Industry Ready N-Type Silicon Solar Cells

Project innovation

Cost remains the key barrier to the widespread uptake of solar cells. Through this project, researchers aim to significantly increase the amount of energy a solar cell can convert from sunlight (called efficiency) without extra manufacturing costs per cell.

This will be done by combining the existing fast and inexpensive methods used to make today’s standard silicon solar cells (using p-type silicon) with the latest advances in high efficiency silicon solar cells (using n-type silicon).

The Industry Ready N-Type Silicon Solar Cells project conducted two parallel research activities involving high efficiency n-type silicon solar cells that aim to drive down the cost of photovoltaic (PV) modules to the point where solar electricity is competitive with that generated by conventional power stations. N-type silicon has been shown to have a much greater tolerance to the efficiency-limiting impurities that are common in standard p type silicon cells.

Firstly in collaboration with Trina Solar, researchers developed low-cost 20% efficient n type solar cells using mono-crystalline silicon, and also improved their standard p-type multi-crystalline silicon solar cells to 21.6% in the lab and 20.5% on large scale cells produced at Trina. These values are well above the standard cell efficiencies of 19% efficiency. These advances were based on new ways to prepare and coat the surfaces of p-type solar cells, and the use of innovative surface designs to reduce the amount of reflected light.

Secondly, in collaboration with University of New South Wales, researchers developed advanced industry-ready n-type solar cells with efficiencies well above 23% using innovative but high throughput techniques such as liquid-jet laser doping, and sputtering for thin-film deposition. Liquid-jet laser doping was successfully used to fabricate 20.0% efficient double-sided contact solar cells.

Benefit

Successful execution of the project will reduce the price of PV modules and accelerate the global uptake of PV.

The project has created innovations for future exploitation, and help ensure Australian researchers remain at the very forefront of research and development in silicon photovoltaics.

Achievements and lessons learned

The complexity and reliability of laser-based doping technique for double-sided contact solar cells are likely to be significant barriers to the use of this approach in industry. The use of amorphous silicon layers deposited by sputtering was shown to have promise as a low-cost method for hybrid amorphous/crystalline silicon solar cells, although further development is required. The project was effective in building a strong partnership between ANU and Trina Solar, which will act as a foundation for expanded collaboration in the future.

The project was also effective in developing new and innovative methods for reducing the complexity and cost of the n-type cell process, which necessarily involves more fabrication steps than the equivalent p-type process.

There were, however, some significant challenges in transferring the techniques developed in the laboratories at ANU to the industrial setting in Trina Solar, due to the fact that the methods and equipment at the two organisations are in some cases quite different. Future projects of this nature would benefit from the availability of more industrially compatible equipment at ANU.

The project has resulted in the development of new methods for accurately measuring the electronic quality of locally doped regions of solar cells. These methods will be valuable in the development of other silicon solar cell technologies at ANU and elsewhere.

The project has also advanced ANU’s cell fabrication capabilities to a new level, which will have broader benefits across our large research team for years to come. The use of ion implantation and sputtering for rear contact solar cells could also be broadened to other cell designs, such as the traditional two-sided metal contact design.

Final report

This project has successfully developed new technologies for n-type silicon solar cells with efficiencies well above 20%, and which are compatible with mass production. Transfer of these technologies to industry will therefore help to further drive down the cost of PV modules in terms of $/Watt, making solar electricity more affordable, and more competitive with conventional electricity sources.