It has to be mentioned here that PV is eventually not only c-Si versus TF. Best PV efficiencies have been achieved by far with III–V cells. Since 2001 these cells have been improving at an
impressive average of one percentage point per year. After achieving an efficiency of 44.4% with a 3-junction cell, the attention has shifted recently to the 4-junction cell which hits the current PV cell efficiency record of 46%. Due to cost factors III–V cells can only be used in high concentration PV systems. These include high concentration optics and accurate solar tracking [25]. They are appropriate for geographic areas with high direct solar radiation. High
concentration PV has still a very modest market share, although the long-term perspectives are promising. There is also a big number of other emerging PV technologies including Organic and
Dye-sensitized cells, as well as Quantum Dot and Perovskite cells. Depending on the specific technology, some basic aspects such as efficiency, life expectancy, costs and large-scale manufacturability have still to be improved before considering the technology mature for commercialization.