Low-temperature atomic layer deposition of MoO_x for silicon heterojunction solar cells

The preparation of high-quality molybdenum oxide (MoO_x) is demonstrated by plasma-enhanced atomic layer deposition (ALD) at substrate temperatures down to 50 C. The films are amorphous, slightly substoichiometric with respect to MoO₃, and free of other elements apart from hydrogen (<11 at%). The films have a high transparency in the visible region and their compatibility with a-Si:H passivation schemes is demonstrated. It is discussed that these aspects, in conjunction with the low processing temperature and the ability to deposit very thin conformal films, make this ALD process promising for the future application of MoO_x in hole-selective contacts for silicon heterojunction solar cells. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)