BELL JAR EXTRACTION TOOL METHOD AND APPARATUS FOR THIN FILM PHOTOVOLTAIC MATERIALS
An apparatus for extracting a bell jar chamber from a processing station of a thin film photovoltaic material is provided. The apparatus includes a rack fixture coupled to a robot loader. The rack fixture is configured to support the bell jar chamber to be moved using the robot loader in a horizontal direction and in a vertical direction. The apparatus further includes at least two support members configured within a vicinity of an upper region of the rack fixture.
This application is a continuation of and claims benefit to U.S. patent application Ser. No. 12/909,563, filed Oct. 21, 2010, which claims priority to U.S. Provisional Patent Application No. 61/254,194, filed Oct. 22, 2009, both of which are hereby incorporated by reference for all purposes.
BACKGROUND OF THE INVENTIONThe present invention relates generally to the manufacture of thin-film photovoltaic modules. More particularly, the present invention provides a method and tool for extracting a supersized chamber used for the manufacture of thin film photovoltaic modules. Merely by way of example, the present invention provides a tool for lifting and extracting a supersized bell jar chamber against gravity load without causing stress-related failure.
Solar energy technology 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 environmentally clean and has been successful to a point, many limitations remain to be resolved before it becomes widely used throughout the world. As an example, one type of solar cell uses crystalline materials, which are derived from semiconductor material ingots. These crystalline materials can be used to fabricate optoelectronic devices that include photovoltaic and photodiode devices that convert electromagnetic radiation into electrical power. However, crystalline materials are often costly and difficult to make on a large scale. Additionally, devices made from such crystalline materials often 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 power. One advantage of the use of thin film technology in making solar cells is to form modules direct on large sized glass substrates. That requires, at the same time, supersized processing system for treating the thin film cells associated with the large sized glass substrates. Additionally, the processing system is subjected to routing maintenance for maintain thin-film process reliability for enhancing solar cell efficiency depending on applications. Often, conventional tools for handing the supersized processing system are either not available or unfit for newly developed system.
From the above, it is seen that improved apparatus and method for handling new supersized processing system for the manufacture of thin-film solar modules are desired.
BRIEF SUMMARY OF THE INVENTIONThe present invention relates generally to the manufacture of thin-film photovoltaic modules. More particularly, the present invention provides a method and tool for handling a supersized processing chamber used for the manufacture of thin film photovoltaic modules. Merely by way of example, the present invention provides a tool for lifting and extracting a supersized bell jar chamber against gravity load without causing stress-related failure.
In a specific embodiment, the present invention provides an apparatus for extracting a bell jar chamber from a processing station of a thin film photovoltaic material. The apparatus includes a rack fixture coupled to a robot loader. The rack fixture is configured to support the bell jar chamber to be moved using the robot loader in a horizontal direction and in a vertical direction. The horizontal direction is normal to the vertical direction. The apparatus further includes at least two support members configured within a vicinity of an upper region of the rack fixture. The two support members have respective arc length regions. The respective arc length regions support at least respective upper inner regions of the bell jar chamber. The rack fixture is in a lifting configuration having the at least two support members to form an intimate contact via a soften material with the upper inner region of the bell jar chamber against all external load. The lifting configuration is associated with a stress indicator of the bell jar chamber to be greater than an intrinsic factor of safety.
In an alternative embodiment, the present invention provides a method for extracting a bell jar chamber with a brittle mechanical characteristic. The method includes providing a rack fixture having at least two support members. Each support member includes an upper edge region. The method further includes inserting the rack fixture including the at least two support members from an open end horizontally into a bell jar chamber along an axial direction of the bell jar chamber. Furthermore, the method includes moving the rack fixture to use the at least two support members to lift the bell jar chamber against a gravitational force for extracting the bell jar chamber from a processing station.
In yet another alternative embodiment, the present invention provides a method for handling a chamber for manufacturing a photovoltaic device. The method includes providing a rack fixture having at least two support members. The method further includes inserting the rack fixture including the at least two support members from an open end into the chamber along an axial direction. Additionally, the method includes raising the rack fixture to form a contact region between each of the two support members and an upper inner region of the chamber. The method further includes lifting the chamber against gravity load and disposing the chamber to a processing station. The processing station includes at least one or more heaters. Furthermore, the method included transferring a substrate bearing a thin-film precursor material into the chamber and sealing the open end of the chamber to create a vacuum condition. The method further includes filling a work gas in the chamber to maintain a predetermined gaseous environment. Moreover, the method includes performing a reactive thermal treatment to the thin-film precursor material in the gaseous environment by supplying thermal energy from the one or more heaters based on a predetermined temperature profile. Through the reactive thermal treatment the thin-film precursor material is transformed to a photovoltaic absorber.
The invention provides the benefit of safely handling a supersized bell jar process chamber of brittle material. The process chamber then can be removed from a manufacturing system for maintenance and replaced by a redundant chamber for substantial saving in process time.
The present invention relates generally to the manufacture of thin-film photovoltaic modules. More particularly, the present invention provides a method and tool for handling a supersized processing chamber used for the manufacture of thin film photovoltaic modules. The invention provides a tool for lifting and extracting a supersized bell jar chamber against gravity load without causing stress-related failure.
Referring to
In a specific embodiment, each of the two support members 320 spread its upper edge to an arc length 321 across the rack fixture 310. In a specific embodiment, the bell jar chamber 300 is made of quartz material to take advantage of its property as a good thermal conductor and an excellent chemical inert matter to be used as a furnace chamber in an application for conducting a reactive thermal process therein. In an implementation, the bell jar chamber 300 is removably installed within a processing station of a thin-film photovoltaic device manufacture system. For example, the tubular shaped bell jar chamber is wholly surrounded by one or more heating elements or cooling elements mounted on an outer shell body. The bell jar chamber is sealed by a cover member engaged with the open end 301. In an example, the bell jar chamber 300 is used for forming a gaseous environment for chemically treating a precursor material on large glass substrates loaded therein to form a thin-film photovoltaic absorber. In order to maintain a large scale manufacture processing within a controlled manner, the bell jar chamber 300, after certain process runs, may be extracted out of the process system for cleaning and other maintenance works while replaced with another cleaned chamber for conducting the manufacture process in the mean time. The quartz material is relatively brittle and may be breakable if the tool for extracting the bell jar chamber 300 causes an internal stress level over certain ranges defined by a minimum factor of safety. In a specific embodiment, the support members for handling the chamber are configured to provide support the bell jar chamber against all external load without causing internal stress level to be near the ranges having high failure (breaking) probability.
In the example shown in
Additionally, the two support members 320 are disposed with a spatial gap 322 between each other. As the tool (or specifically the rack fixture 310) is inserted into the bell jar chamber 300, it should be reached to a preferred position so that when the rack fixture moves up to let the support members 320 to lift the chamber 300 the two support members 320 are respectively located substantially in a vicinity of a balanced position relative to a center of gravity 303 of the bell jar chamber 300. In an embodiment, the value of the spatial gap 322 can be relative flexible within a certain range but correspondingly the preferred position to dispose the rack fixture 310 inside the bell jar chamber must be restricted to a certain spatial range accordingly.
Referring to
The tool as described in above configuration for handling an exemplary bell jar chamber is modeled using a Solidworks™ Simulation software with a simplification of linear force calculation. In this model, the bell jar chamber is selected to be made by quartz material having a density of 2.05 kg/m3. The length of the bell jar chamber is set to be 80 inches and the inner diameter of the tube is set to be 40 inches with a shell thickness of about 18 mm and greater. Based on the material properties as proposed, the model yields an estimation of a tensile strength σT for the specific quartz bell jar chamber to be about 4800 psi and a compressive strength σC to be about 72520 psi. These estimations are comparable with values from Heraeus Brochure: tensile strength σT 40 N/mm2 and compressive strength σC 500 N/mm2, respectively. In order to determine whether the tool is able to handle the target structure without causing any stress related material or structural failure, an internal friction theory, also known as Mohr-Coulomb theory, is applied. Using Mohr-Coulomb theory, a stress-related material failure criterion is defined as:
σ1/σT+σ3/σC<1. (1)
Where σ1 and σ3 are respectively the tensile load and compressive load applied to the target structure. This criterion is used for brittle material with different tensile and compressive properties. Brittle materials do not have specific yield point and hence the yield strength is not recommended for defining limit stresses in this criterion. For designing a reliable tool for handling target structure, a design load (both tensile and compressive) for the target structure is given to provide a safe margin of stress level away from the material limit values. A factor of safety (FOS) can be defined as:
FOS=(σ1d/σT+σ3d/σC)−1 (2)
Here σ1d and σ3d are respectively the design tensile load and design compressive load applied to the target structure. For the bell jar chamber in quartz material a design load is given as 830 psi. This yields a FOS=7.0. In current model, a first principle tensile stress is estimated without considering compressive term and a finite element stress analysis is performed so that the FOS value can be mapped throughout the body of the target structure (though usually only a smaller region is selected for saving in calculation time). In a specific example, two support members 320 are respectively disposed at a position 13 inches and 73 inches from the open end 301; a soften material is also installed in a groove region of the upper edge region of each support member for providing reduction of contact force. A Delrin “O-rings” (which has a linear force deflection characteristic) is used in the model for simplifying the calculation to avoid non-linear solver. The simulation yields a minimum FOS value for this lifting configuration is 18, well above (safer) the minimum FOS 7.0 for quartz material.
Also note that, in an alternative example, the open end 301 of the bell jar chamber 300 has a geometric asymmetric stress effect induced by gravity. The two support members not only should be disposed separately with a proper distance from the center of gravity of the bell jar chamber, but also should be disposed at least a certain preferred distance away from the open end 301 so that the stress level for any local contact region would not surpass the intrinsic tensile/compressive strength of the material. An exemplary analysis shows that with a contact point associated with the back support member at 12 inches closer to the open end 301, the stress at the contact point can be as large as 10000 psi due to the change of the load distribution. This is well above the tensile strength of 5800 psi and most likely will result in tube breaking
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- 1. Start;
- 2. Provide a rack fixture having at least two support members;
- 3. Insert the rack fixture from an open end into the chamber along an axial direction;
- 4. Lift the chamber by using the two support members against respective upper inner regions of the chamber;
- 5. Dispose the chamber to a processing station;
- 6. Transfer a precursor material into the chamber;
- 7. Seal the open end of the chamber;
- 8. Filling a work gas in chamber;
- 9. Perform a reactive thermal treatment to the precursor material to form a photovoltaic absorber; and
- 10. Stop.
As shown, the above method provides a way of handling a chamber for the manufacture of a photovoltaic device according to an embodiment of the present invention. In a preferred embodiment, the method uses a chamber made by quartz material that is inert to the reactive chemical and good in thermal conduction for conducting the desired thermal reactive process therein for forming a photovoltaic absorber material. The chamber can be a tubular bell jar shape and can be also a rectangular cubic shape or other geometries. The chamber can have large size of about 2 meters or greater in length and 1 meter or greater in diameter with about 18 mm or greater in shell thickness.
As shown in
The tool includes a rack fixture having at least two support members provided in step 710. The rack fixture can be associated with a robot loader that is capable of moving linearly, for example, along x-direction horizontally in parallel to an axial direction associated with a tubular shaped target structure. In an embodiment, the rack fixture is an elongated bar structure with a first support member being spaced from a second support member.
The tool further includes the at least two support members on an upper region of the rack fixture. In an embodiment, the rack fixture has a length selected based on the target structure, for example, a tubular shaped bell jar chamber. The length of the rack fixture is at least no shorter than 75% of the length of the bell jar chamber. In another embodiment, one of support members is mounted on a front end of the rack fixture and at least another one is mounted at a position with a predetermined distance from the front end. Depending on target structure geometric shape and material property, the mounting position of the support members can be within a range of distances relative to the target structure. The support member can be in different orientations relative to the elongated rack fixture. In a specific embodiment, the support member is aligned substantially in a plane perpendicular to the length direction of the rack fixture.
Through an open end of the target bell jar chamber, the rack fixture including the at least two support members can be inserted within an inner diameter along an axial direction, as shown in step 720. In an embodiment, the tool is coupled to a robot loader. The robot loader is configured to move horizontally to insert the whole rack fixture into the bell jar chamber which is set on a base support with the bell jar axial direction (e.g, x-direction) in a horizontal direction.
Further, the method 700 includes a step 730 to lift the chamber by using the two support members against respective upper inner regions of the chamber. In a specific embodiment, the same robot loader is used to raise the whole rack fixture upward (e.g., in a y-direction which is normal to the x-direction) such that each support member forms a contact region with the bell jar chamber. In another specific embodiment, the support member is configured to have its upper region being spread laterally with a curved length that is configured to be substantially matched in curvature with the upper inner region of the chamber. Additionally, the upper region of the support member can include a soften material so that the contact region becomes cushioned for reducing stress or at least unidirectional contact forces. For example, a rubber material such as that for O-rings can be installed in a groove region formed in the upper region. This feature may be critical in stress reduction especially between a hard material (the tool) and a brittle material (the chamber). In yet another specific embodiment, the contact region for each support member is within a preferred location range so that lifting the target structure (the chamber) by the two support members would be balanced against the whole external load, which is only a gravitational force for the present implementation. Overall, the lifting of the chamber by the configured tool can be monitored through a stress indicator so that the handling of the chamber by the tool in a specific configuration has a factor of safety substantially higher than a minimum factor of safety associated with intrinsic material property. Therefore, once the lifting step is completed, the chamber is under a stress level that is safe and substantially small in risk of breakage or stress-related failure.
Once the chamber is lifted, the method performs a next step 740 to dispose the lifted chamber into a processing station of a manufacture system for treating thin-film photovoltaic materials. In particular, the processing station is an apparatus for holding the chamber and providing controlled thermal energy to the chamber so that a reactive thermal treatment can be performed to one or more thin-film materials on substrates loaded inside the chamber. This step can be further carried out by using the robot loader to move the bell jar chamber lifted by the two support members of the rack fixture. The bell jar chamber is moved into the processing station which is configured to be surrounded by one or more heaters mounted in a shell structure. The process station also can be equipped with one or more cooling devices for maintaining a balanced thermal energy control. The combined heaters and cooling devices are designed to supply thermal energy to the bell jar chamber and additionally to control chamber temperature following a predetermined temperature profile designated for treating thin-film photovoltaic materials on a plurality of substrates. After disposing the bell jar chamber in the processing station, the tool can be retracted out of the chamber, again controlled by the robot loader in both vertical and horizontal directions.
The method 700 additionally includes step 750 to transfer one or more substrates bearing one or more thin-film precursor materials into the bell jar chamber through the open end. In a specific embodiment, the one or more thin-film precursor materials include copper indium (or gallium) mixture (or alloy) materials pre-deposited on glass substrates. These precursor materials are examples of many material elements used for forming thin-film photovoltaic solar cells.
Referring to
The method 700 further includes filling the chamber with a work gas up to a desired pressure level in step 770. The work gas is designed for react with the precursor material for forming a desired end material product. For example, the work gas includes hydrogen selenide gas mixed with pure nitrogen gas for treating a copper-indium-gallium based precursor thin-film material. The gas filling inlet can be built in the cover member mentioned before.
Furthermore, the method 700 can start step 780 to perform a reactive thermal treatment of the precursor material loaded in the chamber using thermal energy supplied by the one or more heaters following a predetermined temperature profile. The process includes temperature ramping stages and temperature dwelling stages so that the precursor material on the substrates can react with the work gas in the gaseous environment formed inside the heated bell jar chamber. For example, a dwelling stage is set to be at 425° C. for 10-80 minutes. The method 700 may end with step 799 after the precursor material is transformed into a photovoltaic absorber material by the reactive thermal treatment inside the bell jar chamber.
The above sequence of processes or steps provides a handling method for a chamber used for processing a thin-film photovoltaic material according to an embodiment of the present invention. As shown, the method uses a combination of steps including providing a specific tool for safely handling a target structure which is a shaped chamber made by a relative brittle material, disposing the shaped chamber in process system, transferring precursor materials in the shaped chamber, and performing reactive thermal treatment of the precursor materials for the manufacture of the thin-film solar cells.
Although the above has been illustrated according to specific embodiments, there can be other modifications, alternatives, and variations. It is 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.
Claims
1. An apparatus for extracting a bell jar chamber from a processing station, the apparatus comprising:
- a rack fixture; and
- at least two support members positioned proximate an outer surface of the rack fixture, wherein the at least two support members are at least partially characterized along an outer edge by an arcuate shape configured to support the bell jar chamber along an upper inner region.
2. The apparatus of claim 1, further comprising polymeric material overlying each of the at least two support members.
3. The apparatus of claim 2, wherein the polymeric material is selected from a rubber material, an O-ring, or a Delrin Acetal material, wherein the polymeric material is configured to cushion the arc length regions of the support members; wherein the bell jar chamber comprises a quartz material, the bell jar chamber having an axial length of about 200 cm and greater from an open end to a closed end, a diameter of 100 cm and greater, and a shell thickness of about 1.8 cm and greater, the bell jar chamber being characterized by an intrinsic factor of safety of about 7.0 based on Mohr-Coulomb failure theory applied for the quartz material.
4. The apparatus of claim 1, wherein each of the at least two support members are positioned along the rack fixture at a distance from one another of less than or about 140 cm.
5. The apparatus of claim 1, wherein each support member defines a trench within the outer edge characterized by an arcuate shape.
6. The apparatus of claim 5 wherein the trench is characterized by a dovetail shape.
7. The apparatus of claim 6, further comprising an insert positioned between an inner edge of the trench and a gasket at least partially located within the trench.
8. The apparatus of claim 5 wherein a first end and a second end of the outer edge characterized by the arcuate shape comprises a corresponding included angle of about 90 degrees and greater.
9. The apparatus of claim 1 wherein the at least two support members comprise a first support member spaced from a second support member to balance the bell jar chamber about a center of gravity of the bell jar chamber.
10. The apparatus of claim 1 wherein the rack fixture is configured to support the bell jar chamber to maintain a stress level of the bell jar chamber to below a breakage stress of the bell jar chamber by a factor of safety, the factor of safety being defined as an inverse sum of a first ratio of an applied tensile stress over a tensile strength of chamber material and a second ratio of an applied compressive stress over a compressive strength of chamber material.
11. A method for extracting a bell jar chamber, the method comprising:
- providing a rack fixture having at least two support members, each support member comprising an upper edge region;
- inserting the rack fixture including the at least two support members from an open end horizontally into a bell jar chamber along an axial direction of the bell jar chamber;
- interfacing the at least two support members with an inner region of the bell jar chamber; and
- moving the bell jar chamber.
12. The method of claim 11 wherein providing the rack fixture comprises coupling the rack fixture to a robot loader configured to move horizontally and vertically.
13. The method of claim 11 wherein providing the rack fixture having at least two support members comprises disposing a first support member spaced from a second support member by a predetermined distance related at least to a center of gravity of the bell jar chamber.
14. The method of claim 11 wherein each of the at least two support members comprises a groove region formed from a first end to a second end along the upper edge region, the groove region being configured to seat a material for reducing stress level of the bell jar chamber around a contact region between the upper edge region of the two support members and an upper inner region of the bell jar chamber.
15. The method of claim 11 wherein inserting the rack fixture comprises positioning the two support members to respective positions that are substantially balanced relative to a center of gravity of the bell jar chamber and at least a predetermined distance away from the open end of the bell jar chamber.
16. The method of claim 15 wherein the predetermined distance comprises about 15% of an axial length of the bell jar chamber.
17. A method for handling a chamber for manufacturing a photovoltaic device, the method comprising:
- inserting a rack fixture including at least two support members from an open end into the chamber along an axial direction;
- raising the rack fixture to form a contact region between each of the two support members and an upper inner region of the chamber;
- lifting the chamber; and
- disposing the chamber to a processing station.
18. The method of claim 17 wherein the chamber comprises a quartz bell jar having a tubular shape with an open end and a closed end.
19. The method of claim 18 wherein each of the two support members is configured to have the contact region spread laterally with an arc length following the tubular shape of an inner region of the bell jar, the arc length corresponding to an included angle of 90 degrees and greater.
20. The method of claim 19 wherein the inner region of the bell jar is subjected to a contact force substantially smaller than an intrinsic stress strength of the quartz bell jar.
Type: Application
Filed: Aug 19, 2014
Publication Date: Dec 4, 2014
Inventor: Paul Alexander (San Jose, CA)
Application Number: 14/462,866
International Classification: B65G 47/90 (20060101);