Development and application of low temperature magnetron sputtered ITO thin films for a-Si:H based junction solar cells

This paper reports on the optimization of ITO films deposited by RF magnetron sputtering method from In₂O₃/SnO₂ target. In view of the application of this transparent conductive oxide as top layer in amorphous and a-Si/c-Si heterojunction solar cells, low temperature and low sputtering power have been selected in order to avoid damages of underlying device. Transition of ITO from amorphous to mixed amorphous/crystalline phase has been observed at room temperature with increasing deposition power. Low resistivity amorphous oxide layers (2.8·10^-4 Ω·cm) have been achieved at low RF power density. Optical transmittance of this film stays above 82% in the visible range. a-Si:H p-i-n and a-Si/c-Si heterojunction solar cells with 9.4% and 14.5% efficiency respectively have been realized with this ITO as top electrode, after device thermal annealing at 150°C