Spectral variations in the optical transition matrix element and their impact on the optical properties associated with hydrogenated amorphous silicon

► The spectral dependence of the a-Si:H optical transition matrix element is determined. ► The spectral dependence of the imaginary part of the dielectric function is then determined. ► A selection of the mobility gap was shown to be inconsistent with experimental data. ► We used this data in order to determine an upper bound on the mobility gap associated with a-Si:H. ► Electrical measurements yielded mobility gap values consistent with this bound.