Up to this point, all that we have focused on is monocrystalline silicon; that is, silicon made from a single large crystal, with all the crystal planes and lattice aligned. There's one thing we haven't yet mentioned about monocrystalline silicon: it has what is called an indirect band gap. This means that, in order for light to be. Semiconductors can be made from alloys that contain equal numbers of atoms from groups III and V of the periodic table, and these are called III-V semiconductors. Group III elements. Monocrystalline silicon and the III-V semiconductor solar cells both have very stringent demands on material quality. To further reduce the cost per watt of energy, researchers sought materials. Solar cells that involve liquid dyesare actually quite similar to batteries. There are electrodes at either end, and a substance that is losing an electron while another is gain an electron (oxidation and reduction, also known as redox). The only difference in a solar cell is that the electron loss (into the conduction band) starts with absorption. A Russian mineralogist named Lev A. Perovski discovered a class of materials that were, some time later in 2009, discovered to be useful in solar cells. Originally they were studied for ferroelectricity and superconductivity. These materials bear his name and are known as perovskites. They follow the general formula ABX3, where A and B are both.
