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.
- This 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.
Report: Advanced High Efficiency Silicon Solar Cells Employing Innovative Atomic Scale Engineered Surface and Contact Passivation Layers
This report discusses the project results and lessons learnt to date for the UNSW Project, Advanced High Efficiency Silicon Solar Cells Employing Innovative Atomic Scale Engineered Surface and Contact Passivation Layers.
How the project works
The Advanced High-Efficiency Silicon Solar Cells project is a collaboration between the two leading Australian academic institutes, UNSW Sydney and the Australian National University (ANU), in the area of carrier-selective contacts with Lead Micro, a leading equipment supplier from China, and Merck Performance Materials.
The project aims at the development of novel carrier selective contacts. This will first be done at the lab scale at UNSW and the ANU and the most promising processes will be transferred to UNSW’s Solar Industrial Research Facility (SIRF). For this purpose, Lead Micro will supply a pilot-scale deposition reactor to UNSW. Finally, the most promising processes will be transferred to leading companies in the photovoltaic industry.
Area of innovation
Carrier-selective contacts are generally considered to be the next critical step for industrial silicon solar cells and are a key component of silicon-based tandem solar cells. This project will explore a wide range of materials at a fundamental level, but will also explore the commercial viability of the developed processes in an academic-industry consortium.
This project is intrinsically aimed at lowering the levelized costs of electricity for solar electricity as the focus is on a cost-effective increase of the solar cell efficiency. Swift transfer to the industry is ensured by a close industry-academia collaboration and by conducting part of the project at the pilot scale level in Australia. The program also allows for training of students and other researchers using industry-scale tools and industry-relevant processes.