Effect of Hydrogen in a-Si:H/c-Si Heterojunction

The photovoltaic characteristics of amorphous/crystalline silicon hetero-junction solar cells are strictly related to the electronic quality of the junction interface. In this paper we investigate the effect hydrogen plasma treatments performed on thin amorphous silicon buffer layer deposited over crystalline silicon surface. In particular we propose the use of surface photovoltage technique as a contact-less tool for the evaluation of the energetic distribution of the state density at amorphous/crystalline silicon interface. The measurement results have been compared with those obtained on the same structure after thermal annealing on the interface. We found that both processes bring to a reduction of the state density of about one order of magnitude, but while the thermal annealing produces a metastable state which goes back to the initial state after just 48 hours, the effect of hydrogen plasma posttreatment results much more stable.