Boron-doped a-Si:H∕c-Si interface passivation: Degradation mechanism

The authors report that for a-Si:H∕c-Si heterostructure solar cell fabrication the presence of a boron-doped a-Si:H(p+) overlayer may cause H2 effusion from a (few nanometers) thin underlying intrinsic a-Si:H(i) film at moderate temperatures. This phenomenon is in agreement with losses in the electronic passivation quality of c-Si∕a-Si:H(i)∕a-Si:H(p+) structures occurring during low temperature (⩽260°C) postdeposition annealing. Consequently, it is argued that such passivation degradation is due to Si–H rupture in the a-Si:H(i) film, likely resulting in Si dangling bond defects, mediated by the presence of the doped layer.