Amorphous silicon

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Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. Silicon is a four-fold coordinated atom that is normally tetrahedrally bonded to four neighboring silicon atoms. In crystalline silicon this tetrahedral structure is continued over a large range, forming a well-ordered lattice (crystal). In amorphous silicon this long range order is not present and the atoms form a continuous random network. Not all the atoms within amorphous silicion are four-fold coordinated. Due to the dissordered nature of the material some atoms have a dangling bond. These dangling bonds are defects in the continuous random network, which cause undesired (electrical) behaviour. The material can be passivated by hydrogen, which bonds to the dangling bonds and neutralises this defect. Hydrogen passivated amorphous silicon has a sufficiently low amount of defects to be used within devices. The hydrogen is unfortunately associated with light induced degradation of the material, the "Staebler-Wronski Effect".

[edit] See also

• Nanocrystalline silicon
• Polycrystalline silicon

[edit] External links

• Amorphous Silicon Devices group at the University of Waterloo, Ontario, Canada
• Theory and Simulation at Ohio University, Athens Ohio
• National (U.S.) Renewable Energy Laboratory Information on Amorphous Silicon
• How electronic inks will work
• Xsunx - A company which has developed a manufacturing technique for transparent solar cells