Here comes more sun power

Dr. Karin Hinzer

Solar cell technology is proven and popular; now it needs to become more practical. To that end, University of Ottawa researcher Karin Hinzer aims to enhance the efficiency of this high-profile technology, so that it can have an even greater impact on our lifestyle and economy.

“The traditional panels that you buy are a single P-N junction,” she explains. “Light comes into the semiconductor and gets absorbed. The thing is, only part of the solar spectrum gets absorbed.”

Based on the capture of visible light, today’s commercially available panels can reach only 20 per cent efficiency. But with concentrated photovoltaics that take advantage of multi-junctions, which could offer the possibility of collecting energy from a much broader spectrum, that figure could reach 30 per cent or more.

To design these more sophisticated systems, Hinzer needed a more efficient process. A powerful simulation package, Synopsys Sentaurus, can represent the operation of specific components, so their function can be fully understood and optimized. The software can then represent these components in an integrated fashion, to obtain maximum efficiency of their combined functioning. Obtaining this kind of knowledge from manufactured prototypes would be logistically difficult, not to mention exorbitantly expensive.

“You can do trial and error through prototypes, and spend a lot of money,” says Hinzer. “Or, nowadays, simulation tools allow you to design beforehand, and to fix problems.”

She adds that CMC Microsystems has played a key role in providing her with seamless access to these critical simulation tools. The organization, on behalf of its network of researchers, takes care of purchasing and licensing the software which relieves her of a substantial administrative burden. She also has the assurance of working with the latest version of research-critical design products.

In this way, Hinzer and her associates have been able to dedicate more of their attention to the findings from a three-dimensional model of a lattice-matched multi-junction solar cell. The researchers have been able to explore the behaviour of quantum tunnel junctions as a means of transporting electrons between the various layers of a cell.

This work has also confirmed the viability of introducing quantum dots to improve the light-gathering potential of thin-film photovoltaic materials. Growing these nano-scale crystals within the lattice structure of semiconductors makes it possible to tailor the resulting energy level. Hinzer’s team has been able to develop cells with three layers, which respectively respond to infrared, visible, and ultra-violet wavelengths of light.

Hinzer has been working closely with a Toronto-based firm, Morgan Solar Inc., to create the next generation of solar panels for the consumer market. Her university lab is working directly with the company on a system known as Sun Simba, which uses the optical principle of total internal reflection to concentrate the amount of light striking each solar cell. “We did some testing in the lab to show that their technology could work,” she says, describing the collaboration that in 2010 earned an award from the Association of Power Producers of Ontario.

Hinzer, who spent the first half of her career in industry, has been eager to see these innovations become widely available.

Printable version