Solar cells based on zinc and tin sulfide compounds
Development of new technology for creation of thin film solar cells on base zinc and tin sulfides
Tech Area / Field
- INF-ELE/Microelectronics and Optoelectronics/Information and Communications
- MAT-SYN/Materials Synthesis and Processing/Materials
- NNE-EPP/Electric Power Production/Non-Nuclear Energy
- NNE-SOL/Solar Energy/Non-Nuclear Energy
3 Approved without Funding
Sokolsky Institute of Organic Catalysis and Electrochemistry, Kazakstan, Almaty
- Institute of Physics and Technology, Kazakstan, Almaty
- Sheffield Hallam University / Materials and Engineering Research Institute, UK, Shiffield\nFlorida Solar Energy Center, USA, FL, Cocoa
Project summaryThe Project aim. Within the framework of this project it is planned to demonstrate new concept and enhanced performance for SnSX and Cu2SnZnS4 thin film solar cells (TFSC) on flexible, nanostructured metal substrates and superstrates to provide the basis for further efficiency improvements in the solar module production and to develop new device concepts enabling cost reductions on the long term using relatively abundant materials, as well as environment and human health friendly design and fabrication technologies.
Current status. One of the major hurdles for photovoltaic to become more popular is the fact that the price of the electricity (cost per watt) produced by solar modules in most cases is not yet competitive with that produced by conventional methods. The cost can be reduced by either improving efficiency or reducing the production costs of photovoltaic modules. Recent interest in thin film photovoltaic is primarily due to improvements in conversion efficiency of cells and effective lowering of the manufacturing costs compared to expensive crystalline and polycrystalline silicon technology. Thin film solar cells based on the use of CuIn(Ga)Se2 and CdTe absorber materials have been produced with efficiencies of 20% and 16.5%, respectively. These results clearly indicate that high efficiency solar cells can be achieved using polycrystalline materials. However, these technologies demand careful research and have limitations. For example, it is well known that the lack of abundance of expensive In and Ga may limit the large scale use of chalcopyrite-based technology. There is a need to search for other materials that can be used to produce thin-film elements. Such candidates are SnSX and Cu2SnZnS4 with a direct optical energy band gap of 1.2 – 1.7 eV, close to the optimum value required for efficient light absorption and it exhibits p-type electrical conductivity with absorption coefficient as high as 104 cm-1. The constituent elements of these compounds are non-toxic and abundant in nature. The main argument, served as a prerequisite for the production of this work was the wide industrial production of raw materials (components), their large reserves in nature and, accordingly, a low price. The comparative data on volumes of production of copper, tin, zinc and sulfur in comparison with the indium and gallium, silicon show a distinct advantage in price and availability of Cu, Sn, Zn, S for the manufacture of solar cells: gallium - 30 tons, indium - 75 tons, selenium - 600 tons, copper -15,000,000 tons, tin - 165 000 tons, zinc - 12.5 million tons, sulfur - 54 million tons, silicon (electronic quality) - 5000 tons. Theoretical studies show’s that new semiconductor materials can achieve conversion efficiency of solar radiation 25%.
The project’s influence on progress in this area. Theme is rather actual for the development of energetic during the period of decreasing of stocks and growth in oil prices expected after 2015-2020. The Project contributes to the development and application of renewable ecologically clean energy sources. The development of alternative energy based on the use of joint scientific research of the two institute of Kazakhstan will provide the creation of innovative productions in this field. Competing in the global market is now formed only for the producers of silicon cells. Manufacture of thin-film solar cells does not yet have a large scale and is now quite competitive in the general market of solar converters due to the low cost in production. Kazakhstan, with sufficient raw materials, industrial, scientific and technical potential, has good prospects for the creation of programs for the development of solar energy. Kazakhstan has sufficient resources of solar energy. The duration of sunshine is 2200-3000 h/year, while solar energy is 1300-1800 kVt/m2/year. Energy Strategy of the Republic of Kazakhstan is aimed at increasing the use of nontraditional, first of all renewable resources, including solar energy. Currently, the demand for solar inverters is covered in Kazakhstan by imported expensive silicon cells manufactured in China (Firm Sun Oasis). Ukrainian company "Quasar" offers often do not conform to the requirements both in quality and efficiency of silicon batteries at a price of $ 1000 per kW. On the basis of the proposed project is expected to develop technical decisions for the creation our own production of thin-film solar cells by the effective price of $ 500 per kW.
The participants’ expertise. The scientists taking part in the project have significant experience in photovoltaic confirmed by their publications, participation in the international conferences and successful performance of ISTC projects (ISTC - B 529, ISTC-K-1342). This information is available on the Internet web-sites http://www.istc.ru/.
Expected results and their application. The research and development of the solar cell that composes of abundant materials without using any rare metals are important in Kazakhstan as a country with huge areas which need in autonomic energy sources.. The implementation of this Project will lead to techniques will be used to allow the industrial production of high-efficiently thin film solar cells in Kazakhstan. The TFSC will find application especially in areas where there are difficulties with the delivery of electricity through a permanent network
Meeting the ISTC goals and objectives. The implementation of this project involved the former "weapons" scientists of Institute of Physics and Technology in Kazakhstan. This republic support the program "Global Initiatives for Proliferation Prevention» (GIPP) U.S. Department of Energy designed to a peaceful development. The project meets the objectives of the ISTC. Adherence to these objectives can be attained by planned wide involvement of scientists and participating institutions into international scientific community through providing information on the Project during international conferences and workshops.
Scope of activities. The following activities will be implemented under the Project:
- determined the concepts for creating new designs of SnSX and Cu2SnZnS4 thin film solar cells (TFSC) on flexible, nanostructured metal substrates and superstrates with direct and reverse position of layers in the structure of the substrate;
- carrying out the experimental investigations including the development of the new methods and technologies for preparation of SnSX and Cu2SnZnS4 thin films;
- performed the development of the cheapest and technologically advanced methods for deposition of thin films of semiconductor compounds on the substrate;
- improving front and back contacts in view of long-term stability, conductivity, transparency (TCO), as well as the related deposition methods;
- providing a wide range of optical, electrical and structural analysis techniques to characterize and the cells in the implementation of the Project;
- developing a technology for depositing the protective coatings to the single solar cells (or solar module);
- establishing of quantitative relationships between process parameters and the parameters of the materials on the one hand, and the characteristics of solar cells, on the other side;
- fabricating high performance SnSX and Cu2SnZnS4 - type solar cells up to 5 x 5 cm² device area, successfully tested in accelerated lifetime tests;
- presentation of the results to the international scientific community.
Role of Foreign Collaborators/Partners. Groups of scientists, led by Prof. Neelkanth G.Dhere (Program Director, Florida Solar Energy Center, University of Central Florida). Prof. I.M.Dharmadasa, Dept. of Engineering & Mathematics Faulty of Arts, Computing, Engineering & Sciences Sheffield Hallam University, United Kingdom expressed their wish to become Collaborators of this Project. These groups have a long tradition in the development and characterization of structural, electrical and optical properties of new semiconductor materials and solar cells. Will be carried out:(i) Exchange of information, discussion of results, joint publications.(ii) Review of quarterly and annual reports on the project all partners.(iii) Scientific visits of researchers to the U.S. and UK for discuss the results, the joint participation in the conferences.
Technical approach and methodology. The main innovation of the Project work is use of SnSX and Cu2SnZnS4 as alternative absorber materials for thin film solar cells and solar modules. The constituent elements of these compounds are safe for both environment and human health and abundant in nature.
Define the concepts for creating new designs of thin film solar cells and carrying out the experimental investigations, including the development of new methods and technologies of electrodeposition and sputtering for the production of laboratory samples of SnSx and Cu2SnZnS4 solar cells on flexible, nanostructured metal substrates and superstrates. The final goal of this task is to define the technique and, accordingly, process conditions to fabricate high-performance solar cells, with the criteria of band-gap optimization, surface planarization, composition, and physical characteristics of the films.
Carrying out theoretical investigations including both computer modeling of physical processes of solar energy transformation and thermal-physic processes in the multi - layer thin film solar cells based on SnSX and Cu2SnZnS4 as well as the optimization its physical parameters including the characteristics of single components of the solar cells. The modeling will be performed using AMPS-1D and 2D software to determine the optimum design elements of solar cells – layers thicknesses, criteria of choosing buffer layer and transparent conductive oxide, etc. The optimal structure for the SnSX and Cu2SnZnS4 cells will be proposed.
Selection of materials and synthesis technology of n-type buffer layer, the investigation of its physical characteristics - is the most difficult task. Therefore, will be selected semiconductor materials with wide band gap, with a lattice constant close to SnSX and Cu2SnZnS4 based on the results of modeling and experiments. It is planned to investigate ZnO:Al, ITO, TiO2, SnO etc as a transparent conductive layer.
Fabrication SnSX and Cu2SnZnS4 single solar cells and modules (up to 5 x 5 cm² device area) and testing to determine the critical conditions for the processes which could lead to optical and electrical losses affecting performance or stability. First solar cells will be prepared on glass substrates, and than will be fabricated and investigated on flexible solar cells, nanostructure metal substrates and superstrates. The results of investigations will be confirmed on the Collaborators' equipment.