Monocrystalline silicon, or mono-Si, PV cells
Mono-Si photovoltaic cells (or PVs) are the oldest form of PV cells. Mono-Si cells use the purest form of silicon. As a rule, the higher the purity of the silicon in the cells, the higher the cell’s efficiency. But the purest silicon comes at a cost. So, mono-Si PV cells are pricier but offer over 20% efficiency, which is higher than other types of solar cells. Efficiency is measured in generation as a percentage of cell capacity.
Mono-Si had a 35% share, or 13.6 GW (gigawatts), of total global installation in 2013, totalling 39 GW. SunPower (SPWR) and JA Solar (JASO) specialize in manufacturing high-efficiency PV solar (TAN). First Solar (FSLR) recently started manufacturing mono-Si PVs to use in space-constrained applications. Due to the thicker layer of semiconductor material, mono-Si PVs take less space than other types of PVs.
Polycrystalline silicon, or p-Si, PV cells
P-Si cells use lower-purity silicon, leading to lower efficiency of about 16–18%. Meanwhile, the p-Si cell manufacturing process is simpler and more cost-effective. Out of a globally installed 39 GW in 2013, p-Si accounted for 55%, or 21.4 GW. P-Si cells are also known as “multi-Si cells.” JA Solar, Trina Solar (TSL), and Yingli Green Energy (YGE) are the largest p-Si cell producers by capacity.
First Solar (FSLR) is the leader in thin-film PVs. Thin-film PV cells were developed to lower costs by using lower quantities of silicon. As the name suggests, thin-film cells are thinner because they use a thinner layer of silicon. Thin-film PVs have lower efficiency of around 12–14%. However, First Solar achieved a record 17% efficiency in March 2014. Hanergy and First Solar (FSLR) are the largest manufacturers of thin film PV cells in the world.