Types of PV cells.
With the production of monocrystal silicium cells a bar is made out of one large crystal (a monocrystal). This bar is cut into thin slices. This way of production makes an higher output per cell available because of the purity of the crystal all the way to the edge. The essential efficiency of a complete PV panel is hardly influenced. Mono crystal silicon was origionally only use for the production of microchips.
The production of polycrystal cells is a lot cheaper Liquid silicon is poured into bars and cut into cells. During the curing proces of the silicon different crystal structures of various shapes appear. Because of defects on the edges, efficency of these types of cell is lower. Polycrytal bars however can be cut into square cells, this gives in a fabricated panel a better use of the total surface. The efficicency loss is eliminated compared to monocrystal panels.
When a photovoltaic layer is sprayed onto glass or a different substrate material we speak of thin-film cells. A layer thinkness of less than 1 µm is achieved (To compare: the thickness of a human hair is 50-100 µm.) Because of this lower material use and costs thin film cells are a lot cheaper than conventional PV cells, but so is the efficency. Thin film cells are mainly used in smaller applications like watches and pocket calculators. Some panels that can be used as building supplies like siding have been developed. The future of these cells is unclear, if efficency is resolved, a big step could be made by the these cells.
One more ?
There is one more type commonly know as ‘cell’ but it usually is a complete solar-panel that exists out of multiple poly-cells and is covered in epoxy. Due to the average small size it’s not called a panel.