Correlation of structural and optoelectronic properties of thin film silicon prepared at the transition from microcrystalline to amorphous growth

Photovoltaic properties of 4 µm thick microcrystalline silicon p–i–n solar cells have been studied, over a range of crystallinity determined using Raman spectroscopy. Low-crystallinity material (below 10%) appears to absorb disproportionately strongly in the infrared, possibly due to increased light scattering or to relaxation of the crystal momentum selection rule. A minimum in solar cell efficiency is observed under AM1.5 illumination when V_OC ≈ 580 mV, with blue response most strongly affected. This is consistent with a reduction in electron mobility to a value below that of amorphous silicon for low-crystallinity material, in agreement with time-of-flight measurements.