Solar energy is the inexhaustible renewable energy. Also clean energy, do not produce any pollution. In the effective use of solar energy, Can use is the sun arises in photoelectric the fastest, most vigorous development of research field, is one of the most of the project.
Make solar battery is mainly based on semiconductor materials, its working principle is using photoelectric material absorb the light after conversion reaction, according to the photoelectric from different materials and solar cell can be divided into: 1, silicon solar battery, 2 and inorganic salt as gallium arsenide III – V compounds, cadmium sulphide, copper indium selenium, multiple compound material for the battery, 3 and the sun arises functional polymer battery can, 4 and nanocrystalline solar battery, etc.
A, silicon solar battery
1 silicon solar cells work principle and structure
Solar power is the main principle of the photoelectric effect, semiconductor semiconductor main structure is as follows:
In the figure, the positive and negative silicon atom says that in the next round of four electronic silicon atom.
When the silicon crystals of adding other impurities, such as boron, phosphorus, when adding boron, silicon crystals will exist in a hole, it can refer to form below:
In the figure, the positive and negative silicon atom says that in the next round of four electronic silicon atom. And yellow said adding of boron atom, because only three around boron atom electronic, so will produce the blue shown into the hole, this hole because no electronic and became very unstable, easy absorption and electronic form, and the lack of semiconductor (P).
Also, with phosphorus atoms, because the phosphorus, so there are five atom electronic it will have a very active, electronic form N (visitors) type semiconductor. Yellow is the nucleus, red phosphorus is redundant electronics. The diagram below.
N type semiconductor contains more cavities and P type semiconductor contains more electronic, so, when P type and N type semiconductor together, will be in contact DianShiCha form, this is PN junction.
When P type and N type semiconductor together, in two kinds of semiconductor boundary region will form a special thin layer), the interface of the P type side negatively charged MMH, N side. This is due to the P type semiconductor cavity, N type semiconductor more than free electrons, appeared concentration. The electronic will spread to N, P the cavitation zone P will spread to N area, once the diffusion is formed by a point P “N”, to prevent inside field spread. After the balance, formed a special form of thin layers, which is DianShiCha PN junction.
When the chips are light, PN junction, N type semiconductor cavity to P type, and moving toward the P type electronic n-type area movement, thus forming from n-type area to P type of current. Then DianShiCha formed in PN junction, which formed the power. (shown below),
Due to the semiconductor not good conductors of electricity and electronics in n and p – through after in the semiconductor, if the resistance is very big, the loss is very big. But if all painted in the upper metal, sunshine is not produced by current cannot use metal mesh, so usually covered p – n “(pictured), comb electrodes to increase the area of incident light.
Another very bright, silicon surface will be reflected off of sunlight, cannot be battery using. Therefore, the scientists give it painted with a layer of reflection coefficient of very small diaphragm (pictured), will reflect the loss to 5% even smaller. A battery can provide the current and voltage, after all, so people will be limited battery (usually many 36) parallel connection or use, form of solar photovoltaic plate.
2 the silicon solar cell production process
Usually the crystalline silicon solar cells in the thickness is 3.5-450 muon m high quality silicon wafer, and this made on from the ingot casting tiras or saw on.
The method of the actual amount of silicone material more. In order to save material, there were more than batteries by polysilicon film chemical vapor deposition, including chemical vapor deposition (low LPCVD) and plasma enhanced chemical vapor deposition (PECVD) technique process. In addition, the liquid phase epitaxy (LPPE) and sputtering method can also be used for preparation of polysilicon film batteries.
Chemical vapor deposition is mainly SiH2Cl2, SiHCl3, SiCl4 or SiH4, for certain gases under the protective atmosphere reacts silicon atom and deposition in the heat of the substrate is generally selected Si substrate materials, etc., Si3N4 and SiO2 But the study found that in the silicon substrate to form larger grain, and easy in grain formed between the gap. To solve this problem is to use LPCVD deposition in the substrate a thin layer of amorphous silicon, the layer of amorphous silicon layer of annealing, get bigger grain, and then again in the seeds deposited on the wafer polysilicon film thickness, therefore, recrystallization technology is an important part of the current technology, main solid-phase crystallization and central melting recrystallization method. Poly membrane batteries used in recrystallization processes, almost all other USES for preparation of monocrystalline silicon solar energy cell technology, so that the solar cell can obviously improve the efficiency of conversion.
3 and nanocrystalline chemical solar cells
In silicon solar cells in the development of solar battery is undoubtedly the most mature, but due to the high cost, cannot satisfy the requirement of large-scale promotion application. Therefore, people have been constantly in technology, the new material, the battery film etc are explored, and the recent development of nanometer TiO2 energy crystal solar cell and scientists.
To dye sensitization nanocrystal solar battery (for example, this DSSCs) battery including transparent conductive film coated glass of basement, dye sensitization semiconductor materials, such as electrolyte of electrode parts.
As shown, white, red balls ball TiO2 said that dye molecules. Dye molecules absorb solar energy transition to excited excited, unstable, electronic quickly into adjacent TiO2, dye with lost quickly from electrolyte of electronic is compensated, TiO2 into the electricity in the final with conductive film and then enter through the outer loop current generated.
Nano TiO2 crystal solar cell’s advantage is that it is cheap cost and simple technology and stable performance. The photoelectric efficiency in production cost, only 10% for silicon solar cell 1/5 ~ 10. Life can reach 20 years. But because of this research and development of the battery has just started, estimates that the future will be progressively market.
Anode: dye sensitization TiO2 film (film) semiconductor
The cathode: platinum coated conductive glass
Electrolytes I3: I – - /
Dye battery application model:
Four, dye sensitization TiO2 solar cells handmade
1 make tio2 membrane
(1) the titanium dioxide powder into mortar and binders grinding
(2) then glass rod slowly in the conductive glass on the coating
(3) tio2 membrane in alcohol under the lamp sintering 10 ~ 15 minutes, then cooling
2 for the use of natural dye tio2 colouring
As shown, fresh and frozen blackberries, ShanMei, pomegranate seed or black tea, plus a tablespoon of water and the titanium dioxide film extrusion, then put on coloring, about 5 minutes, until the membrane layer into purple, if both sides membrane layer of non-uniform, can put into soak 5 minutes, then wash with ethanol, and soft paper gently dry.
3. Make the positive electrode
The shaded by the dye for electronic outflow of TiO2 an anode (namely). The positive electrode can be conductive glass of conductive plane (coated with conductive SnO2 membrane layer), using a simple multimeter can judge the side of the glass is conductive, use finger can also make judgment, conductive face relatively coarse. As shown, the conductive surface marked ‘+’, then use a pencil in the conductive face evenly coated graphite.
4. Add electrolyte
Using the iodine ion of solar battery electrolyte solution as, it is mainly used for reduction and regeneration of dyes. As shown on the membrane surface in titanium, add one to two drops electrolyte.
5 assembly batteries
After the coloring of tio2 membrane facing up on the table, in the film for one to two drops it drops containing iodine ion of electrolyte and iodine, then take the positive electrode conductive tio2 membrane facing down at. The two pieces of glass, use two little stagger the battery clamps, two pieces of glass exposed wires connected to the part. So, you just made of solar cells.
6 batteries testing
Outside the sunlight, detection you can generate electricity solar cells.