- Demonstrates 1,000 hours of stability under extreme conditions of 85°c and 85% humidity

  The research team led by Professor Min Kim of the Department of Chemical Engineering at the University of Seoul conducted a joint study with the teams of Professor Jaewon Lee of Chungnam National University and Professor JungYup Yang of Kunsan National University. The team announced that the resulting paper was published in Advanced Functional Materials (IF 18.5, top 4.8% in JCR), a globally renowned journal in materials science, and was selected as the Inside Back Cover article for the issue. 

  The paper is titled “Cyclic Structured Ionic Molecules Formulating Multi-Dimensional Perovskite Structures of Highly Stable and Efficient Perovskite Solar Cells.” In this study, researchers Jeongbeom Cha of the Department of Intelligent Semiconductor Engineering at the University of Seoul, Dohun Baek of the Department of Chemical Engineering at the University of Seoul, and Jaegwan Shin of Kunsan National University participated as co-first authors and played key roles. 

  Perovskite solar cells (PSCs) have emerged as a promising candidate for next-generation solar cells, achieving power conversion efficiencies exceeding 26%. However, most existing studies rely on strictly controlled inert atmospheres with humidity below 30% and on toxic solvents (e.g., chlorobenzene, diethyl ether), which impose limitations on large-scale production and commercialization.

  Ethyl acetate, an eco-friendly solvent that has attracted attention as an alternative, is suitable for ambient-condition processing; however, its high volatility leads to irregular crystallization. As a result, defects and pinholes form in the film, significantly reducing device efficiency and stability.

  To address these issues, the joint research team designed two N-heterocyclic ammonium ionic liquids with tunable ring sizes. By incorporating a five-membered ring pyrrolidinium cation and a six-membered ring piperidinium cation into the ethyl acetate solvent, the team demonstrated that high-quality perovskite thin films can be fabricated even under ambient conditions with relative humidity below 50%.

  Consequently, the smaller-ring cation formed an ultrathin low-dimensional (2D) perovskite layer at the interface, enhancing perovskite crystal orientation, suppressing trap states, and simultaneously inducing beneficial in-plane compressive lattice strain, thereby enabling the formation of high-quality thin films with excellent crystallinity. Perovskite solar cells incorporating this material achieved a maximum power conversion efficiency of 24.7% and demonstrated outstanding durability, retaining over 90% of their initial efficiency even after 1,000 hours under harsh high-temperature and high-humidity conditions (85°C/85% relative humidity).

  This study is evaluated as a significant step toward commercialization, in that it presents an environmentally friendly and scalable process for fabricating high-efficiency and high-stability perovskite solar cells without the use of toxic solvents or inert atmospheres. In particular, the strategy of systematically controlling the ring size of ionic liquids is broadly applicable to various perovskite systems and is expected to enable future applications in next-generation solar cells and light-emitting devices.

▶ From left: Jeongbeom Cha (doctoral student, University of Seoul), Professor Min Kim, Professor Jaewon Lee (Chungnam National University), and Professor Jungyup Yang (Kunsan National University).

  “This research achievement significantly improved the crystallinity of perovskite thin films and the performance of solar cells through the introduction of eco-friendly solvents and ionic liquid molecules,” stated Professor Min Kim. “It presents a key strategy that accelerates the practical application of high-efficiency and high-stability perovskite solar cells.”

  This research was conducted with support from the Early Career Research Grants Program of the National Research Foundation of Korea (NRF) under the Ministry of Science and ICT, as well as the Ministry of Trade, Industry and Energy.