Production of solar batteries: technology and equipment

Mankind is striving to switch to alternative sources of electrical supply, which will help preserve the cleanliness of the environment and reduce the cost of generating energy. The production of a solar battery is a modern industrial method. The power supply system includes receivers of sunlight, batteries, control devices, inverters and other devices designed for certain functions.

The solar battery is the main element from which the accumulation and transformation of the energy of the rays begins. In the modern world for the consumer when choosing a panel there are many pitfalls, since the industry offers a large number of products, united under one name.

Silicon Solar Cells

These products are popular with modern consumers. The basis of their manufacture is silicon. Its reserves in the bowels are widespread, extraction is relatively inexpensive. Silicon elements favorably differ in the level of performance from other batteries of sunlight.

Types of elements

The production of solar cells from silicon is of the following types:

• Single crystal;
• Polycrystalline;
• amorphous.

The above-mentioned forms of devices differ in how silicon atoms are arranged in the crystal. The main difference between the elements is a different indicator of the efficiency of conversion of light energy, which in the first two species is approximately at one level and exceeds the values for instruments made of amorphous silicon.

Today's industry offers several models of solar collectors of light. The difference is in the use of equipment for the production of solar cells. The technology of manufacturing and a variety of initial material play a role.

Single-crystal type

These elements consist of silicone cells, fastened together. By the method of the scientist Czochralski, absolutely pure silicon is produced, from which single crystals are made. The next process is to cut the frozen and solidified semi-finished product into plates with a thickness of 250 to 300 μm. Thin layers are saturated with a metal grid of electrodes. Despite the high cost of production, such elements are used quite widely due to the high conversion rate (17-22%).

Production of polycrystalline elements

The technology of producing solar batteries from polycrystals consists in the fact that the molten silicon mass is gradually cooled. Production does not require expensive equipment, therefore, the cost of silicon production is reduced. Polycrystalline solar storage devices have a lower coefficient of efficiency (11-18%), in contrast to monocrystalline ones. This is due to the fact that during cooling, the mass of silicon is saturated with the smallest granular bubbles, which leads to an additional refraction of the rays.

Elements of amorphous silicon

Products belong to a special type, since their belonging to the silicon type comes from the name of the material used, and the production of solar batteries is performed using the technology of film devices. The crystal in the manufacturing process gives way to silicon hydrogen or a silicone, the thin layer of which covers the substrate. Batteries have the lowest efficiency value, up to 6%. Elements, in spite of a significant drawback, have a number of undeniable advantages that give them the right to stand in line with the above types:

• The absorption of optics is two to ten times higher than that of single-crystal and polycrystalline storage rings;
• Has a minimum layer thickness of only 1 μm;
• Cloudy weather does not affect the work of converting light, unlike other species;
• Because of the high index of bending strength without problems, it is used in difficult places.

Three of the above types of solar converters are complemented by hybrid products from materials with dual properties. Such characteristics are achieved if micronutrients or nanoparticles are included in amorphous silicon. The obtained material is similar to polycrystalline silicon, but it differs favorably from it with new technical parameters.

Raw materials for production of film-type solar cells from CdTe

The choice of material is dictated by the need to reduce the cost of production and increase the technical characteristics of the work. The most commonly used light-absorbing cadmium telluride. In the 70s of the last century CdTe was considered the main contender for space use, in modern industry it found wide application in the energy of sunlight.

This material is classified as a cumulative poison, so the debate on its harmfulness does not subside. Researches of scientists have established that fact that the level of the harmful substance arriving in atmosphere, is admissible and does not harm ecology. The level of efficiency is only 11%, but the cost of electricity converted from such elements is lower by 20-30% than from devices of the silicon type.

Beam collectors made of selenium, copper and indium

Semiconductors in the device are copper, selenium and indium, sometimes it is possible to replace the latter with gallium. This is due to India's high demand for flat-type monitors. Therefore, this substitution option is chosen, since the materials have similar properties. But for the coefficient of efficiency, replacement plays an essential role, the production of a solar battery without gallium increases the efficiency of the device by 14%.

Polymer-based solar collectors

These elements are referred to as young technologies, since they recently appeared on the market. Semiconductors from organic absorb light to convert it into electrical energy. For production, fullerenes of the carbon group, polyphenylene, copper phthalocyanine, etc. are used. As a result, thin (100 nm) and flexible films are obtained, which give an efficiency factor of 5-7% in operation. The value is small, but the production of flexible solar cells has several positive points:

• For manufacturing large amounts of money are not expended;
• The possibility of installing flexible batteries in bends where elasticity is of prime importance;
• Comparative ease and availability of the installation;
• Flexible batteries do not have a harmful effect on the environment.

Chemical etching in the manufacturing process

The most expensive in a solar battery is a multicrystalline or single-crystal silicon wafer. To maximize the rational use of silicon cut psevdokvadratnye figures, the same form allows you to tightly lay the plate in the future module. After the cutting process, microscopic layers of the damaged surface remain on the surface, which are removed by etching and texturing to improve the reception of the incident rays.

The surface treated in this way is a chaotically located micro-pyramid, reflecting from the face of which, light enters the side surfaces of other projections. The procedure for loosening the texture reduces the reflectivity of the material by approximately 25%. In the process of etching, a series of acid and alkaline treatments is used, but it is impermissible to greatly reduce the thickness of the layer, since the plate does not withstand the following treatments.

Semiconductors in solar batteries

The technology of producing solar batteries suggests that the basic concept of solid electronics is the pn-junction. If one combines the electronic conductivity of the n-type and the hole conductivity of the p-type in one plate, then a pn junction occurs at the point of contact. The main physical property of this definition is the opportunity to serve as a barrier and to transmit electricity in one direction. It is this effect that allows us to establish a full-fledged work of solar cells.

As a result of carrying out phosphor diffusion, an n-type layer forms at the ends of the plate, which is based at the surface of the element at a depth of only 0.5 μm. The production of a solar battery provides for a shallow penetration of carriers of opposite signs that arise under the influence of light. Their way into the zone of influence of the pn-junction must be short, otherwise they can extinguish one another at a meeting, without generating any quantity of electricity.

Use of plasma chemical etching

In the design of the solar battery, there is a front surface with an installed grid for shooting the current and the back side is a solid contact. During the phenomenon of diffusion, an electrical fault arises between the two planes and is transmitted to the end.

To remove the short circuit, the equipment for solar cells is used, which allows to do this with the help of plasma chemical, chemical etching or mechanical, laser. The method of plasmachemical exposure is often used. Etching is performed simultaneously for a stack of silicon sheets stacked together. The outcome of the process depends on the duration of the treatment, the composition of the tool, the size of the squares of the material, the direction of the ion flow jets, and other factors.

Application of antireflection coating

By applying a texture on the surface of the element, the reflection is reduced to 11%. This means that a tenth of the rays simply reflect off the surface and do not participate in the formation of electricity. In order to reduce such losses, the front side of the element is coated with a deep penetration of light pulses that do not reflect them back. Scientists, taking into account the laws of optics, determine the composition and thickness of the layer, so the production and installation of solar cells with such coating reduce the reflection to 2%.

Contact metallization on the front side

The surface of the element is designed to absorb the greatest amount of radiation, it is this requirement that determines the dimensional and technical characteristics of the applied metal mesh. Choosing the design of the front side, engineers solve two opposite problems. Reduction of optical losses occurs at thinner lines and their location at a great distance from each other. The production of a solar battery with increased grid dimensions leads to the fact that some of the charges can not reach the contact and is lost.

Therefore, scientists standardized the value of the distance and line thickness for each metal. Too thin strips open space on the surface of the element to absorb rays, but do not conduct a strong current. Modern methods of applying metallization consist in screen printing. As a material, silver-containing paste is the most justified. Due to its application, the efficiency of the element rises by 15-17%.

Metallization on the back of the device

The application of metal to the back of the device takes place according to two schemes, each of which performs its own work. A continuous thin layer on the entire surface, except for individual holes, is sprayed with aluminum, and the holes are filled with a silver-containing paste playing a contact role. The continuous aluminum layer serves as a kind of mirror device on the back side for free charges, which can be lost in the tattered crystal lattice bonds. With such a coating, solar panels are used for 2% more power. Customer feedback says that such elements are more durable and do not depend so much on cloudy weather.

Manufacture of solar panels by own hands

Power sources from the sun are not everyone can order and install at home, as their cost today is quite large. Therefore, many masters and craftsmen master the production of solar panels at home.

You can buy sets of photocells for self-assembly on the Internet on various sites. Their cost depends on the number of plates and power used. For example, small-capacity sets, from 63 to 76 watts with 36 plates, cost 2350-2560 rubles. respectively. Here, also, work elements that have been rejected from production lines for some reason are acquired.

When choosing the type of photoelectric converter take into account the fact that polycrystalline elements are more resistant to overcast weather and work with it more efficient than monocrystalline ones, but have a shorter life. Monocrystals have a higher efficiency in sunny weather, and they last much longer.

To organize the production of solar cells at home, you need to calculate the total load of all devices that will be powered by the future converter and determine the power of the device. Hence the number of photocells, taking into account the angle of the panel. Some masters provide for the possibility of changing the position of the storage plane, depending on the height of the solstice, and in winter - on the thickness of the fallen snow.

Various materials are used to make the case. Most often put aluminum or stainless corners, use plywood, particle board, etc. The transparent part is made of organic or ordinary glass. On sale there are photocells with soldered conductors, these are preferable to buy, since the assembly task is simplified. Plates do not stack one on the other - the lower ones can give microcracks. Solder and flux are preliminarily applied. To solder elements is more convenient, placing them immediately on the working side. At the end, the end plates are welded to the bus bars (wider conductors), then a minus and a plus are output.

After the work done, the panel is tested and sealed. Foreign masters use compounds for this, but they are quite expensive for our craftsmen. Homemade converters are sealed with silicone, and the back side is coated with acrylic based varnish.

In conclusion, it should be said that the reviews of the masters who made solar panels with their own hands are always positive. Once having spent money on the manufacture and installation of the converter, the family very quickly pays for them and starts saving, using free energy.