BULK TECHNOLOGIES: THE bulk technologies are often known as wafer-based manufacturing. In other words in each of these approaches self-supporting wafers between 180 to 240 micrometers thick are processed and then soldered jointly to create a solar cell module. By far the most prevalent bulk material for solar cells is crystalline silicon abbreviated as a group as also known as “solar grade silicon”. Bulk silicon is separated into multiple categories according to crystalline and crystal size in the resulting ingot, or ribbon or wafer.
MONOCRYSTALLINE SILICON: Generally made use of the Czochralski process. Single crystal wafer tends to be expensive. And due to cut from cylindrical ingots, they do not totally cover a square solar cell module without a substantial waste of refined silicon. Therefore most C-Si panels have exposed gaps at the corners of four cells. Singly crystalline wafers can be made into excellent high efficiency solar cells but they are generally considered to be too expensive for large scale mass production.
POLY-OR-MULTI CRYSTALLINE SILICON: poly crystalline silicon wafers are made by wire sawing block cast silicon ingot. Large blocks of molten silicon are carefully cooled and solidified and then taken out in thin (180 to 350 micrometer) slice or wafers .The wafers are use usually lightly p-type doped. To make a solar cell from the wafer, a surface diffusion of n type do pants is on front side of the wafer. This makes a p-n junction a few hundred nanometres beneath the surface. Antireflection coating , which increase the amount of light coupled into the solar cell, are typically applied, next. These cells are less expensive to produce than single crystal cell but are less efficient.
They are formed by drawing flat thin films from molten silicon and having a multi crystalline structure. These flat wires or metal ribbons are then assembled into modules or solar panels. Solar panel has a sheet of tempered glass on the front and a polymer encapsulation at the back. These cells have lower efficiencies than poly-Si, but save on production costs due to
a great reduction waste , as this approach does not require sawing from ingots.