Pusan National University researchers improve the stability of perovskite solar cells

Perovskite solar cells are thought of as the strongest contender to replace the conventional silicon solar cells in next-generation photovoltaics. They are made of an A⁺ cation, a B²⁺ divalent cation, and an X^- halide. Generally containing Pb²⁺ or Sn²⁺, they achieve high power conversion energy that is suitable for commercial use. Unfortunately, the presence of lead ions causes issues such as lead leakage, which is a hazard for the environment. Moreover, in the presence of moisture, the perovskite tends to get corroded. Multiple approaches have been suggested to resolve this issue, including encapsulating the device and compositional engineering of the perovskite light absorbers.

Now, a team of researchers from Pusan National University in South Korea have published a study in Volume 92 of the Journal of Energy Chemistry in this direction. It was made available online on 1 February 2024 and has been published in the May 2024 edition. The researchers tested many crown ethers in this study to improve the stability of perovskite solar cells. When asked about the relevance of this study, lead researcher Assistant Professor Ji-Youn Seo from the team says, “This study emphasizes the efficacy of interface passivation by achieving increased power conversion efficiency, and demonstrates that crown ether not only blocks lead leakage through the formation of host-guest complexes with lead ions but also imparts strong resistance to moisture to the treated films, showing improved long-term stability in high humidity environments compared to existing solutions. This research highlights the potential of crown ether to simultaneously address lead leakage and long-term stability for sustainable perovskite solar cells ready to advance commercialization and renewable energy applications.”

The team found that B18C6 was the best ether for interfacial passivation. With B18C6, there was an increased charge carrier lifetime (or the time spent by an electron in the conduction band of a semiconductor and a hole in the valence band of a semiconductor) seen within the perovskite. The work function (or the minimum energy required to move an electron from a metal’s surface) between the hole transfer material and the perovskite was also improved. Thus, the researchers obtained an exceptional power conversion efficiency of 21.7% with B18C6. Compared to untreated perovskites that showed signs of lead leakage, the perovskites with B18C6 showed no signs of lead leakage when a depth profile of all layers was conducted. Furthermore, while normal perovskites showed lead iodide formation when exposed to 95% humidity at room temperature for 300 hours, no such issue was observed for the perovskite passivated by B18C6.

Within the next five years, perovskite solar cell technology, as a type of next generation emerging solar technology, is positioned to potentially replace the globally prevalent silicon solar cells. This technology can enhance photoelectric conversion efficiency to over 30% when used alongside existing silicon solar cells, thereby increasing the possibility of replacing fossil fuel-based energy sources and contributing to the achievement of carbon neutrality. Additionally, perovskite solar cells exhibit superior photoelectric conversion efficiency even under indoor lighting, making them applicable to electronic devices and the Internet of Things (IoT), thus offering significant energy-saving opportunities.

“In ten years, this technology could be applied to the energy, display, and semiconductor materials industries through the heterojunction structure. If leveraged effectively, it could lead to the development of high-efficiency hydrogen production devices, high-brightness, flexible displays, and the development of three-dimensional organic and inorganic semiconductor materials and devices, contributing to leading the advancement of high-tech nations,” says Dr. Seo about the long-term implications of this study.

Here's hoping for the commercialization of perovskites with crown ethers soon!

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Reference

DOI: https://doi.org/10.1016/j.jechem.2024.01.042

Lab website address: https://sites.google.com/view/nemd

ORCID id: 0000-0002-0473-1279

About the institute
Pusan National University, located in Busan, South Korea, was founded in 1946 and is now the No. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service, and has approximately 30,000 students, 1200 professors, and 750 faculty members. The university is composed of 14 colleges (schools) and one independent division, with 103 departments in all.

 Website: https://www.pusan.ac.kr/eng/Main.do

About the author
Prof. Ji-Youn Seo is an Assistant Professor of Nanoenergy Engineering and Vice leader of Semiconductor Process & Equipment Contract Department at Pusan National University. Her group is developing approaches to control crystallization and defect level through molecular engineering technology for Perovskite Solar Cells. Seo group is also developing eco-friendly technology such as water splitting for hydrogen generation and metal-organic frames (MOFs) for CO₂ capture. Before coming to Pusan National University, she received her BSc & MS degrees in Ajou University in 2009 & 2011 and her PhD degree from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland under the supervision of Prof. Michael Grätzel. She also has industry experiences, Hyundai Motor Company (HMC) in Korea and H.GLASS in Switzerland. She was working to develop eco-friendly technology in both company such as bio-plastics, fuel cell in HMC and OPV & Dye-sensitized Solar Cell in H.GLASS