Single Crystalline Silicon
Single crystalline silicon is usually grown as a large cylindrical ingot producing circular or semi-square solar cells. The semi-square cell started out circular but has had the edges cut off so that a number of cells can be more efficiently packed into a rectangular module. In single crystalline silicon material the crystal orientation is defined by Miller indices.
A particular crystal plane is noted using parenthesis such as Similarly, the crystal directions are defined using square brackets, e. To denote the crystal directions, single crystal wafers often have flats to denote the orientation of the wafer and the doping. The most common standard is the SEMI standard:. Skip to main content.http://gatsbyland.co.uk/todo-acerca-de-las-casas-wonder-readers-spanish.php
WO2009140406A2 - Crystal growth apparatus for solar cell manufacturing - Google Patents
Width is controlled by precise control of temperature, speeds of rotation, and the speed the seed holder is withdrawn. The crystal ingots from which wafers are sliced can be up to 2 metres in length, weighing several hundred kilograms.
Larger wafers allow improvements in manufacturing efficiency, as more chips can be fabricated on each wafer, with lower relative loss, so there has been a steady drive to increase silicon wafer sizes. The process begins when the chamber is heated to approximately degrees Celsius, melting the silicon. When the silicon is fully melted, a small seed crystal mounted on the end of a rotating shaft is slowly lowered until it just dips below the surface of the molten silicon.
The shaft rotates counterclockwise and the crucible rotates clockwise [ citation needed ]. The boule can be from one to two metres, depending on the amount of silicon in the crucible.
Mono silicon crystal growth
The electrical characteristics of the silicon are controlled by adding material like phosphorus or boron to the silicon before it is melted. The added material is called dopant and the process is called doping. This method is also used with semiconductor materials other than silicon, such as gallium arsenide. When silicon is grown by the Czochralski method, the melt is contained in a silica quartz crucible. Oxygen impurities can have beneficial or detrimental effects.
Carefully chosen annealing conditions can give rise to the formation of oxygen precipitates. These have the effect of trapping unwanted transition metal impurities in a process known as gettering , improving the purity of surrounding silicon.
However, formation of oxygen precipitates at unintended locations can also destroy electrical structures. Additionally, oxygen impurities can improve the mechanical strength of silicon wafers by immobilising any dislocations which may be introduced during device processing.
However, oxygen impurities can react with boron in an illuminated environment, such as that experienced by solar cells. This results in the formation of an electrically active boron—oxygen complex that detracts from cell performance. The impurity concentration in the solid crystal that results from freezing an amount of volume can be obtained from consideration of the segregation coefficient. From Wikipedia, the free encyclopedia. Method of crystal growth.
Silicon bulk growth for solar cells: Science and technology - IOPscience
Handbook of Crystal Growth: Fundamentals Second ed. Amsterdam, the Netherlands: Elsevier B.
- Czochralski process?
- Solidification of Silicon for Solar Cells.
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Retrieved on December 30, Retrieved Bibcode : ITNS