(1)give me all the information about solar cell & dopping in english or gujarati.
(2)suggest me the e-book about solar cell & dopping in english or gujarati.
(3)which materials is used in dopping recently?

solar cell details in gujarati language

Most solar cells which are used today are based on crystalline silicon. The silicon can be mono-crystalline or poly-crystalline. Monocrystalline material is produced by the Czrochalski-process, while polycrystalline material is usually prepared by molding. In both cases the generated material is cut to wafers by wire saws. The wafers serve then as substrate material for the solar cell.

The solar cells consists mainly of silicon and is called therefore thick film solar cell, in contrary to thin film solar cells where the semiconductor layers are deposited on substrate of a different material. The bulk silicon is usually lightly p-doped, and conductive for positive charge carriers or holes. On the front side a thin heavily n-doped layer has to be formed by doping, which is conductive for negative charge carriers or electrodes. This way a p/n-junction is formed, which can separate the charge carrier pairs, generated by the absorption of sunlight. On the front side and on the back side metallic contacts have to be formed in order to drain the solar current. At the backside a holohedral aluminium layer is deposited, while at the front side silver contact fingers are generated, which allow most of the sunlight to pass into the cell. Finally a silicon nitride antireflection coating ARC is attached to the front side in order to increase absorption of the sunlight. The last production step is the assembly of the solar cells to solar modules.

Diffusion furnaces for doping crystalline silicon solar cells.
The doping of the upper, heavily n-doped layer is done with phosphorous as doping material. Two main procedures are used:
Doping from the gas phase by using phosphorousoxychloride POCl3.
Doping with doping paste attached by screen printing.
Tube furnaces for doping solar cells with phosphorousoxychloride.

Horizontal furnaces or diffusion furnaces from Koyo Thermo Systems ensure cost effective doping with high throughput. The LGO heating elements, used in this furnace have a very low thermal mass and can reduce therefore the process time. They can also save energy and costs for the doping process. All normal sizes of solar wafers can be processed in this type of furnace. Liquid POCl3 is supplied in a bubbler. Nitrogen passes at a well defined temperature through the liquid and is transporting the dopant. Typical doping temperature is 800 - 900°C.

The latest development of Koyo allows now also the continous doping of silicon wafers with POCl3 in a tube furnace. The wafers are carried through the tube on quartz cars with a load of 100 wafers each. The design of the cars is critical in order to obtain a good temperature uniformity and the process results of the POCl3 doping is therefore also affected seriously. Gas curtains at both ends of the tube separate the process room from the environment.

Two tubes installed beside each other allow simple automation.
The footprint gets lower because there is no need for a conventional loading station.
Throughput is increase much, because there is no time loss for loading or unloading wafers.
The furnace is saving energy, because there are no heating and cooling cycles.
There are also no thermic losses by the move out of a transportation conveyor band, because such a band is not installed.
The gas consumption is lower, because no purge cycles are necessary.
By the more simple configuration of the system, price is also reduced.
vertical furnace For higher demands to the homogeneity of the doping profile or to the automation level, vertical furnaces are available. The smallest version of a Koyo Thermo Systems vertical furnace can be very well used especially for the use in research and development of solar cells. The furnace model VF1000 is designed as a mini-batch furnace, has a manual loading and is therefore very flexible regarding sample sizes. This vertical furnace is equipped with a cost saving LGO heating element. The process performance equals the big production versions of vertical furnaces for IC production. The price of this unit is similar to the price of a horizontal tube in a horizontal furnace.

For mass production, Koyo Thermo Systems developed a special vertical furnace, which gives better process results compared to a horizontal one, but still does not increase much the production costs for solar cells. This twin furnace loads 3-4 boats in one vertical tube and has therefore a capacity of 600-800 solar cells. This is the same capacity that you get on a horizontal furnace. Automation is easier to do on a vertical furnace.

Conveyor furnaces for doping of solar cells using doping paste.

Doping with doping paste works with rather harmless materials and allows the usage of a simple conveyor furnace, which is well suited for mass production and can be intergrated easily in in-line production systems. The dopand is diffusing in the furnace from the doping paste into the silicon material. Temperature and anneal time determine the thickness of the generated n-doped top layer. The Koyo conveyor furnace model 47-MT with mesh belt transportation system can be used for this application.

conveyer furnace

For research and development, Koyo can offer a small type conveyor furnace model 810, which is constructed similar to the large furnaces and can simulate a production environment.

Dopant:
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance (in very low concentrations) to alter the electrical or optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that were in the crystal lattice of the base material. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities.