太阳能电池转换效率

Research on New Technologies of Photoelectric Conversion Efficiency in Solar CellTianze LI, Chuan JIANG, Cuixia SHENG School of Electric and Electronic Engineering Shandong University of TechnologyZibo 255049 ,Chinae-mail: ltzwang@Hengwei LU,Luan HOU, Xia ZHANG School of Electric and Electronic Engineering Shandong University of TechnologyZibo 255049 ,Chinae-mail: henrylu007@Abstract—The characteristics of the solar energy and three conversion mode of solar energy including photovoltaic conversion, solar thermal conversion, and photochemical conversion are represented in this paper. On this basis,the materials used in solar cell, as well as the working principle of solar cells, the factors of low convert efficiency of solar cells and the two major bottlenecks encountered in the solar application are analyzed.The idea that spontaneous arrangement of compound organic molecules is achieved by changing the molecular arrangement structure of the organic thin-film solar is put forward. The new structure of liquid crystal layer come into being accordingly so that the electron donor and the receptor molecules of the mixture are separated, and the contacting area between them is enlarged. So the efficiency solar photovoltaic is improved. The research and development of this new technology can solve the technical problem of the low conversion efficiency of solar cell, and open up an effective way to improve the conversion efficiency of solar cells. At last,the prospect of solar photovoltaic technology, solar energy exploit technology and the development of industry is offered in the article.Keywords- photoelectric conversion efficiency; electron donor and recipient; photovoltaic generate power technologyI.I NTRODUCTIONEnergy is the material basis of human society survival and development. In the past 200 yearsˈthe energy system based on coal, oil, natural gas and other fossil fuel has greatly promoted the development of human society. However,material life and spiritual life is increasing, the awareness of serious consequences brought from the large-scale use of fossil fuels is increasing at the same time: depletion of resources, deteriorating environment, in addition to all of the above, it induce political and economic disputes of a number of nations and regions, and even conflict and war. After in-depth reflection of the development process of the past, human advance seriously the future path of sustainable development. Today in the 21st century, there is no a problem as important as a sustainable energy supply, especially for the benefit of solar energy development and has been highly concerned by all mankind. Around the world are faced with limited fossil fuel resources and higher environmental challenges, it is particularly important to adhere to energy conservation, improve energy efficiency, optimize energy structure, rely on scientific and technological progress, development and utilization of new and renewable sources.After analyzing two bottleneck problems which affect the conversion efficiency of the solar cell, we put forward a new structure of molecular arrangement of the solar cell to improve the conversion efficiency of the solar cell.II.T HE F EATURES O F S OLAR A ND T HREE C ONVERSIONM ODESA.The Features of SolarSolar resources are solar radiation energy on the entire surface of the earth. Solar energy has four features. Firstly, solar energy is sufficient. The gross of solar radiation energy on the surface of the earth is about 6h1017kWh every year. It can be used several billions of years, which is reproducible and cleanest. It isn’t monopolized by any groups or coutries. Secondly, the energy density of solar energy is low. People want to obtain higher energy density by condensers. Thirdly, because of climatic change, the solar energy is mutative. For example, cloudy day and rainy day, the solar energy is weak. People should consider energy storage or use auxiliary devices which provide conventional energy to use solar energy in a row. Forthly, because of the earth rotation, the earth revolution and the angle between the axis of rotation and the orbital plane, days and sensons must change on the earth, solar energy must change too. Fifthly, use of solar energy can make energy level appropriate allocation, so heat energy is made used of. When the sun light shines on the earth, part of the light is reflected or scattered, some light is absorbed, only about 70% of the light which are direct light and scattered light passes through the atmosphere to reach the surface of the earth. Part of the light on the surface of the earth is absorbed by the objects surface, another part is reflected into the atmosphere. Fig.1 shows the schematic diagram of the sun incident on the ground.Figure1. Schematic diagram of the sun incident on the ground978-1-4244-7739-5/10/$26.00 ©2010 IEEEB.Three Conversion ModesThe use of solar energy technologies are divided into the following three ways on the energy conversion methods, such as photoelectric conversion, light-heat conversion, photochemical convertion. The light-heat conversion among them is the most widely used, which is a TECHNOLOGY that can change solar radiant energy into heat energy.III.T HE P RINCIPLE A ND M ATERIAL O F T HE S OLAR C ELLA.The Principle of The Solar CellThe principle of Solar cell is based on the semiconductor photovoltaic volt effect. Solar radiation is direct converted to electrical energy. When p-type silicon and n-type silicon connect, the interface will be formed between p-type and n-type the silicon in the crystal, that is, a pn junction. The basic structure is a large-area plane pn junction. As a result of electron and hole diffusion near the junction area, form the built-in electric field pointing form n to p area in the junction area. If the light on the solar cell is absorbed in the interface, the photon with enough energy can inspire electron from the covalent bond in the p-type silicon and n-type silicon and then produce electronic - hole pair.The more electron in the interface,the greater electric current. Light energy absorbed by the interfacial layer is stronger and interface layer that is, the greater the battery area, and the current formed in the solar cellis also greater.Fig.2 shows schematic diagram of crystalline silicon solar cellFigure2. Schematic diagram of crystalline silicon solar cellB.Analysls of MaterialIn principle, all semiconductor materials have photovoltaic effect, which can be used for solar cells. So in theory, all of the semiconductor materials should be solar photovoltaic materials, photoelectric material has all physical appearance of semiconductor materials. There are three reasons. Firstly, limitof physical appearance of semiconductor materials makes theoretical conversion efficiency of solar cells produced by some materials low, which don’t have development and application value. Secondly, the purification and the preparation of materials are difficult, all semiconductor materials don’t satisfy the high purity which should be needed by produced solar cells in the present technical conditions. Thirdly, the cost of materials and producing solar cells limits development, if the cost is very high, it is of no concern to devlop and apply. Though there are many kinds of semiconductor materials, real practical application in solar cell industry of semiconductor materials must be rare.As materials of solar panels, there are a lot of soalr cells produced by silicon so far. Silicon is a semiconductor material. Controllable doping of boron or phosphorus is to change the conductivity of pure silicon. The outer shell of phosphorus has 5 electrons, combination with silicon crystal bonding only need 4 electrons. The fifth electron is close to freedom, which can transfer and form current in the crystal. The number of impurity in the crystal essentially determines the number of current carriers and electroconductibility of doped silicon by changing doping content for purpose. Doping phosphorus or other 5 valence atom called n-type silicon.Silicon can be doped by boron, the outer shell of which has 3 electrons. The boron atom is short of a electron and combines with the adjacent electron of silicon in the silicon crystal lattice. The vacancy location is called “ hole ”. The doped silicon by similar boron is called p-type silicon. PN junction exists joint between n-type silicon and p-type silicon, which is core of semiconductor and solar cell. According to solar spectrum filling the demand of photoelectric conversion, by theoretical analysis, the band gaps of semiconductor materials which are made solar cells are 1-2eV, and when the band gap is about 1.4eV, the transformation efficiency is highest. The semiconductor materials are divided into direct bandgap and indirect bandgap. The photoabsorption coefficient of semiconductor material of direct bandgap is high, and the photoabsorption coefficient of semiconductor material of indirect bandgap is low. Gallium arsenideof micron thickness of direct bandgap absorbs all soalr light, but above 100­m silicon may comapare with.From 2003, there are two provision sources of international solar cell materials, such as semiconductor industries and specilized production.The solar cell materials of semiconductor industris are 50t/a. The semiconductor industry in China from grade material about 50t/a. Because of China semiconductor industry electronic level (EG) polysilicon production ability, ability of small ChanChang 100t/a, total 200t/a, insufficient reach high cost, scale, EG polycrystalline silicons are mostly imports, therefore, is not directly to provide DengWaiPin PV industry or scraps of polysilicon. China special grade silicon solar photovoltaic material research and production is almost blankIV.I NFLUENCE F ACTORS O F S OLAR B ATTERY C ONVERSIONE FFICIENCY A ND I MPROVING M EASURESA.Influence Factors of Solar Battery Conversion EfficiencyIn recent years,there are many problems in the application of solar energy technologies, especially the conversion efficiency of the battery technology has encountered many obstacles: the shading effects of grating on the surface of solar cell; the loss of surface reflection; the loss of optical transmission;the loss of internal composite; the loss of surfacecomposite. To solve these problems, the following newtechnologies are developed: PTP/OTP antireflection coating;laser carving groove buried grating technology; rongmian technology; back contact electrode which is to overcome the problem of surface grating shading;efficient back reflect technology; light absorption technology. With the application of these new technologies, issusing a series of studies which is focus on solar cell materials, conversion efficiency and stability ,inventing many new types of cell, which is greatly enhancing the conversion efficiency of solar cells.B.The Two Big Bottlenecks of Soalr Energy ApplicationThe core of solar energy appliction is generating electricity, generating electricity system is like a mini power station, which absorbs solar light, and directly changes solar into electrical energy. Not only satisfying their own electricity demand, excess electricity can also be incorporated into the power grid. The key bottleneck of limited solar energy application is technical environment and policy environment. Interconnection model with solar power equipment based on urban and rural power grid, far higher power grid companies may not buying grid type household solar power equipment redundant power. Even if the government subsidies, still quite difficult. To solve the key technical problems, is to reduce the cost of electricity can, in the true sense of the large-scale promotion.C.Solutions of Improving The Photovoltaic Efficiency ofSolar Cell and MeasuresTo improve solar cell conversion efficiency, reduce costs are the key to the development of photovoltaic technology.1˅Solutions of improving the photovoltaic efficiency of solar cellAt present the impact of major obstacle to large-scale application of photovoltaic cells is its high manufacturing costs. In many power generation technologies, solar photovoltaic is still one of the highest cost, therefore, the main objective to the development of solar power generation technology is to design new battery structure by improving the existing manufacturing processes, to develop new battery materials,so the manufacturing cost is lower and improve the efficiency of photoelectric conversion., there are two main factors to improve the efficiency of photovoltaic solar cells: First is how to make electron donor and receptor molecules in the mixture in the separate state; the second is how to expand the contact area between the two. In order to meet these two conditions, After studying the simulated new materials of molecular structure of the biofilm, hydrophobic side-chain and hydrophilic side-chain can be added,then to combine the two types of material to study the arrangement of the molecular structure, in order to form a liquid crystal state layered structure to improve the photoelectric conversion efficiency.2˅Measures of improving the photovoltaic efficiency of solar cellFirstly, according to the practical situation, policies and regulations which encourage use of renewable energy sources should be made.Secondly, encouraging industrial development, active exploring the market. In order to cause the solar energy to become one of following energy in the mid-21st century, must expand the investment, through the industrial production technology attack, the digestion absorption and so on, causes the light to bend down the manufacture industry technically to surpass the international standard, through the drive policy, encourages the Major industry to participate in the solar energy recovering technology positively the industry activity. Through encourages the policy to promote to expend, the development remote border district light bends down the market.Thirdly,China should be combined with "in western development strategy. Solar energy should be as a key construction project.The government should make implementing measures and programs of all use of solar energyin the western regions. Solar energy should be as the region's subsequent alternative sources.Forthly, Increasing introjection of basic research, such as new thin film solar cells, solar energy based materials, selective absorption films of solar spectral and other spectral reflection, the functional membrane, which greatly reduce the cost of using solar energy.V.S OLAR ENERGY T ECHNOLOGY A ND P ROSPECTWith the energy shortage growing and environmental pressures increasing, the depletion of oil is almost like a curse bringing disturbance to mankind. States have begun to develop renewable energy, in which development and utilization of solar energy has become the most hot "new favorite" of renewable energy. Development of solar energy has been the the general trend, and it is not far from solar energy era. The average annual growth rate of World PV modules was about 15% in the past 15 years. In the late 90s, the development is more rapid, and the average annual growth rate was more than 30% in the recent 3 years. The PV module production reached 200MW in 1999.In the industry, states has been to reduce cost by expanding the size ,improving the degree of automation, advancing the technical level, and opening up the market, and tremendous progress has been made. Efficiency of the Commercialization cell is from 10% ~13% to 13% ~ 15%, and the production scale develop from 1 ~ 5 MW/a to 5 ~ 25 MW/a and is expanding to 50MW even 100MW. PV component production cost down to below three dollars/W. India has the leading position in developing countries. There are currently more than 50 companies are involved in manufacturing about PV technology, including 6 solar cell manufacturing plants and 12 factories of components production, with 11MW annual production of components and about 40MW cumulative installed capacity. Promote the useof solar energy is of benefit to the people. Promotion and useof solar energy products in the the whole society, can directly reduce energy consumption, save money, reduce pollution and beautify their homes. Each unit, business, family and individual is the beneficiary of great significance.A.Applications in SpaceThe first application field of photovoltaic technology is in space as a human satellite power, and later prevalence to the ground application.Solar cell can work in a wide range of sun intensity and temperature for a long period of time, with high reliability, high efficiency, long life and good anti-radiation properties, etc. making it obtain a wide range of application as a ideal space power. So far the vast majority of all types of aircraft launched into outer space by humanity are using solar cells as power supply.B.Solar LightThe solar light is a solar-powered light, which is composed of solar components, batteries, charge-discharge controller, lighting circuits and poles, etc. Light, electricity, machinery, control technologies etc.that the light is gather in integral whole, and often integrate with the surrounding scenic environment. As long as sunny is enough it can install in situ, the light is a green environmentally friendly product and free from the effects of power lines,without ditching and embedding, non- consumption of conventional energy,and attracted a wide spread attention and applicationC.Solar CarWith the arrival of the 21st century, the automotive industry advanced countries are researching and developing in energy saving and environment-friendly electric car. Solar-powered electric car developed rapidly in some developed countries as a result of advances in technology, especially the improvement of the cell and control technology. The primary users of solar-powered electric car are urban and rural middle-income residents, individual traders, and the tourism sector.D. The Application of PV in The Communications and The HighwayThe most familiar application of Solar photovoltaic power system is communications in the industrial field. Solar power used in unmanned microwave relay station, cable maintenance station, electricity / radio / communications / paging power systems, rural telephone carrier photovoltaic systems, small communication equipment, and soldier GPS-powered, etc.Because of their unique characteristics of the highway, it is one of the solar photovoltaics place. Power supply system of highway plays a crucial role in the safety of the highway. In the urban areas of less electricity, if you use mains as power supply, the cost of pull-based power grid is very expensive. If using solar energy photovoltaic power generation on the highway to supply power to necessary electrical facilities, it is energy saving, environmental protection and economic security. Its applications is in the following areas: First, the service area on the highway which is away from the city power can build photovoltaic power station or photovoltaic-diesel hybrid systems,to supply area lighting, catering and other power needs to the service; The second is the emergency telephone system. the highway pass through many remote areas, in order to deal with emergency incidents, an emergency call must be provided as a means of ing the solar-powered long-distance transmission distribution equipment is not necessary, there is no transmission loss, safe and reliable when operate.R EFERENCES[1]Xing Yunmin,Tao Yonghong. Modern energy and technology of powergeneration. Xian: Press of Xidian University, 2007[2]Prince M B. Silicon solar energy converters.J Appl Phys,26:534-540(1955)[3]Kallmann H,Pope M.Photovoltaic effect in organic crystals.J ChemPhys,30:585-586(1959)[4]Wu Zhijian, Ye Zhiquan, Shen Hui.The utilization of New energy andrenewable energy. Beijing: Press of Mechanical Industry, 2006[5]Zhao Yuwen, Wu Dacheng, Li Xudong, Song Shuang. Development ofChina's Photovoltaic industry and market. Solar (SOLAR ENERGY),(3):7-10(2007)[6]Chapin D M,Fuller C S,Pearson G L. A new Silicon p-n junctionphotocell for converting solar radiation into electrical power.J Applphys,25:676-677(1954)[7]Li Jianbao, Li jingFeng. The new energy material and applicationtechnology. Beijing: Tsinghua university press, 2005[8]Wang Gehua. Energy and sustainable development. Beijing: Chemicaltechnology press, 2005[9]Yang Deren. Solar battery materials. Beijing: Chemical technologypress, 2007[10]Tang Huixiang, Yan Mi, Zhang Hui. Study of CuInS2 produced bychemical bath deposition. The 21st century new solar technology.Shanghai: Shanghai jiaotong university press,2003。