“…Although Solar Energy only occupies a small proportion in current renewable and sustainable energy, its development was rapid in recent years [3][4][5], photovoltaic (PV) technology can convert the sunlight into DC (direct current) electricity directly, solar cells could be used in off-grid and grid electric power systems, the size and number of solar cells and modules could be chosen according to the electric power demand of the systems easily, thus PV technology was used more conveniently than other kinds of renewable and sustainable energy [6]. The scale of worldwide PV industry is becoming larger and larger [7,8], the worldwide total production of solar cells and modules had reached 38.5 GW in 2012, the worldwide total cumulative amount of PV power plants had reached nearly 100 GW in 2012 [9], the total production of solar cell modules was about 24 GW in China in 2013 and the total amount of PV power plants was about 7.9 GW in China in 2012 [10], it was estimated that the worldwide electricity generated by solar cells will reach 280 TW h in 2030 [4,11]. There are many kinds of solar cells, and about 90% of the worldwide solar cells are crystalline silicon solar cells, which are made of monocrystalline and multicrystalline silicon wafers [3], others include III-V, thin film, dyesensitized, organic solar cells, and so on [6].…”