EfficiencyThere are four kind of efficiency of a solar cell 1.reflectance efficiency 2.thermodynamic efficiency, 3.charge carrier separation efficiency 4.conductive efficiency. The overall efficiency is the product of each of these individual efficiencies.A solar cell usually has a voltage dependent efficiency curve, temperature coefficients, and shadow angles.Other efficiency are: thermodynamic efficiency,quantum efficiency,integrated quantum efficiency, Thefill factor mean the ratio of the actual maximum obtainablepowerto the product of the open circuit voltage and short circuit current.'' performance of a solar cell is determine from this , commercial solar cells have a fill factor greater 0.70. Grade B cells have a fill factor usually between 0.4 to 0.7.[15]Cells with a high fill factor have a lowequivalent series resistanceand a highequivalent shunt resistance, so less of the current produced by the cell is dissipated in the internal losses Illustration 1: Reported timeline of PV cellenergy conversion efficiencies (National Renewable Energy Laboratory united state

Material used for making solar cell solar cell is made from various material i.e. monocrystalline silicon,polycrystalline silicon,amorphous silicon,cadmium telluride, andcopper indium selenide,thin-filmslayers, organicdyes, and organicpolymers.,nanocrystalsand used asquantum dots(electron-confinednanoparticles). Manufacture solar cells are semiconductor devices,and Poly-crystalline silicon wafers are made by wire-sawing block-cast silicon ingots into very thin (180 to 350 micrometer) slices or wafers. The wafers are usually lightlyp-typedoped. To make a solar cell from the wafer, a surface diffusion ofn-typedopants is performed on the front side of the wafer. This forms a pn junction a few hundred nanometers below the surface.Anti-reflection coatings, to increase the amount of light coupled into the solar cell, are typically next applied. Silicon nitride has gradually replaced titanium dioxide as the anti-reflection coating, because of its excellent surface passivation qualities. It prevents carrier recombination at the surface of the solar cell. It is typically applied in a layer several hundred nanometers thick using plasma-enhanced chemical vapor deposition (PECVD). Some solar cells have textured front surfaces that, like anti-reflection coatings, serve to increase the amount of light coupled into the cell. Such surfaces can usually only be formed on single-crystal silicon, though in recent years methods of forming them on multicrystalline silicon have been developed.The wafer then has a full area metal contact made on the back surface, and a grid-like metal contact made up of fine "fingers" and larger "bus bars" are screen-printed onto the front surface using asilverpaste. The rear contact is also formed by screen-printing a metal paste, typically aluminium. Usually this contact covers the entire rear side of the cell, though in some cell designs it is printed in a grid pattern. The paste is then fired at several hundred degrees Celsius to form metal electrodes inohmic contactwith the silicon. Some companies use an additional electro-plating step to increase the cell efficiency. After the metal contacts are made, the solar cells are interconnected by flat wires or metal ribbons, and assembled intomodulesor "solar panels". Solar panels have a sheet oftempered glasson the front, and apolymerencapsulation on the back. Earlier calculater and electronic devices which operate on solar cells as show in the image -Lifespansolar panel manufacturers is over 90% of rated output for the first 10 years, and over 80% for the second 10 years.Panels are expected to function for a period of 30 to 35 years.

Now a days china is playing very important rule in the manufacturing of solar pannels , in 2010 china made a solar pannels of an output 13GV , due to this great acheivement china is now called the largest producer of solar module