Advantages of Amorphous Silicon
Silicon can exist in several different forms. The most common form found in semiconductor devices is crystalline silicon, c-Si. While c-Si has relatively high electrical conductivity, its material properties limit its use for broader applications. There is another form of silicon, amorphous silicon, a-Si. a-Si has several distinct advantages:
- It may be deposited at lower temperatures, < 400 °C, which allows a wide variety of substrates to be used for growth, including some plastics for printed electronics.
- a-Si is much less susceptible to mechanical degradation and pulverization which is especially important in lithium ion battery applications.
- Another advantage a-Si has with regard to lithium ion battery applications is a higher potential of lithiation (reaction with lithium) which reduces the amount of lithium dendrites (lithium crystals formed on electrode surfaces). Suppression of dendrites improves battery safety and improves cycle life.
- a-Si has a lower manufacturing cost.
- With regard to photovoltaic applications a-Si has better blue light absorption and superior thermal properties which leads to a lower cost of produced electricity.
Right now widespread adoption of a-Si as a material is limited by the commercial availability of a suitable silicon precursor. One such precursor that would allow low temperature a-Si growth using a variety of synthetic and fabrication techniques is cyclohexasilane (CHS). CHS not only produces a-Si at the lowest temperature of any known polysilane, but does so with growth rates that are much higher.