Australian researchers show next gen solar cells can beat the heat

Australian researchers have demonstrated that new solar panel designs and manufacturing techniques have the potential to solve some of the key challenges of operating in high temperatures, showing that they not only produce more useful electricity but have longer operational lives thanks to their ability to beat the heat.

In new research published in the journal Progress in Photovoltaics, researchers at UNSW Sydney have shown that next-generation solar cell designs have the ability to achieve lower operating temperatures, allowing the cells to maintain higher efficiencies and slow down heat-related degradation.

Key to the improved performance is a combination of two features of next-generation solar cells – a technique called singlet fission and the production of tandem solar cells.

Researchers have explored the production of ‘tandem’ solar cells, which consist of two different types of solar cells layered on top of each other. A common example is next-generation perovskite solar cells that are layered on top of a conventional silicon solar cell. By combining two types of solar cells together, it is possible to convert more of the light spectrum into useful electricity, boosting the solar cell’s overall efficiency.

Tandem solar cells have been promoted as a way to overcome the technical limitations of conventional silicon cells, by using a perovskite layer that can convert sunlight into electricity that would otherwise go unused by a silicon cell.

Singlet fission has also attracted the interest of researchers as another way to squeeze more useful energy out of sunlight.

In conventional solar cells, a unit of light, known as a photon, transfers energy to an electron and allows for an electric current to be produced. By incorporating the singlet fission technique in solar cell design, a single photon can be used to deliver energy to two electrons within solar cell material. By delivering energy to twice as many electrons, singlet fission can also provide a pathway to more efficient solar cells by allowing more of the sun’s energy to be captured.

While it is well understood by researchers that each of these techniques can boost the maximum conversion efficiencies of solar cells, the research team based at UNSW Sydney say that they have been able to show the additional ancillary benefits of improved heat performance and lower operating temperatures.

As is common with other semiconductor technologies, solar cells can suffer a drop off in performance as their temperature increases. In other applications of semiconductors, such as computer processors, great lengths are taken to ensure that the devices are kept as cool as possible.

But this can be a challenge for solar cell technologies, the whole purpose of which is to be directly exposed to the sun on a daily basis. As temperatures increase, the efficiency of solar cells generally drops, reducing the amount of useful electricity produced. Long-term exposure to high temperatures can also limit the useful life of solar cells, with heat being a key contributor to solar cell degradation.

The new solar cell design techniques, the researchers have shown, allow for solar cells with higher performance – converting sunlight into a greater amount of useful electricity – as well as allowing for longer-lasting solar panels.

Researchers pointed to the benefits of lower operating temperatures for solar cells, with a 5 to 10-degree decrease in solar cell operating temperature corresponding to a 2 to 4 per cent increase in electricity production.

Likewise, reduced operating temperatures can extend the life of solar cells, with the use of tandem cells designs increasing the life of solar cells by an average of 3.1 years and singlet fission cells lasting up to 4.5 years longer.

Lead author of the study, Dr Jessica Yajie Jiang, said that the use of new techniques that can deliver improved heat performance would be key to the widescale use of next-generation solar cell designs in commercial deployments.

“The commercial value of photovoltaic technologies can be increased by either increasing the energy conversion efficiency or the operational lifespan,” she said. “The former is the primary driver for the development of next-generation technologies, while little thought has been given to the potential lifespan advantages.

“We demonstrated that these advanced photovoltaic technologies also show ancillary benefits in terms of enhanced lifespan by operating at lower temperature and more resilience under degradation, introducing a new paradigm to evaluate the potential of new solar energy technologies.”

The research was undertaken by the School of Photovoltaic and Renewable Energy Engineering and the ARC Centre of Excellence in Exciton Science, which are both based at the UNSW campus in Sydney.