Korean researchers create a perovskite solar cell with record efficiency
Perovskite solar cells (PSCs) are a type of emerging solar cell that uses a perovskite structure crystalline semiconductor as a photoactive layer to convert sunlight into electricity.
Since their discovery in 2009, PSCs have experienced a rapid improvement in their efficiency, quickly outperforming conventional silicon solar cells in terms of solar-to-electricity conversion efficiency.
Recently, a research team led by Professor Sang Il Seok of the Department of Energy and Chemical Engineering at the National University of Science and Technology (UNIST) has presented a new method and principle for controlling the crystallinity of photoactive layer semiconductors of perovskite and has developed a technology to manufacture high-efficiency PSCs.
Record conversion efficiency
As a result of their work, they have achieved a record efficiency of 26.08%, surpassing the efficiency of silicon solar cells.
An achievement that the National Renewable Energy Laboratory has recognized as the best efficiency in the world and that was announced on February 16 in the most prestigious scientific journal in the world, Nature.
“Through this study, perovskite solar cells with an efficiency of more than 26% will soon surpass the efficiency of silicon solar cells,” Professor Seok notes. This study is the starting point of the journey to achieve efficiency greater than 27%.”
The secret behind the success of PSCs lies able to control the crystallization of the perovskite thin film. Internal defects in the crystals of perovskite thin films have a significant impact on the efficiency and long-term stability of solar cells.
Therefore, control of the thin film generation process and understanding the principles of this process are key technologies that satisfy high efficiency and long-term stability at the same time.
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Alkyl ammonium chloride
Alkyl ammonium chloride (RACI) was used to control the crystallinity of perovskite photoactive layer semiconductors.
RACI decomposes in the crystallization step while combining with perovskite components, allowing the rate of solvent volatilization to be controlled during the coating and heat treatment of the perovskite precursor solution.
As a result, it was possible to fabricate a dense perovskite thin film with an extremely flat surface and good crystallinity that minimizes internal crystal defects.
The research team used the UNIST-PAL beamline from the Pohang Accelerator Laboratory to examine the perovskite crystallization process in real-time.
That allowed them to study how halide anions affect perovskite crystallization and how they can control the crystallization process to maximize solar cell efficiency.
Perovskite solar cells still have challenges to overcome
The efficiency of perovskite solar cells has improved significantly in recent years but there are still challenges that need to be overcome before they can compete with large-scale silicon solar cells.
One of the main challenges is the long-term stability of perovskite solar cells. Although PSCs can have high initial efficiency, they can also lose efficiency over time due to the degradation of materials and environmental effects.