Growing terrestrialsolar cells. But the cost of

Growing energy demand and environmental consciousnesshave turned human interest in renewable source of energy thatcan be used as an alternative to the fossil fuel. Among thevarious sources of renewable energy, photovoltaic (PV) hasproved its potentiality as a long-term, inexhaustible,environmentally friendly and reliable energy technology. As aresult, the use of photovoltaic systems is increasing in all overthe world as a green source of electricity. On a global scale,approximately 15,000 MW of new PV installations have beenadded during 20 I 0, amounting the entire PV capacity toalmost 40,000 MW and the amount is increasing gradually 1.Due to the poor efficiency of Silicon solar cells it becomescostlier than other conventional energy. Crystalline Si solarcells have the highest efficiency among the existing terrestrialsolar cells. But the cost of these solar cells is quite high due tosubstantial material usage which results in high Cost/Wp ratio.Solar Photovoltaic concentrators can reduce the cost of978-1-4673-1154-0112/$3 l.00 ©2012 IEEEterrestrial solar cells by reducing this ratio. This can beachieved by increasing the light intensity on the solar cells andgenerating more power from the given area. It is found that asthe concentration ratio increases the area of the cell decreases.Cell area decreases by two times if the concentration ratioincreases by same quantity for same power output. This alsoleads to the material saving. Since photovoltaic industry isalready facing a shortage of Si wafers, concentrators cell canbe an attractive option for material saving 2.Concentrator cells suffer power loss due to increasedvoltage drop in emitter and front metal grid. Resistance offront metal grid results in voltage. These resistances tend toreduce the power output and degrade the efficiency of thecells. Series resistance losses contribute to around 20% of thetotal input power 2. But these losses increases tremendouslywhen solar cell is operated at high concentration level. Theefficiency of a solar cell is given as-VoelseFF17 = —p;;;- (1)Where Voe is open circuit voltage, Ise is short circuit current,Pin is the total power in the light incident on the cell and FF isthe fill factor which depends on the internal voltage drop.Expression for the FF is given byFF = (1 – ..!::!..) ( 1 – ..!::!..In (Voe) – ILRS) (2)Voe Voe Vt VoeFrom the Equation (2) it is observed that the FF depends onthe series resistance Rs of the cell. Under concentrated light,the product of load current IL and series resistance Rs (ILRS)increases and these results in decrease of FF which affects theefficiency at high concentration levels 3.Screen printed front contacts are normally used on solarcells. In the screen printed fingers and busbars of a solar cell,light is absorbed and causes charge carriers to flow along thefingers to the busbars. These busbars and fingers of the solarcell have some geometrical pattern design. Efficiency of thecell depends on bus bar and finger design of the cells.