In the past, researchers have created a perovskite-based solar cell with more than 25% efficiency, which is comparable to silicon-based solar cells. But, to move these new solar cells beyond the lab, an upscale in size and long-term stability is necessary.

"Lab-scale solar cells are tiny," said Prof. Qi. "The size of each cell is only about 0.1 cm2. Most researchers focus on these because they're easier to create. But, in terms of applications, we need solar modules, which are much larger. The lifespan of the solar cells is also something we need to be mindful of. Although 25% efficiency has previously been achieved, the lifespan was, at most, a few thousand hours. After this, the cell's efficiency started to decline."

Using the synthesized crystalline perovskite powder, Dr. Tong, alongside Research Unit Technician Dr. Dae-Yong Son and the other scientists in Prof. Qi's Unit, achieved a conversion efficiency of over 23% in their solar cell, but the lifespan was more than 2000 hours. When they scaled up to solar modules of 5x5cm2, they still achieved over 14% efficiency. As a proof-of-concept, they fabricated a device that used a perovskite solar module to charge a lithium ion battery.

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%," said Dr. Tong. "One day I hope we can power a building at OIST with our solar modules."

This work was supported by the OIST Technology Development and Innovation Center's Proof-of-Concept Program.