on the surface region of the substrate 600, also known in the art. Yet alternatively, the substrate 600 can be dipped into a solution comprising the nanostructured material or a precursor to the nanostructured material also known in the art. Yet alternatively, the solution or the gel comprising the precursor to the nanostructured material can be doctor bladed on the surface region of the substrate 600, also known in the art. Of course there can be other variations, modifications, and alternatives.
As shown in
In an alternative embodiment, the one or more impurities may be provided in a solid state 802 as shown in
Alternatively, the one or more impurities may be provided as a fluid. For example, the one or more impurities may be provided as a solution, a colloid or a slurry suspending in a suitable medium. In a specific embodiment, the one or more impurities are allowed to distribute over a surface of the nanostructured material, which has been formed on the surface region of the substrate. The solution comprising the one or more impurities may be spun on, sprayed on, cast on, or doctor bladed on an exposed surface of the nanostructured material. Alternatively, the nanostructured material overlying the substrate may be dipped into a solution comprising the one or more impurities.
In a specific embodiment as shown in
As illustrated in
Referring to
It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
This application claims priority to U.S. Provisional Patent Application No. 60/948,754, filed Jul. 10, 2007, entitled “METHODS FOR DOPING NANOSTRUCTURED MATERIALS AND NANOSTRUCTURED THIN FILMS” by inventor Howard W. H. Lee, commonly assigned and incorporated by reference herein for all purposes.
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