Monday, March 31, 2014: The PV cells are manufactured by hundreds of manufacturers worldwide and there are several different technologies available. There are three main types of commercially available PV cells:
• Mono crystalline silicon PV
• Polycrystalline silicon PV
• Thin film amorphous silicon PV
At present the first two categories dominate world markets constituting 93% of it the last one account for 4.2% of the market. There are other types of solar cells but is less in use which includes concentrated photovoltaic, hybrid solar cells, multi junction solar cells etc.
The silicon based technologies, crystalline Silicon, multi-crystalline Silicon, amorphous silicon are the dominant technologies at 24%, 19% and 12% efficiencies respectively at cell levels. The efficiencies at module levels are 5-6 % lower due to variety of reasons. Most of the Indian companies are producing at 15-17% efficiencies at cell levels and at about 12-13% at module levels. There is scope of improvement in different technologies.
A Thin-Film Solar Cell (TFSC), also called a Thin-Film Photovoltaic Cell (TFPV), is a solar cell that is made by depositing one or more thin layers (thin film) of photovoltaic material on a substrate. The thickness range of such a layer is wide and varies from a few nanometers to tens of micrometers. Many different photovoltaic materials are deposited with various deposition methods on a variety of substrates. Thin Film Solar Cells are usually categorized according to the photovoltaic material used.
The following categories exist:
• Cadmium Telluride (CdTe)
• Copper indium gallium selenide (CIS or CIGS)
• Dye-sensitized solar cell (DSC)
• Organic solar cell
• Amorphous silicon (a-Si)
On an average the efficiency of thin film cells are 6-12% furthermore the thin-film PV market is showing a spectacular annual growth rate of 126% in 2007. These thin film solar cells will be suitable for window and facades in Building Integrated PV (BIPV) technologies.
High efficiency solar cells with concentrators: Highest efficiency solar cells have micro morph triple junction Ge/GaAs/GaInAsP materials. Technology is quite intricate and cost of triple junction solar is quite high. Hence, these cells are primarily used for satellite applications. For terrestrial applications, these cells are used in high concentration mode to reduce usage of costlier cells. Using optical reflectors, light is concentrated from 200-500 times
on 1 cm2 active area. The Sun is tracked daylong in two dimensions to keep the sunspot on device area. Only few companies have mastered the cell and tracker technologies. There is need to know better and perfect the cell and tracker technologies [12].
