A research team at the Ulsan National Institute of Science and Technology (UNIST) has developed a novel way to manufacture high-efficiency perovskite solar cells (PSCs) by controlling the crystallization behavior of the thin film that coats a crystalline semiconductor of perovskite structure. The team, led by Distinguished Professor Sang Il Seok, developed a technology that uses alkylammonium chloride (RACI) to control the rate of volatilization with solvent during coating and heat treatment of perovskite precursor solution, resulting in a perovskite thin film that is dense, extremely flat, and has very good crystallinity, which minimizes internal defects of the crystal.
The principle was used to manufacture PSCs that achieved the world’s best efficiency of 26.08%, surpassing the efficiency of silicon solar cells. The study was published in Nature, one of the world’s most prestigious magazines, on February 16. The National Renewable Energy Laboratory (NREL) recognized the team’s achievement as the world’s best efficiency of 25.73%.
To achieve high efficiency and long-term stability at the same time, it is crucial to control the defects in the crystals of perovskite thin films. The team’s technology not only enables the control of defects to be extremely low but also has a significant impact on the long-term stability of solar cells.
According to Professor Seok, this study is very meaningful as it examines the crystallization process of perovskite with halide anions in real-time through the UNIST-PAL Beamline of Pohang Accelerator Laboratory. The study is the starting point of the journey to achieve more than 27% efficiency, said Professor Seok, noting that perovskite solar cells with more than 26% efficiency will soon surpass the efficiency of silicon solar cells.
Professor Seok holds the world’s best certified efficiency record, having surpassed the 20% efficiency of PSCs for the first time. He also announced the perovskite heterojunction n-i-p solar cell structure for the first time in the world. More than 25% of high-efficiency perovskite solar cells currently have this structure. He has reported ten papers to Nature and Science, the world’s most prestigious journals, and was selected as a co-winner for the Rank Prize in Optoelectronics in 2022, a renowned science award given by the British Rank Foundation, for his contribution to the creation and development of perovskite solar cells.
The team’s achievement could contribute to the development of clean and renewable energy by providing an efficient and cost-effective way to produce solar cells. The team’s technology can also be applied to other types of thin-film solar cells, including cadmium telluride and copper indium gallium selenide, which are known for their high efficiency but high cost.