Amorphous silicon photovoltaics: order from disorder

Amorphous silicon (a-Si) solar cell technology has matured to a stage where there is currently a production of 30 MW peak/year. The progress is due to the continuous advances made in new materials, cell designs, and large area deposition techniques for mass production. The absence of long-range order, which is present in crystalline materials, has profound consequences on the properties of a-Si as a photovoltaic material, which exhibits both similarities as well as striking differences from crystalline silicon. It has also offered not only characteristics which make it excellent for thin film solar cells but also provides great flexibility in the design of different solar cell structures and in the manufacturing of large area monolithic modules. A review is presented of the nature and properties of a-Si based materials as well as an “ordered” evolution of solar cell structures which led to the continuous improvement in their performance and stability