The development of PV started since late 1950s where the first practical devices were demonstrated. Its true potential was revealed with the transistor revolution and advances in manufacturing and was leaded as the ultimate energy source. During the early times, as a means of terrestrial power, solar PV was used only for small electronic gadgets like calculators and watches. Research on optimizing solar cells efficiency was still undergoing in the 1980s and over the next decade, the PV industry witnessed a steady growth between 15% and 20%. Solar energy is one of the most important energy sources on which several global energy generation forms depend. Fossil fuel is basically million-years ago stored solar energy, biomass is stored chemical energy from the sun which is converted to fuel, wind energy is generated by air currents that are solar heated, and hydropower indirectly depends on the water cycle for its generation .
 K. Mertens, Photovoltaics Fundamentals, Technology and Practice, 2nd Edition, Wiley, Germany, 2014, pp. 15-16.