Advanced High-Efficiency Silicon Solar Cells

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In this Advanced High-Efficiency Silicon Solar Cells project, we exploit the unique capabilities of Atomic Layer Deposition (ALD) to synthesise innovative surface and contact passivating stacks.ALD allows the synthesis of multilayer structures that can be tailored at the atomic scale towards desired material properties such as work function, interface defect density, and conductance. Our particular focus is on increasing the selectivity of electron and hole contacts. The higher the selectivity of a contact, the higher the efficiency potential of the solar cell. The current contact systems used in Passivated Emitter Rear Cell (PERC) solar cells have a selectivity of 12 and 13 for holes and electrons, respectively, and this project aims to develop electron and hole contacts with higher selectivity and thus higher efficiency ceilings. These contacts can also be used for future silicon- based tandem solar cells.Key resultsThis project brought together the academic Australian leaders in the field of atomic layer deposition (ALD) and novel passivated contacts with a leading equipment manufacturer ensuring fast transfer of project results to the industry.The project made significant progress in the development of passivation contacts. It demonstrated that the most promising electron selective contact titanium oxide could be improved by doping the layer with aluminium. Aluminium doping improved both the contact properties as well as the level of surface passivation, resulting in an improved selectivity. In addition, the layer had an improved thermal stability.The project also made progress with passivating hole contacts by improving the performance of nickel oxide by doping the film with zinc. The addition of zinc significantly improved the contact between nickel oxide and silicon. In addition, the nickel oxide layer was also more thermally stable.After adding a hydrogenated amorphous silicon interface passivation layer, the project achieved a contact with a selectivity of 15, which is among the most promising passivating hole contacts developed to date delivered at lower cost than similar projects.The project showed that ALD layers can effectively protect solar cells against potential induced degradation. The researchers were also able to synthesise graphene directly on ALD nickel oxide, solving a critical technology barrier for the application of graphene films by using a functional layer as the catalyst for the graphene growth.

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