Solar cells or photovoltaic cells are electric system that can be used to generate power from solar energy. This conversion is done by photovoltaic effect. Mono crystalline silicon wafer is used to make this cell. Solar modules are made from a good arrange of these cells. They capture and store energy from the sunlight and generate a huge amount of electricity. However, the amount of electricity depends on the size of the solar module. The term ‘photovoltaic’ comes from a Greek word. The meaning of that Greek word is ‘light and voltaic’. This word has been used in English since 1849. A. E. Becquerel was the man who at first recognized the photovoltaic process. This process was explained by the greatest scientist, Albert Einstein. For this he got the Nobel Prize in 1921. In 1954, the modern solar cell was developed at Bell Laboratories. That time, very highly efficient solar photovoltaic cells were developed. Silicon p-n junctions were used to make the cells.
That time, they didn’t make large cells. Little cells were made for tiny toys and small equipments. After some days, large solar cells were made for huge uses. However, the development was not fast. That time, the main use of the solar cell was in space applications. This was a very advanced technology since that time. The scientists worked hard to make it applicable to other applications in day-to-day life. They invented updated models of these cells. They tried at their best to reduce the price of these cells. They spread the applications of these cells whole over the world. People became able to apply them in their daily life. Electricity crisis is a big problem in the modern world. So, the scientists are working hard to apply the solar energy to the field of electricity. We know that electricity is generated because of the flowing of electron. The cells use the photons of the sunlight to excite the electrons and to flow them very quickly in order to generate electricity.
Since the works of Berman, there were a lot of improvements of solar energy. The cost was reduced to an average of $1 to $2 per watt. This was very economical for the people. The pressure during the production of electricity in general process was reduced at a great rate. From that time, large solar panels started to be used in different factories, industries and other commercial sectors. It saves a lot of electricity bills every month. This is now also are being used to meet the need of electricity in our houses. We can install solar panels in our houses by ourselves. However, for this, we need to receive short training on the installation of these panels. There are many companies, which give special training in the processes of installation of solar photovoltaic panels.
Solar cells are usually connected electrically. They are encapsulated as the module. These modules usually have sheets of glasses, and these glasses are generally placed in the front side where sunlight falls. These glasses allow the light to pass through it and also protect the semiconductor wafers which are very soft and sensitive. They can be damaged by external pressure or rain or wind-flow. The cells are to be connected in series for much production of electricity.
Thus, voltage is produced. If we connect them in parallel, higher current will flow. However, there will be a lot of problems with parallel connection. These cells work in three steps. At first, the photons come from the sunlight, and they hit the panels. The semiconductors like silicon absorb them. Electric potential difference is created. Current starts to flow through the semi conducting material in order to cancel the potential difference. That time, the material captures the current flow. The electrons flow in single direction. Then the solar photovoltaic cells convert the energy into electricity. The produced current is D.C. The efficiency of these cells is quite high. The efficiency of these cells using sunlight is over 85%. They are very much economic and friendly to the nature. It has no bad effect on environment.
These cells have become very much popular all over the world. Electricity is one of the basic needs of modern life. We can’t pass a single day without electricity. However, production of electricity is not increasing with the increase of population. So, electricity and power crisis is a burning question in modern days. The amount of storage energy is reducing day by day. So, it has become a headache for the scientists. They are trying to discover some new sources of renewable energy. Solar energy is such a kind of energy. It is very much cost effective. Only cost is the installation cost. The cost of the panels is quite high. However, the maintenance cost is very low. No other fuel is needed for these panels. Only sunlight is enough for them.
Different kinds of materials are used to make the panels. The materials must have the characteristics matched with spectrum of light. Light absorbing materials can be used here. Some cells are designed to convert the wavelengths of the sun ray efficiently. Crystalline silicon is the most efficient material. Proto-crystalline silicon presents twisted bonds.
They have deep defects. The conduction and valence bands are de-formatted. Solar cells made from these materials are not very much effective. Cells made of bulky silicon are more efficient than these cells. Cells made of amorphous silicon are also very much productive for the conversion of the sun light to electricity. This type of silicon has a more band gap than crystalline silicon. Thermal processing techniques enhance the crystal and structural quality of silicon. They provide higher efficiencies of solar cells. This type of cells needs the lower amount of materials.
Solar cells are used in lots of cases. They can be used in calculator or as battery in different electrical devices. However, they are largely used in generating electricity. These cells are used all over the world. People use them in their houses. They install the panels on the roof of their houses or in their kitchen or in any open place next to the houses where sun light is available. Before installing photovoltaic panels, people need some guideline about the installation. The companies, from whom people buy the solar cells, give some instructions and training on the installation of them accurately. After getting the training, they can install them properly.
At first, we have to select a suitable place of installation where sun light is available. We have to check the place perfectly whether it can tolerate the weight of the panels. We can keep the panels on a rack made from solid steel. Then we will connect them in series with wires. However, we will remain conscious about short circuiting. Because, short circuiting can damage the whole system. We can connect a regulator with the system.
It is used in order to control the amount of flow of electricity. The number of solar panels and the size of them depend on the total need of electricity. So, before installation, we have to calculate the full need of electricity of our residence and industries. For industries, panels of large size are needed. These panels store the solar energy in the daytime and convert them into electricity. At night, when there is no sun light, it uses the stored energy for supplying the electricity. It also can store energy when it does not get full sun light.
Solar cells are also used in space exploration and satellite. In this case, highly efficient multi junction cells are used. At first, the cost of this multi junction cell was very high. However, with the development of the technology, they are now cheap and very much available. Different types of semi conducting materials are used to make the cells.
Among them, the cell made of GaAs is the best one. Now, triple junction solar photovoltaic cells are being used. It has reached to the efficiency of 43.5%. This technology is presently being used in Mars Exploration missions. This mission is at this moment in time a very important mission for the scientists. Tandem solar cells are based on monolithic.
They are connected in series. Now, their demand has been raised very quickly. The triple junction GaAs cells were being used as a power source of Nuna in 2003, 2005 and 2007. Nuna has won the Dutch World solar challenge for four times. DSSC is made of very low-cost materials. DSSC means Dye-sensitized solar cells. They do not need to increase equipment in order to manufacture. Another type of solar cells is organic type solar cells. It is also known as polymer type solar cells. Now it has become a novel technology. It promises price reduction and a very quick return on investment. These solar cells can be found from a solution.
It can be produced at a high scale. The polymer and organic solar cells can be formed from thin films, which are about only 100 nm. These devices are different from inorganic solar cells as they do not depend on the huge built-in electric field at PN junction. They do not deal with the separation of holes and electrons. These electrons and holes are created when the photons are absorbed. These photons come from the sun light. The active region of the organic photovoltaic cells consists of two materials.
One of the materials works as the donor and another material acts as an acceptor. At the time of the conversion of the photon into the electron-hole pair, especially in the donor material, the positive and negative charges remain bound in an excision form. When it diffuses to the acceptor-donor interface, the charges are separated. It has been invented that, proto crystalline silicon causes high open circuit voltage. Now, there are a lot of research teams and groups on this topic. They are trying at their best in order to develop this technology.
There are many manufacturing companies of these cells in China, Japan, Germany and United States. They are offering good solar cells to the world people. Among them, the Chinese companies are playing a vital role within the field of solar energy. Their productions are now better than any other companies around the world. China has produced about 13 GW in 2010, which is half of the whole production in this world.
So, now China is the largest solar-energy producer in this world. The companies of United States are also very good. They are also producing a lot of solar power, which is very much essential. They are developing a lot in this field.
The life span of a photovoltaic solar cell is enough long. If we can install a solar panel perfectly, it will store energy and will convert it into electricity for several decades. The manufacturers give the customers about 90% warranty for first 10 years and 80% for the next 10 years. It is expected that these panels will work correctly for 30 to 35 years. However, proper care is needed.
We must check the connection and the wiring system with some days’ gaps. It will help to protect the whole system from any kind of damages. A good place of installation is very important for the installation and maintenance of the panels. These cells need heavy sun light, and this is its fuel. These panels also need some extra protections from heavy rainfall, strong wind flow and any kind of electrical and mechanical damages.
These are not only detrimental to the panels; these are also damaging to us. If short circuit occurs within the system, it will damage the whole electrical system of our house or industry and also can cause firing and burning.
Modern world is based on power and energy. People are using a huge amount of energy every day. So, the amount of energy throughout the world is decreasing day by day. So, energy crisis is prevailing in this world. Solar energy can play a very important rule. It can be an alternative energy.