Restoring quantum dot solar cells as if ‘flattening crumpled paper’

(Nanowerk News) Professor Jongmin Choi’s team from the Department of Energy Science and Engineering at DGIST conducted joint research with Materials Engineering and Convergence Technology Professor Tae Kyung Lee from Gyeongsang National University and Applied Chemistry Professor Younghoon Kim from Kookmin University. The researchers developed a new method to improve both the performance and the stability of solar cells using “perovskite quantum dots.” They developed longer-lasting solar cells by addressing the issue of distortions on the surface of quantum dots, which deteriorate the performance of solar cells. The research findings were published in Chemical Engineering Journal (“Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots”). A schematic diagram of bilateral ligand bonding on the surface of perovskite quantum dots. (Image: DGIST) Perovskite quantum dots are critical materials for next-generation solar cells. They have excellent light-to-electricity conversion capabilities and are easy to mass-produce. However, to utilize them in solar cells, the “ligands” attached to the quantum dot surface must be replaced. This process often leads to distortions of the quantum dot surface, resembling crumpled paper, which results in decreased performance and shorter lifespans for the solar cells. To address this issue, Professor Jongmin Choi’s team newly adopted short ligands that securely hold the quantum dots from both sides, effectively uncrumpling the distorted surface. The ligands help restore the distorted lattice structure, smoothing the crumpled surface of the quantum dots. This significantly reduces surface defects, enabling the solar cells to operate more efficiently and extending their lifespan. Consequently, the power conversion efficiency of the solar cells increased from 13.6% to 15.3%, demonstrating stability by maintaining 83% of their performance for 15 days. “Through this research, we could minimize surface defects on the quantum dots and stabilize their surfaces by newly adopting these amphiphilic ligands, thereby significantly improving the efficiency and stability of the solar cells,” said Professor Jongmin Choi from the Department of Energy Science and Engineering at DGIST. “We plan to continue our research on stabilizing the surface of perovskite quantum dots, hopefully applying the results to various photoelectric devices.” This study was a joint effort by the research teams of DGIST Professor Jongmin Choi, Gyeongsang National University Professor Tae Kyung Lee, and Kookmin University Professor Younghoon Kim, led by Gayoung Seo and Sanghun Han from DGIST, along with Donggyu Lee, a Ph.D. candidate from Gyeongsang National University. The study was supported by the National Research Council of Science & Technology’s Creative Convergence Research Project, the DGIST R&D Program, and the New Faculty Research Foundation Project at Gyeongsang National University.