Solar

Polycrystalline - suited for residential and commercial applications both on-grid and remote. Poly-Si cells are less expensive to produce than single crystal silicon cells, and so the price by Wc is more efficient.

Simple explanation - Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon.
Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction. The complementary positive charges that are also created (like bubbles) are called holes and flow in the direction opposite of the electrons in a silicon solar panel. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.

Polycrystalline silicon - made from cast square ingots - large blocks of molten silicon carefully cooled and solidified. Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient.

The procedure of extracting pure poly-crystalline silicon from tri-chlorine-silan can be (among others) performed in special furnaces developed by Siemens.The furnace walls are additionally cooled preventing formation of any unwanted reactions due to gas side products. The procedure results in pure poly-crystalline silicon used as a raw material for solar cell production.

Poly-crystalline silicon can be extracted from silicon by heating it up to 1500°C and then cooling it down to 1412°C, which is just above solidification of the material.The ingot (block of silicon), sawn with diamond saw into thin silicon wafers, is a foundation for solar cell production. Wafers of 1 mm in thickness sawn with 1/10 mm precision are placed between two plan-parallel metal plates, which rotate into opposite directions. The procedure enables wafer thickness adjustment to 1/1000 mm precisely.

The improved multicrystalline cell performance results from enshrouding cell surfaces in thermally grown oxide to reduce their detrimental electronic activity and from isotropic etching to form an hexagonally symmetric "honeycomb" surface texture. This texture reduces reflection loss as well as substantially increasing the cell's effective optical thickness by causing light to be trapped within the cell by total internal reflection. ©1998 American Institute of Physics.