BRIEF DESCRIPTION OF THE FIGURES
The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.
FIG. 1 is a flow chart of conventional CVD operations that use a petroleum based plastic substrate.
FIG. 2 is a flow chart of the improved CVD process using a bio-based plastic substrate.
FIG. 3 is a cross sectional view of thin film solar cells based on a petroleum based substrate.
FIG. 4 is a cross sectional view of thin film solar cells manufactured using a bio-based plastic substrate.
FIGURES—REFERENCE NUMERALS
10. Bio-Based Substrate Thin Film PV Cell and Method of Creation
11. Transparent Conductive Coating
12. Anti-reflection Coating
13. N-type “Window” Layer
14. P-type “Absorber” Layer
15. Ohmic Contact
16. Petroleum Based Substrate
17. Silicone Oxide Coating
18. Bio Based Substrate
DETAILED DESCRIPTION
Referring to the illustrations, a preferred embodiment of a method for building thin film flexible solar cells on bio-based plastic substrates is illustrated and generally indicated as 10 in FIGS. 2 and 4. The method allows thin film flexible solar cells to be built on bio-based plastic substrates.
Referring to FIG. 1, the conventional process of low temperature chemical vapor deposition (CVD) is shown. In the first step, the petroleum based substrate is degassing at 150 degrees Celsius. After degassing, the ohmic contact layer is deposited. Following these processes, the P-type and N-type layers are deposited. Finally a transparent conductive coating is deposited, forming the top layer of the film.
Referring to FIG. 2, the improved process of the present invention, of low temperature CVD on a bio based plastic substrate is shown. In this improved process, the bio-based substrate is degassed at approximately 120 degrees, however after this step, a coating of silicon oxide is deposited on both sides of the substrate. The bio-based substrate is made from Poly Lactic Acid (PLA); a material generated from corn dextrose, which is fermented, then process into lactide and finally polymerized into PLA. Silicon oxide is used as the coating since it is a non-conductive material, which has been used successfully as a barrier layer in CVD processing and is compatible with PLA.
After the silicon oxide coating is applied, the substrate surface is cured to improve cross linking between the silicon oxide and the substrate. The silicon oxide reacts with oxygen to form free radicals that can cross link the silicon oxide and the bio-based substrate. The approximate curing time for this process is around ten minutes. Once the substrate is cured, the ohmic contact layer, P-type and N-type layers, anti-reflective coating and transparent coating are applied in the same manner as a typical petroleum substrate based CVD application.
Referring to FIG. 3, a cross section of a conventional thin film solar cell is depicted. The cell consists of a petroleum based substrate on which the ohmic contact is placed. The P-type absorber layer is applied on the ohmic contact layer, and covered with the N-type window layer. Thereafter an anti-reflective coating and finally a transparent conductive coating are applied.
By contrast, referring to FIG. 4, a cross-section of the improved bio-based thin film substrate solar cell is shown. In this preferred embodiment, a bio-based substrate comprising a proprietary third party plastic is used. The bio-based plastic is coated on both sides with a silicon oxide film. The thickness of the plastic and silicon oxide coating can function at a range of between 12.7 to 254 microns, but about 50.8 microns for thin film PV applications is preferred. Once the substrate surface has cured, the same layers comprising an ohmic contact layer, a P-type absorber layer, N-type window layer, anti-reflective coating, and a transparent conductive coating are applied. The resulting solar panel has all of the advantages of a typical petroleum based substrate thin film photo voltaic, without relying on petroleum, petroleum derivatives, or other non-renewable sources for its construction.
All features disclosed in this specification, including any accompanying claims, abstract, and drawings, may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. §112, paragraph 6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C. §112, paragraph 6.
Although preferred embodiments of the present invention have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.
Patent Application
20070295394
