How many types of compound photovoltaic cell are there? This chapter details the types and characteristics of compound photovoltaic cell.
There are four main types of compound photovoltaic cell, including copper indium selenium photovoltaic cell, gallium arsenide photovoltaic cell, cadmium telluride photovoltaic cell and polymer photovoltaic cell. Their definitions and characteristics will be described in detail below.
①Copper indium selenium photovoltaic cell.
It is a semiconductor film made by depositing copper, indium, and selenium ternary compound semiconductors on glass or other inexpensive substrates. Because the copper indium selenium battery has good light absorption performance, the film thickness is only about 1/100 of that of a single crystal silicon photovoltaic battery. The preparation of copper indium selenium thin film batteries generally adopts processes such as vacuum evaporation, selenization, and chemical vapor deposition. Among them, the vacuum evaporation method uses respective evaporation sources to evaporate copper, indium, and selenium; the selenization method first uses evaporation or sputtering to generate a copper/indium laminate film at a lower temperature of 200 to 300 ℃. Then the temperature is raised to 400-550°C, and heat treatment is performed in hydrogen selenide gas or selenium vapor to generate a copper indium selenium film. The copper indium selenium thin film battery has the characteristics of low material consumption, low cost, stable performance and no light-induced degradation. Its photoelectric conversion efficiency has grown from the initial 8% in the 1980s to the current 15%. It is estimated that the conversion efficiency of copper indium selenium thin-film batteries will reach 20% in recent years. Due to the advantages of the copper indium selenium thin film battery, especially the photoelectric conversion efficiency currently ranking first among various photovoltaic cell, it is called the cheap photovoltaic cell of the future internationally, attracting many institutions and experts to conduct research and development. However, copper, indium, and selenium are relatively rare elements, and the manufacturing of such batteries will encounter bottlenecks that restrict raw materials, which investors must fully consider.
② Gallium arsenide (GaAs) photovoltaic cell.
It is a III-V compound semiconductor photovoltaic cell. Compared with silicon photovoltaic cells, gallium arsenide photovoltaic cell have high photoelectric conversion efficiency. The theoretical efficiency of silicon photovoltaic cells is 23%, while the conversion efficiency of single junction gallium arsenide photovoltaic cell has reached 27%; it can be made into thin films and ultra-thin ones. The battery also absorbs 95% of sunlight. Gallium arsenide photovoltaic cell only need a thickness of 5-10um, while silicon photovoltaic cell need to be greater than 150um. The high temperature resistance performance is good. At 200°C, silicon photovoltaic cell can no longer work, while arsenic The efficiency of gallium arsenide photovoltaic cell is still about 10%; it can be made into more efficient multi-junction stacked photovoltaic cell. Theoretical calculations show that the ultimate efficiency of double-junction gallium arsenide cells is 30%, and that of triple-junction gallium arsenide cells The ultimate efficiency is 38%, and the ultimate efficiency of a four-junction gallium arsenide battery is 41%. At present, gallium arsenide photovoltaic cell are mostly prepared by liquid phase epitaxy or metal organic chemical vapor deposition technology, so the cost is high, the output is limited, and the price of gallium arsenide materials is expensive, which limits the arsenic to a large extent. The popularity and development of gallium photovoltaic cell. Gallium arsenide photovoltaic cell are currently mainly used in spacecraft and are the most ideal battery for space applications. Because of its high conversion efficiency and high temperature resistance, it is also particularly suitable for making a spotlight tracking power generation system, so that it has a new expansion in ground applications.
③Cadmium telluride photovoltaic cell.
Cadmium telluride is a compound semiconductor whose band gap is most suitable for photoelectric energy conversion. Photovoltaic cell made of this kind of semiconductor have a very high theoretical conversion efficiency. At present, the highest conversion efficiency actually achieved reaches 16.5%. Cadmium telluride photovoltaic cell are usually manufactured on a glass substrate. The first layer on the glass is a transparent electrode, and the following thin layers are cadmium sulfide, cadmium telluride and a back electrode. The back electrode can be a carbon paste or It is a thin layer of metal. There are many methods for the deposition of cadmium telluride, such as electrochemical deposition, near-space sublimation, short-distance vapor transport, physical vapor deposition, screen printing and spraying. The thickness of the cadmium telluride layer is usually 1.5~3um, and a thickness of 1.5um for cadmium telluride is sufficient for light absorption. The cadmium telluride photovoltaic cell has a simple structure, is easy to deposit into a large-area thin film, and the deposition rate is also high. Therefore, the manufacturing cost of cadmium telluride photovoltaic cell is low, and it is a new type of photovoltaic cell with good application prospects. It has become the main target of research and development in the United States, Germany, Japan, Italy and other countries. However, the pollution of the toxic element cadmium to the environment and the harm to the health of operators cannot be ignored. At present, experts are actively studying countermeasures and believe that they will be resolved in the near future, so that cadmium telluride photovoltaic cell will become one of the new energy sources for the future society.
④Polymer photovoltaic cell.
It uses the different redox potentials of different redox polymers to perform multi-layer composite on the surface of the conductive material to make a unidirectional conductive device similar to an inorganic PN junction. Common materials for polymer photovoltaic cell include polyethylene, polyacetylene, and poly-p-styrene. Really pure conjugate polymers are non-conductive. To make them exhibit semiconductor characteristics, the polymer must be ion implanted through processes such as physical doping to form P-type and N-type structures, respectively. Polymer solar cells generally have a sandwich structure, consisting of conductive glass (positive electrode), polymer photoactive layer and Al (negative electrode). When light irradiates the active layer from a certain side, a photovoltaic effect is generated to form an electric current. Compared with traditional semiconductor photovoltaic cell, which have complex structure, high cost, and large fluctuations in photovoltage affected by light intensity, polymer photovoltaic cell can be designed and synthesized by themselves due to their molecular structure, with large material selection, easy processing, good flexibility, low toxicity, and cost. Low characteristics, which is of great significance for large-scale use of solar energy and the provision of cheap electricity. Since the research on polymer preparation of photovoltaic cells has just begun, neither the service life nor the cell efficiency can be compared with inorganic materials, especially silicon cells. Whether it can be developed into a product of practical significance remains to be further studied and explored.
