Angermann, H.: Interface states and recombination losses on textured Si substrates after wet-chemical conditioning. In: Progress in applied surface, interface and thin film science - SURFINT SREN III : International Conference, Florence, May 14 - 18, 2012, Italy, 2012. - ISBN 978-80-223-3212-5, p. 19-22
Abstract:
Essential requirement for the manufacturing of economically viable Si-based solar cells is the passivation of Si surfaces and interfaces to reduce recombination loss of light induced charge carriers. This contribution reports on combined optimisation of wet-chemical surface pre-treatment and application of thin passivating layers which are utilised to achieve these goals. The influ-ence of wet-chemical silicon substrate pre-treatments on surface morphology and electronic interface properties is discussed for various hetero interfaces of crystalline Si (c Si) and Si oxides (SiOx), or amorphous materials such as Si (a Si:H), Si nitride (a SiNx:H) and Si car-bide (a SiC:H), which are typically applied in Si heterostructure solar cells. The final aim of the chemical pre-treat¬ments is the removal of damaged regions on textured substrates and the saturation of dangling bonds at the interface/surface by single bonded species (i.e. hydrogen) or well defined and bond angle fitting layers (i.e. wet-chemical oxides). From the viewpoint of global environment conservation, as well as to improve the economics in silicon solar cells manufacturing, the employment of new, highly-efficient cleaning and passivation methods is essential to minimise the chemical consumption and the number of process steps. It was shown that the optimised Si substrate surface state after optimised wet-chemical substrate conditioning can be preserved and transferred into amorphous silicon (a-Si:H)/c-Si, silicon nitride (a-SiNx:H)/c-Si and silicon carbide (a-SiC:H)/c-Si interfaces, typically applied in silicon heterostructure solar cells. The resulting interface recombination losses on the het-ero-junctions prepared by soft a-Si:H deposition were found to be significantly reduced [ ]. According to our results wet-chemical oxidation in hot DIW or in DIW-O3 at ambient tem-perature could be a high quality and low cost alternative to current approaches with liquid chemicals for the preparation of hydrophobic Si substrate surfaces and ultra-thin oxide layers. Sequences of DIW-O3 oxidation and oxide removal in HF containing solutions can be also utilized to reduce Dit on H-terminated substrates, which are predominantly required as starting point for subsequent layer deposition and contact formation.