The solar cell production process can be broken down into the following stages.
Solar cell production process
Metallurgical Silicon to Polysilicon
Silicon is the second most abundant element in the earth’s crust (after oxygen),
and is commonly found as sand, which is in the form of silicon dioxide.
Polysilicon
Metallurgical silicon is produced by removing oxygen in a carbon-arc reduction furnace.
This is then purified through a complex chemical process involving chlorination
and distillation. The distilled gas is fed into a deposition furnace where it is
decomposed into solar grade polysilicon. 90% of the world's solar cells are made
of silicon.
Polysilicon to Ingots
The polysilicon is placed into a crucible, which is put into a furnace. There it
is heated to melting point, reaching temperatures of 1500ºC.
Multicrystalline ingot
The molten liquid is then crystallised into a solid state through the process of
cooling from the base up, in which the few remaining impurities rise to the top.
This results in a multicrystalline ingot of extremely pure silicon weighing up to
275 kg.
Ingots to Wafers
The ingots/rods are cut into smaller bricks by high-precision wire saws, which are
in turn cut into very thin slices, known as 'wafers'. The thickness of the wafer
varies, but can be as low as one fifth of a millimetre.
Silcon wafer
There are about 50 wafer producers globally, of which the top five have almost 50
percent of the market. PV Crystalox Solar is the largest pure play producer of multicrystalline
wafers in the world.
Wafers to Cells
An alkaline solution is used to smooth away any damage the wire saws may have caused
to the wafers, followed by the etching of the outer face to give the surface a texture
to increase the level of sunlight absorbed. Next a dopant element is added to in
low concentrations in order to alter the optical/electrical properties of the semiconductor,
followed by a thin layer of anti-reflecting material to maximise light absorption.
The last step is to add electrical contacts, usually through screen-printing.
Cells to Modules
Solar cells are the heart of solar modules. The cells are connected into strings
that are then encapsulated in polymers under glass. Modules can produce up to 500
watts and manage up to 1000 volts.
Solar module
Modules to Systems
Modules are the sections of a solar system. A system can be just one module, or
thousands. Systems are tailored to meet specific needs, with variations such as
battery storage to provide AC or DC power, inverters, connectors and power controls.
Large solar system
