高清福利片

Australian scientists have for the first time produced a new generation of experimental solar energy cells that pass strict testing standards for heat and humidity.

The research findings, an important step towards commercial viability of perovskite solar cells, are published today in the journal .

Solar energy systems are now widespread in both industry and domestic housing. Most current systems rely on silicon to convert sunlight into useful energy.

However, the energy conversion rate of silicon in solar panels is close to reaching its natural limits. So, scientists have been exploring new materials that can be stacked on top of silicon in order to improve energy conversion rates. One of the most promising materials to date is a metal halide perovskite, which may even outperform silicon on its own.

鈥淧erovskites are a really promising prospect for solar energy systems,鈥� said Professor Anita Ho-Baillie, the inaugural John Hooke Chair of Nanoscience at the University of Sydney. 鈥淭hey are a very inexpensive, 500 times thinner than silicon and are therefore flexible and ultra-lightweight. They also have tremendous energy enabling properties and high solar conversion rates.鈥�

In experimental form, the past 10 years has seen the performance of perovskites cells improve from low levels to being able to convert 25.2 percent of energy from the Sun into electricity. It took about 40 years for scientists to develop silicon-cell conversion rates of 26.7 percent.

However, unprotected perovskite cells do not have the durability of silicon-based cells, so they are not yet commercially viable.

鈥淧erovskite cells will need to stack up against the current commercial standards. That鈥檚 what is so exciting about our research. We have shown that we can drastically improve their thermal stability,鈥� Professor Ho-Baillie said.

The scientists did this by suppressing the decomposition of the perovskite cells using a simple, low-cost polymer-glass blanket.

The work was led by Professor Ho-Baillie who joined the University of Sydney Nano Institute this year. Lead author, , conducted the experimental work in Ho-Baillie鈥檚 research group in the School of Photovoltaic and Renewable Energy Engineering at the University of New South Wales, where Professor Ho-Baillie remains an adjunct professor.

Under continual exposure to the Sun and other elements, solar panels experience extremes of heat and humidity. Experiments have shown that under such stress, unprotected perovskite cells become unstable, releasing gas from within their structures.

鈥淯nderstanding this process, called 鈥榦utgassing鈥�, is a central part of our work to develop this technology and to improve its durability,鈥� Professor Ho-Baillie said.

"I have always been interested in exploring how perovskite solar cells could be incorporated into thermal insulated windows, such as vacuum glazing. So, we need to know the outgassing properties of these materials.鈥�

Low-cost solution

For the first time, the research team used聽聽(GC-MS) to identify the signature volatile products and decomposition pathways of the thermally stressed hybrid perovskites commonly used in high-performance cells. Using this method, they found that a low-cost polymer-glass stack with a pressure-tight seal was effective in suppressing the perovskite 鈥榦utgassing鈥�, the process that leads to its decomposition.

When put to strict international testing standards, the cells the team was working on outperformed expectations.

鈥淎nother exciting outcome of our research is that we are able to stabilise perovskite cells under the harsh International Electrotechnical Commission standard environmental testing conditions. Not only did the cells pass the thermal cycling tests, they exceeded the demanding requirements of damp-heat and humidity-freeze tests as well,鈥� Professor Ho-Baillie said.

These tests help determine if solar cell modules can withstand the effects of outdoor operating conditions by exposing them to repeated temperature cycling between -40 degrees and 85 degrees, as well as exposure to 85 percent relative humidity.

Specifically, the perovskite solar cells survived more than 1800 hours of the IEC 鈥淒amp Heat鈥� test and 75 cycles of 鈥淗umidity Freeze鈥� test, exceeding the requirement of聽聽standard for the first time.

鈥淲e expect this work will contribute to advances for stabilising perovskite solar cells, increasing their commercialisation prospects,鈥� Professor Ho-Baillie said.

Declaration

This research was supported by the Australian Government through the Australian Renewable Energy Agency (ARENA).