Solar cells: semiconductor devices, Physics

A solar cell or photo voltaic cell is a semiconductor device that converts photons from the sun into electricity. It can also be defined as a semiconductor electrical junction apparatus which absorbs and changes the radiant energy of sunlight directly and efficient into electrical energy. In general solar cell that includes both solar- non solar sources of light is termed as photo voltaic cell. The change of sunlight into electrical energy in a solar cell includes three major processes: - absorption of the sunlight in the semiconductor, generation and separation of free positive and negative charge to different regions of the solar cell creating a voltage in the solar cell and transfer of these separated charges through electrical terminal to the outside application in the form of electric current.

APPLICATIONS: - solar cells are prepared from single crystal silicon. Historically solar cell have been used in situations where electrical power electrical power from the grid is unavailable, such as in remote area power system, earth orbiting satellites, consumer systems, hand hold calculators or wrist watches, remote ratio telephones and water pumping. Recently, solar cells are particularly used in assemblies of solar molecules (photo voltaic arrays) connected to the electricity grid through an inverter often in combination with a net metering arrangement. Solar cell is regarded as one of the key technologies towards a sustainable energy supply.

 THREE GENERARION DEVELOPMENT OF SOLAR CELL:-

FIRST: - The first generation photo voltaic consists of a large area, single layer p-n junction diode, which is capable of generating useable electrical energy from light sources with the wavelengths of solar light. The cells are typically made using silicon wafer. First generation photo voltaic cells also known as silicon wafer based solar cells are the domain technology in the commercial production of solar cells accounting for more than 85% of the solar cell market.

SECOND: - the second generations of photo voltaic materials is based on the use of thin film deposits of semiconductors. These cells are typically designed with high efficiency, multiple junction photo voltaic cells. Afterwards the benefit of using a thin film of material was noted, reducing the mass of material required for cell design. This contributed to a forecast of highly reduced costs for thin film solar cells. However, most of the assembly costs for depositing thin film solar cells are still significantly higher than for the bulk silicon technologies.

THIRD: - The third generation photo voltaic are very difficult from the order two, broadly defined as semiconductor devices which do not relay on a traditional P-N junction to separate photo generated charge carriers. These new devices include polymer solar cells, photo electrochemical cells, and mono crystal cells. To understand the electronic behaviour of a solar cell, it is useful to create a model which is electrically equivalent and is based on the discrete electrical components whose behaviour is well known. An ideal solar cell can be replicated by a current source in parallel with a diode. In practices no solar cell is ideal, so a shunt resistance and a series resistance component model added to the model.

 

Posted Date: 7/9/2012 1:30:18 AM | Location : United States







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