Determination of the mobility gap of intrinsic μ c - Si : H in p - i - n solar cells

Microcrystalline silicon ( μ c - Si : H ) is a promising material for application in multijunction thin-film solar cells. A detailed analysis of the optoelectronic properties is impeded by its complex microstructural properties. In this work we will focus on determining the mobility gap of μ c - Si : H material. Commonly a value of 1.1 eV is found, similar to the bandgap of crystalline silicon. However, in other studies mobility gap values have been reported to be in the range of 1.48 - 1.59 eV , depending on crystalline volume fraction. Indeed, for the accurate modeling of μ c - Si : H solar cells, it is paramount that key parameters such as the mobility gap are accurately determined. A method is presented to determine the mobility gap of the intrinsic layer in a p - i - n device from the voltage-dependent dark current activation energy. We thus determined a value of 1.19 eV for the mobility gap of the intrinsic layer of an μ c - Si : H p - i - n device. We analyze the obtained results in detail through numerical simulations of the μ c - Si : H p - i - n device. The applicability of the method for other than the investigated devices is discussed with the aid of numerical simulations.