Carrier drift-mobilities and solar cell models for amorphous and nanocrystalline silicon

Hole drift mobilities in hydrogenated amorphous silicon (a Si:H) and nanocrystalline silicon (nc Si:H) are in the range of 10 3 to 1 cm 2 /Vs at room temperature. These low drift mobilities establish corresponding hole mobility limits to the power generation and useful thicknesses of the solar cells. The properties of as deposited a Si:H nip solar cells are quite close to their hole mobility limit, but the corresponding limit has not been examined for nc Si:H solar cells. We explore the predictions for nc Si:H solar cells based on parameters and values estimated from hole drift mobility and related measurements. The indicate that the hole mobility limit for nc Si:H cells corresponds to an optimum intrinsic layer thicknes s of 2 3 2m, whereas the best nc Si:H solar cells (10% conversion efficiency) have thicknesses around 2 2m.