| Thin-film solar cell -> Monitor Keywords |
|
|
 
Thin-film solar cellRelated Patent Categories: Batteries: Thermoelectric And Photoelectric, Photoelectric, Cells, Copper, Lead, Or Zinc ContainingThin-film solar cell description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060180200, Thin-film solar cell. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL AREA [0001] The present invention relates to a thin-film solar cell without cadmium, to a method and production line for manufacturing such cells. BACKGROUND OF THE INVENTION [0002] Solar cells provide a means to produce electric power with minimal environmental impact because it is a renewable technology. In order to become a commercial success the solar cells need to be efficient, to have low cost, to be durable, and not add other environmental problems. [0003] Today's dominant solar cell technology is based on crystalline silicon. It fulfils many of the requirements mentioned above but can not be produced at such low cost that electricity generation in large scale is cost effective. It also requires relatively large amount of energy in the production, which is an environmental disadvantage. [0004] Solar cells based on thin film technologies have been developed. They offer a potential of substantial cost reductions but have, in general, lower conversion efficiencies and less good durability. A very promising thin film solar cell technology is based on the semiconductor Cu(In,Ga)Se.sub.2, abbreviated CIGS, which has demonstrated high efficiencies (16,6% in small prototype modules [1]) and durability in operation. It remains to demonstrate low cost in real production. [0005] CIGS-solar cells are thin-film solar-cells with a CIGS-layer serving as absorber of sunlight. Electron-hole-pairs are generated therein. [0006] A typical CIGS-solar cell is shown in FIG. 1 and comprises a glass substrate 1 with a thickness of 2-3 mm, an Mo-back contact 2 with a thickness of 0,5-1 .mu.m, a CIGS-layer 3 of 1,5-2 .mu.m, a CdS buffer layer 4 with a thickness of 50 nm and a ZnO window layer 5 of 0,5-1 .mu.m. An optional second buffer layer 6 may be present between the CdS buffer layer and the window layer and has a thickness of 50 nm. [0007] The CIGS-layer is a Conductive Cu(In,Ga)(Se,S).sub.2 compound. The CdS buffer layer serves as protection of the CIGS-layer. The window layer is a n-type conductive doped zinc oxide layer. With the CIGS-layer it forms a pn-junction and serves as a transparent front contact. The optional second buffer layer comprises non-doped ZnO. Presently its role is not fully understood. Statistically seen, solar cells with this second buffer layer exhibit better properties compared to cells with a single ZnO-layer. [0008] The commonly used way of fabricating CIGS solar cell modules include formation of a pn-junction and front contact according to the following: (1) a buffer layer (typically 50 nm of CdS) is deposited by chemical bath deposition (CBD), (2) a high resistivity thin layer of ZnO is deposited on top of the CdS layer by sputtering, (3) the layered structure is patterned by mechanical scribing to open contacts for the serial interconnects, (4) a front contact of a transparent conductive oxide (TCO) is deposited, and (5) an additional patterning step of mechanical patterning as part of the interconnect structure. [0009] EP-A2-0 838 863 discloses a thin-film solar cell fabricated on a glass substrate. The solar cell comprises a metallic back electrode, a light-absorbing layer having on its surface a Cu(InGa)(Se).sub.2 layer (CIGS layer), an interfacial layer referred to as a buffer layer, a window layer and an upper electrode. The back electrode is a p-type semiconductor and the window layer is an n-type semiconductor. Between the back and upper electrodes an open circuit voltage in the order of 0,2-0,8 V is obtained when the solar cell is hit by light. Electrical current will be generated in the p-n junction between the p- and n-layers. [0010] The buffer layer comprises a group II-VI compound semiconductor containing hydroxyl groups. An exemplary compound is Zn(O,S,OH).sub.2. [0011] DE 44 40 878 C2 discloses a thin-film solar cell comprising a glass substrate, a back electrode, a light absorbing layer, a front buffer layer and a window layer. The front buffer layer comprises a mixture of In(OH).sub.3 and In.sub.2S.sub.3 and is applied in a wet process or a chemical vapour deposition process (CVD) with organo metallic compounds or with atomic layer epitaxy deposition process (ALE). The novel concept here is that the buffer layer does not contain cadmium. [0012] To fabricate the solar cell with chemical wet process steps mixed with sputtering makes the solar cell less attractive for large scale production. To fabricate the solar cell wet processes are mixed with the co-vapour deposition process which renders the structure less attractive for large scale production. [0013] An example of thin-film solar cells using a first CdZnS buffer layer between a CIGS-layer and a window layer is disclosed in U.S. Pat. No. 5,078,804. A second ZnO buffer layer on top of the first buffer layer and in contact with the window layer is also provided. The first CdZnS buffer layer comprises two layers, a high Zn content CdZnS layer on top of a low Zn content CdZnS layer, both of which are applied using an aqueous solution method. The second ZnO buffer layer also comprises two layers, a low resistivity ZnO layer on top of a high conductivity ZnO layer both of which are applied using sputtering in an argon or oxygen/argon atmosphere. [0014] To manufacture the solar cell with chemical wet process steps mixed with sputtering makes the solar cell less attractive for large scale production. The use of toxic cadmium makes the cell less attractive for environmental reasons. Also handling and disposal of the hazardous wastes are costly. [0015] U.S. Pat. No. 5,948,176 discloses a solar cell structure comprising a first active CIGS layer on top of a metal back contact. On top of the CIGS layer a buffer layer of n-type conductive doped ZnO layer is deposited by a wet process using a zinc chloride solution as doping source. A second active layer comprising ZnO is deposited on the buffer layer. The second active layer comprises a first high resistive ZnO layer and a second low resistive ZnO layer on top of which a grid of front face electrodes is sputtered. [0016] Another example of a cadmium containing solar cell is shown in U.S. Pat. No. 4,611,091. SUMMARY OF THE INVENTION [0017] One object of the invention is to reduce the number of process steps for the manufacture of the solar cell, thereby reducing the cost involved in their manufacture. [0018] Another object of the invention is to replace the toxic CdS-layer with more environmental-friendly compound. [0019] Still another object of the invention is to replace the CdS-layer with a material that absorbs less of the incident light than does a CdS-layer, thereby increasing the amount of light impinging the under-laying CIGS-layer and accordingly increasing the photo current generated by the cell. [0020] A further object of the invention is to replace the wet process for manufacture of the CdS-buffer layer with a novel process that allows for integration with the preceding (dry) vacuum deposition of the CIGS-layer and/or integration with the following (dry) sputter deposition of the high resistivity ZnO window layer. [0021] These objects are achieved with a thin-film solar cell indicated in the preamble of claim 1, a method of producing an interfacial layer in accordance the preamble of claim 7 and a process line for manufacturing a solar cell structure in accordance with the preamble of claim 14. The characteristic features of the invention are indicated in the characterizing clause of claims 1, 7 and 14 respectively. Continue reading about Thin-film solar cell... Full patent description for Thin-film solar cell Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Thin-film solar cell patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Thin-film solar cell or other areas of interest. ### Previous Patent Application: Photosensitive organic semiconductor compositions Next Patent Application: Piston-activated valve and methods and apparatus for restraining free play in a device Industry Class: Batteries: thermoelectric and photoelectric ### FreshPatents.com Support Thank you for viewing the Thin-film solar cell patent info. IP-related news and info Results in 0.67171 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
