交大开元太阳能

The production of solar cells based on semiconductor materials based on its operating principle is to use materials absorb solar energy photovoltaic photovoltaic after conversion in response, according to the different materials used, solar cells can be divided into:

1, silicon solar cells;

2, with inorganic salt such as III-V compounds gallium arsenide, cadmium sulfide, copper indium selenium compounds, such as multi-material for the battery;

3, functional polymer materials prepared by the sun can be battery;

4, nano-crystalline solar cells, and so on.

Regardless of the materials to make batteries, solar cells in general requests are Material:

  1, the band gap semiconductor materials can not be too wide;

  2, to have a higher photoelectric conversion efficiency;

  3, the material itself does not cause pollution to the environment;

  4, to facilitate the industrial production of materials and material properties of stability.

Based on the above aspects, is the ideal silicon solar cell material, which is silicon solar cells to the main factors. However, with the continuous development of new materials and related technology to other material-based solar cells also show that more and more attractive prospects. In this paper, a brief overview of the solar cell and the type of research, and discussed the development of solar cells and trends.

1 Department of silicon solar cells

1.1 single crystal silicon solar cells
Series silicon solar cells, silicon cells can convert Dayang the most efficient, most mature technology. High-performance single crystal silicon cell is built on high-quality single crystal silicon and related materials into the thermal processing technology based on. Now the power to single crystal silicon technology has matured in recent in battery production, is generally used on the surface texture, firing passive zone, area, such as doping technology, the development of batteries are flat silicon cells and groove Monocrystalline silicon gate electrode buried in the battery. To improve the efficiency of conversion depends mainly on the surface of silicon micro-structure to deal with doping and zoning process. In this respect, Germany Fu Langhuo fee falaj Fort Solar System Research Institute maintains a leading position in the world. The technique photo-lithography technology to cell surface texture, made of inverted pyramid structure. And on the surface of a 13nm. Thickness of the oxide layer passivation and two-reflection coating by the combination. By improving the process of electroplating the gate to increase the ratio of width and height: more than a battery system conversion efficiency over 23%, the largest value of up to 23.3 percent. Kyocera Corporation prepared a large area (225cm2) single-crystal solar cell power conversion efficiency of 19.44 percent for domestic Beijing Solar Energy Research Institute is also active high-performance crystalline silicon solar cell research and development, the development of high-performance single crystal silicon flat battery (2cm X 2cm) reached 19.79 percent conversion efficiency, the groove gate electrode buried in crystalline silicon cells (5cm X 5cm) up 8.6 percent conversion efficiency.

Monocrystalline silicon solar cell conversion efficiency is the highest in the large-scale application and industrial production is still dominant, but because of the single crystal silicon material prices and the cumbersome process of the batteries affected, resulting in high cost single crystal silicon At least, to a significant reduction in the cost is very difficult. In order to save high-quality materials, single crystal silicon cells to find alternative products, the development of the thin film solar cells, polysilicon thin film solar cells and thin film amorphous silicon solar cells is a typical representative.

1.2 polysilicon thin film solar cells
The normally crystal silicon solar cells in the thickness of 350 ~ 450μm made of high-quality silicon, silicon from this dip or casting silicon ingots from the Juge. Therefore, the actual consumption of silicon material more. In order to save materials, from the mid-70 began in the low-cost polysilicon thin film deposited on the substrate, but because of the growth of silicon film grain size, not made of valuable solar cells. In order to obtain large-size grain of the film, people have never stopped, and a lot of ways. At present, preparation of polycrystalline silicon thin film batteries use chemical vapor deposition, including the low-pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) process. In addition, the liquid phase epitaxy (LPPE) and the sputtering deposition could be made available for preparation of polycrystalline silicon thin film batteries.

Chemical vapor deposition is the main SiH2Cl2, SiHCl3, Sicl4 or SiH4, as the reaction gas, a certain degree of protection in an atmosphere of silicon atoms to form and deposited on the substrate heating, the choice of substrate materials in general Si, SiO2, Si3N4, and so on. But the study found that in non-silicon substrates is difficult to form a larger grain, and easily form a gap between grain. To solve this problem is first in LPCVD substrate Shen Chi-thin layer of amorphous silicon layer, and then this layer of amorphous silicon layer annealing, the greater the grain, and then in this layer on the seed Thick polysilicon thin film deposition, recrystallization technology is a very important aspect of the current technology are solid-phase crystallization of the law and the Central re-melt crystallization. In addition to the polysilicon thin film batteries using the re-crystallization process, also used almost all of the preparation of single crystal silicon solar cell technology, such a system, the conversion efficiency of solar cells has increased remarkably. Germany falaj Fort Hall area using solar energy research institute recrystallization technology in the FZ Si substrate on a silicon-cell conversion efficiency of 19%, Japan's Mitsubishi with the preparation of the battery, the effective rate was 16.42 percent.

Liquid phase epitaxy (LPE) is a principle of law by molten silicon in its mother's body, the lower the temperature of precipitation silicon membrane. Astropower U.S. companies LPE Preparation of the battery efficiency of 12.2%. China photovoltaic technology development center Chen Zheliang LPE method used in the metallurgical grade silicon on a silicon crystal growth, and a design similar to the crystalline silicon thin film solar cells a new type of solar cells, known as the "silicon tablets of" solar energy Battery, but the performance has not yet seen the report.

As the polysilicon thin film batteries used in the silicon single crystal silicon than the less efficient and no recession, and there may be low-cost substrate material on the preparation, the cost much lower than the single crystal silicon cells, and more efficient than amorphous Silicon thin film battery, polysilicon thin film solar cells will soon be in power to dominate the market.

1.3 amorphous silicon thin film solar cells
The development of solar cells on two key issues: the conversion to increase efficiency and reduce costs. As the amorphous silicon thin film solar cells, low cost, ease of large-scale production, generally people's attention and rapid development, in fact, as early as in the early 1970s, Carlson, and so began the development of amorphous silicon cells, during the past few In its development has been rapid development of the world's been many companies in the production of this type of battery products.

Although the material as amorphous silicon solar battery is a good material, but because of its optical band gap is 1.7eV, making their own materials on the long-wave solar radiation spectrum of the region is not sensitive, so restrictions on the amorphous silicon solar cells The conversion efficiency. In addition, the efficiency of the photoelectric light as an extension of time and decay, the so-called photo-induced recession of the S-W effect, making the battery performance of instability. To address these issues in this track is prepared laminated solar cells, solar cells are stacked in the preparation of p, i, n single-junction solar cell layer and then deposited on one or more sub-Pin of a battery system. Tandem solar cells increase the conversion efficiency of single-junction cells to address instability that the key question:

  ① it to a different band gap of Materials group with Taiwan, in response to the increased scope of the spectrum;

  ② top of the battery-i-thin, light generated by the electric field strength has been no big change to ensure that i layer of photo-induced carriers out;

  ③ generated at the end of the battery carrier is about one-half of the battery, reducing the effect of photo-induced recession;

  ④ tandem solar cell battery is the son of the series with.

Amorphous silicon thin film solar cells have a lot of preparation, response, including sputtering, PECVD method, LPCVD law, the response of raw materials for gas H2 diluted SiH4, and the glass substrate for the main piece of stainless steel, made of amorphous silicon Thin film battery technology through a different process can be a single-node tandem solar cells and batteries. At present, amorphous silicon solar cells made major progress in the study: First, the laminated structure of the three amorphous silicon solar cell conversion efficiency of 13%, setting a new record; in the second. Laminated three annual production capacity of solar cells up to 5MW. United Solar Energy Company (VSSC) obtained the highest single-junction solar cell conversion efficiency of 9.3 percent for the third band gap three cell stack to the highest conversion efficiency of 13%.

  Above the highest conversion efficiency in a small area (0.25cm2) to get the battery. Had reported single-node amorphous silicon solar cell conversion efficiency of more than 12.5%, Academia Sinica, Japan adopted a series of new measures, a system of amorphous silicon cells for the conversion efficiency of 13.2 percent. With regard to domestic battery in particular, amorphous silicon thin film tandem solar cell research, Xinhua Geng's Nankai University, and other industrial materials used to back Al electrode prepared for the area 20X20cm2, to 8.28 percent conversion efficiency of a - Si / a-Si tandem solar cells.

As the amorphous silicon solar cells with high conversion efficiency and low cost and light weight, and other features, has a great potential. At the same time, but because of its stability is not high, a direct impact on its practical application. If you can solve problems and improve the stability of the conversion rate, then the sun can be amorphous silicon cell is the main development of solar products.

More than 2 yuan compound film solar cells

In order to find an alternative to silicon cells, in addition to the development of polycrystalline silicon, amorphous silicon thin film solar cells, and other materials continue to develop solar cells. This consists mainly of gallium arsenide group III-V compounds, cadmium sulfide, cadmium sulfide copper and selenium stop film batteries. These batteries, although the cadmium sulfide, cadmium telluride polycrystalline thin film battery efficiency than that of amorphous silicon thin film solar cell efficiency, lower costs than single crystal silicon cells, as well as easy-to large-scale production, but because of a highly toxic cadmium, Causing serious environmental pollution, crystalline silicon solar cells is not the best alternative III-V compounds of gallium arsenide and copper indium selenium thin film batteries due to the higher conversion efficiency by widespread attention. GaAs belonging to the group III-V compound semiconductor materials, its energy gap is 1.4eV, just for the high rate of absorption of sunlight value, it is an ideal battery material. GaAs, and other III-V compounds cell membrane preparation MOVPE and the main use of LPE technology, which MOVPE prepared GaAs substrate by the thin film battery dislocation, the reaction pressure, III-V ratio, the total flow and other parameters.

In addition to GaAs, other III-V compounds such as Gasb, GaInP, and other battery materials have been developed. Germany in 1998 falaj Fort solar system, a system of the Institute of GaAs solar cells for the conversion efficiency of 24.2 percent, recorded in Europe. Preparation for the first time the battery GaInP for 14.7 percent conversion efficiency. Table 2. In addition, the Institute also uses a stacked structure of the preparation of GaAs, Gasb batteries, the batteries will be two separate batteries stacked together, GaAs as the battery, under the battery is used Gasb, obtained by the efficiency of the battery to reach 31.1% .

Copper indium selenium CuInSe2 referred to as CIC. CIS materials can be reduced to 1. leV, suitable for solar photovoltaic conversion, and, CIS thin film solar photo-induced recession, there is no problem. Therefore, CIS as a high-conversion efficiency of thin film solar cell materials have attracted people's attention.

CIS thin film cells are prepared by the law and selenium vacuum deposition method. Vacuum evaporation method is the use of their steam evaporation source copper, indium and selenium, and selenium is the use of laminated film H2Se selenide, but the law difficult to get uniform composition of the CIS. CIS thin film battery from the 80's first 8% of the conversion efficiency to the development of the current 15%. Japan's Matsushita Electric Industrial Development Corporation of the gallium-doped CIS battery, the photoelectric conversion efficiency of 15.3% (area 1cm2). 1995 U.S. renewable energy research to develop a conversion efficiency of 17. l% of the CIS solar cells, which is so far the world's highest conversion efficiency of the battery. It is estimated that in 2000 the CIS cell conversion efficiency to reach 20%, the equivalent of polycrystalline silicon solar cells.

CIS solar cells as semiconductor materials, with a low price, good performance and simple process, will be the future development of solar cells is an important direction. The only problem is that the source material, indium and selenium are due to the relatively rare element, type of battery development will inevitably be limited.

 3 multi-layer polymer-modified electrode solar cell

In the solar cells in a polymer in place of inorganic materials is just the beginning of the solar system, a father of the research. The principle is to use different oxidation reduced polymer different redox potential in the conductive material (electrode) to carry out multi-storey complex on the surface, made of inorganic similar to the P-N junction of conducting a one-way device. One of the electrodes from the inner-reduction potential of lower polymer-modified, the outer layer of polymer-reduction potential of the higher direction of electron transfer can only be transferred from the inner to the outer layer; another modification of the electrode on the contrary, and The first two types of polymer electrode on the reduction potential is higher than the latter two types of polymer-reduction potential. When the two modified electrode into photosensitizing agent with the wave of electrolysis time. Photosensitizing agent after the absorption of electron transfer to the reduction potential of the lower electrode, the reduction potential accumulated in the lower electrode to the outer layer of polymer electronics can not be transferred only through external circuit through higher-reduction potential of the electrode Back to the electrolyte, therefore, outside the circuit in the light current generated.

As the organic material flexible, and easy to produce, the source of a wide range of materials, such as at the end of the cost advantages of large-scale use of solar energy in order to provide cheap power is of great significance. However, organic materials of the solar cell research is only the beginning, whether life or efficiency of the battery can not and inorganic materials especially compared to the silicon cells. Can be developed into practical products, yet to be explored further.

         4 chemical nanocrystalline solar cell

In the Department of silicon solar cells in solar cell development is the most mature, but because of high costs, is far from meeting the large-scale application. To this end, it has been in technology, new materials, thin film battery technology in such areas to explore, among which the development of new nano-crystalline TiO2 solar cells by the chemical energy of great importance to scientists at home and abroad.
Gratzel Switzerland since the successful development of nano-TiO2, a professor of chemical battery can Dayang, some units are also under way in this regard. Chemical nanocrystalline solar cells (the cells NPC) by a band gap semiconductor material modification, the assembly to another big gap on the formation of semiconductor materials, narrow band gap semiconductor materials using transition metals such as Ru, and Os of organic compounds Dye-sensitized, the bandgap semiconductor materials for nano-TiO2 and made of polycrystalline electrodes, in addition to the battery NPC also choose to restore a proper oxide electrolyte. Nano-crystalline TiO2 How it works: dye molecules absorb light energy Transition to the sun excited state, the excited state of instability, rapid e-injected into the immediate vicinity of TiO2 conduction band, the dye is lost e-soon receive compensation from the electrolyte into the conduction band TiO2 The electric conductive film to enter in the final, and then through the outer loop generate photocurrent.

Nano-crystalline TiO2 solar cells has the advantage of its cheap cost and simple process and the stability of performance. Photoelectric its efficiency and stability in more than 10%, making the cost of silicon solar cells is only 1 / 5 to 1 / 10. Life can reach more than 2O years. However, such battery research and development has just begun, it is estimated that in the near future will be gradually stepped onto the market.

 5 trends in the development of solar cells

From the above discussion, we can see that as the material of solar cells, III-V compounds and the CIS, and other communities by the preparation of the rare element, although they made a high conversion efficiency of solar cells, but the source material, this Types of solar cells in the future can not be dominant. And the other two types of nano-crystalline solar cell batteries and solar electric polymer modified electrode to the existing problems, they just started the study, technology is not very mature, conversion efficiency is still relatively low, these two types of batteries is still in the exploratory stage, a short period of time Should not be a substitute for the Department of solar cells. Therefore, the conversion efficiency of the source material and perspective, the focus of future development of silicon solar cells is still in particular, polysilicon and amorphous silicon thin film batteries. As the amorphous silicon and polycrystalline silicon thin film batteries have a higher conversion efficiency and relatively low cost, single crystal silicon will eventually replace the battery, the market leading products.

Improve the efficiency and reduce costs of solar cells is prepared to take into account two main factors for the Department of silicon solar cells, in order to further improve the conversion efficiency is more difficult. As a result, the focus of future research in addition to continuing to develop new battery materials should be focused on how to reduce costs onto the existing high-conversion efficiency of solar cells in high-quality, made of silicon, which is the most cost silicon solar cells Money. Therefore, how to ensure that the conversion efficiency is still higher to lower down the cost of the substrate is particularly important. Also in the future development of solar cells need to be addressed urgently. Recently, some foreign countries have adopted a system of silicon technology as a strip of polycrystalline silicon thin film solar cell substrate, so as to minimize costs.