A Japanese research team have successfully devised a method to create one of the elusive materials that is vital in the production of perovskite solar cells.
The team, comprised of scientists from the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University, have successfully developed an innovative method for fabricating a critical raw material in the production of perovskite solar cells, potentially advancing the next generation of green energy solutions.
The team’s study is published in Nano Energy.
How would the production of perovskite solar cells revolutionise the energy sector?
Perovskite solar cells have the aptitude to transform the renewable energy industry, alleviating the global dependence on otherwise environmentally harmful energy sources, such as the burning of finite fossil fuels. Ensuring the efficient production of perovskite solar cells may be our most promising breakthrough in achieving future sustainable energy source, as they, unlike other methods, are powered by the infinite source of power attainable to humanity, the Sun.
By converting sunlight into electricity, perovskite collar cells can have a variety of applications, and once upscaled from their diminutive size, can be made into modules, which can be used to charge batteries and power lights, with the potential to be the main energy source for buildings in the future. However, the traditionally utilised material in making solar cells is silicon, making them uneconomical to manufacture compared to other sources of energy.
Contrastingly, the principal material in the production of perovskite solar cells – metal halide perovskite – bring forward a more financially beneficial alternative, efficiently converting sunlight to energy but at a fraction of the cost. Perovskite solar cells have a range of extra benefits, with their rigid and limber substrate composition making them light and malleable, although to see wide-scale production, they will need to be increased in size, lifespan, and efficiency.
Dr Guoqing Tong, the Postdoctoral Scholar in the Unit, said: “There’s a necessary crystalline powder in perovskites called FAPbI3, which forms the perovskite’s absorber layer. Previously, this layer was fabricated by combining two materials – PbI2 and FAI. The reaction that takes place produces FAPbI3. But this method is far from perfect. There are often leftovers of one or both of the original materials, which can impede the efficiency of the solar cell.”
Designing a new strategy
To navigate this impediment, the team employed a more precise powder engineering method to synthesise the crystalline powder, still using one of the PBI2, but carrying out additional steps to ensure that the finished powder was of exceptional quality and structurally perfect, achieving this by heating the mixture to 90 degrees Celsius and purifying out any leftovers.
The novel method increased the stability of the perovskite across different temperatures, as although its absorber layer was stable at high temperatures, it turned from brown to yellow at room temperature, reducing its capabilities of absorbing light, whereas the synthesised version remained brown at room temperature. Furthermore, despite researchers previously creating perovskite solar cells with efficiency exceeding 25% – similar to silicon-based cells – to become viable on a commercial scale, they will need to be upscaled in terms of size and long-term stability.
“There’s a necessary crystalline powder in perovskites called FAPbI3, which forms the perovskite’s absorber layer,” explained Professor Yabing Qi, the leader of the study . Previously, this layer was fabricated by combining two materials – PbI2 and FAI. The reaction that takes place produces FAPbI3. But this method is far from perfect. There are often leftovers of one or both of the original materials, which can impede the efficiency of the solar cell.”
The synthesised crystalline perovskite powder displayed a conversion efficiency of over 23% within their solar cell, demonstrating a lifespan of more than 2000 hours, achieving an efficiency of over 14% when the solar module was upscaled to 5x5cm2.
Dr Tong said: “These results represent a crucial step towards efficient and stable perovskite-based solar cells and modules that could, one day, be used outside of the lab. Our next step is to make a solar module that is 15x15cm2 and has an efficiency of more than 15%. One day I hope we can power a building at OIST with our solar modules.”
