Organized chaos: the key to next generation solar technology

Hidden inside the meteorite structure it can be the inspiration for our renewable energy needs.

Known as perovskite, the mineral was first discovered in the Urals of Russia by Gustav Rose in 1839 and was named after the Russian mineralogist LA Perovski.

Today, a perovskite is any material with a mineral-like crystal structure called perovskite, but most of it is artificially synthesized in the laboratory.

Many scientists and engineers working in solar energy have focused on perovskite materials because their crystalline structure can act as a semiconductor for passing current and absorbing visible light.

In the 21st century, perovskites have shown great potential in several important applications, including LEDs (light-emitting devices), fast X-ray imaging machines, lasers. They also have applications in photoelectrolysis – the process of using light to split water – which could have an important role to play in producing low- or zero-emission hydrogen for power generation and, consequently, green heavy industry. and production.

But perhaps the greatest excitement surrounds the potential for perovskites to supplement or, in some cases, replace silicon as a key component in converting light to electricity, a field known as photovoltaics.

Silicon has allowed individual homeowners, businesses and energy companies to install large-scale solar panels over the past few decades, but the material also has some drawbacks.

Creating silicon solar cells requires significant amounts of energy, often generated by burning fossil fuels, and they are fundamentally limited in efficiency when converting sunlight into energy.

At the end of their life cycle, silicon solar cells are also expensive to recycle.

This is where perovskites come into play.

Unlike silicon, perovskite materials are easy and inexpensive to create, both in terms of time and cost. They are also more flexible than silicone and in some cases can be printed on a base material, not unlike the way ink is printed on paper.

The perovskites also demonstrated an efficiency comparable to silicon. They’re also customizable, which means they can be “tuned” to take advantage of parts of the light spectrum that silicon can’t capture.

Their properties raise the prospect that tandem solar cells – devices containing both silicon and perovskite – will be distributed commercially, offering significant increases in efficiency and productivity over existing solar cells.

However, there are a number of challenges that prevent you from realizing all of this exciting potential.

One such problem is a phenomenon known as light-induced phase segregation, in which sunlight disrupts the initially uniform arrangement of halide ions (a negatively charged halogen atom such as bromide and iodide) within perovskites .

This leads to perovskite instability bandgap, the energy gap between occupied and empty energy levels, which affects which part of the solar spectrum can be absorbed. These changes occur unevenly across the perovskite, which slows the movement of electrons through the material and reduces the efficiency of the devices.

A solar cell that malfunctions in sunlight isn’t much use to anyone, so scientists have worked hard to clear up this annoying flaw in the otherwise promising future of solar PV.

And now an effective, albeit ironic, solution has been found.

With our colleagues at the ARC Center of Excellence in Exciton Science, we have shown that increasing light intensity beyond the range that a rooftop solar cell would normally experience will cancel out the noise introduced at lower light intensities and that this approach can be used to control the bandgap of the material.

This mechanism was unexpectedly noticed during a recent investigation and required complex computational modeling to be understood before the results could be shared.

Many of the previous efforts to solve this phase segregation have involved changing the type of material, its composition or its size, with the decisive role of light intensity hitherto gone unnoticed.

The phenomenon can be thought of as a dimmer switch telling the bromide and iodide what to do. By turning the control knob to a super bright level, the cluttered elements will return in a controlled pattern.

To achieve this in a real-world environment, a tool such as a solar concentrator would be needed, which uses focused sunlight to increase the power of the sun.

The results, which were published in the journal Natural materials, should prompt further large-scale investigations by research groups around the world into the potential of this new approach.

Perhaps the most important implication is the fact that the best combination and arrangement of elements in the material can be maintained to achieve high efficiency and control, without the need for any external treatment or chemical “doping” of the material.

But it’s not just the solar energy field that benefits. Using light to quickly change the bandgap of a semiconductor material has other practical applications, including data storage.

The future looks promising for the Perovskites and it just needs a little more light to show us the way.

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