Amorphous Silicon Vs Crystalline Silicon
The main difference between amorphous silicon vs crystalline silicon is the physical structure of each substance. Amorphous silicon (a-Si) is a non-crystalline, or amorphous, form of silicon while crystalline silicon (c-Si) is a crystalline form of the same element. Both substances are used to create solar cells, although c-Si is far more commonly employed due to its higher efficiency.
At an atomic level, the differences between a-Si and c-Si are stark. A-Si has a disordered arrangement of atoms that lack any long range order—it does not have a repeating unit cell like c-Si—while c-Si consists of regularly spaced atoms arranged in an ordered lattice structure. As a result, a-Si has fewer defects within it than its crystalline counterpart; these defects can impede electron movement within the material and reduce solar cell efficiency.
At an application level, the two forms of silicon differ in terms of their electronic properties. A-Si has lower optical bandgap energy than c-Si, meaning that it can absorb more photons from sunlight and convert them into electricity at lower light intensities than its crystalline form. This makes a-Si particularly useful for thin film solar cells which require less energy to fabricate and have high performance at low light intensities such as indoors or overcast days.
Due to its disordered structure however, electrons move through a-Si slower than they do through c-Si, so its power conversion efficiency is lower—5–6% compared to 15–20% for mono/polycrystalline cells respectively—though this gap has come down significantly in recent years with advancements in technology. Furthermore, due to the absence of grain boundaries in a-Si which hinder electron movement, carriers experience fewer barriers when moving from one atom site to another resulting in faster charge transport rates compared to c-Si materials; because of this, thin film devices can be fabricated with very low dark current densities which allows them to operate at higher temperatures without degrading as quickly as their crystalline counterparts would under similar conditions.
In conclusion then, while both forms of silicon possess distinct advantages over one another depending on what type of device they’re used for and how much energy is required to fabricate them (as well as their respective power conversion efficiencies), their main difference lies within their atomic structures; specifically that a-si lacks any long range order compar