A team at the Korea Institute of Energy Research (KIER), led by Hong Seong-jun of its Solar Energy Research Laboratory, working with Park Young-seok's group at the Ulsan National Institute of Science and Technology (UNIST) and Lee Kyung-gu's group at Kunsan National University, has developed a "dual-molecule passivation" technique that lifts the power conversion efficiency of inverted perovskite solar cells to 24.6%, more than 3 percentage points above an untreated control cell's 21.21%.
![A solar cell fabricated using dual-molecule passivation technology. [Korea Institute of Energy Research] A solar cell fabricated using dual-molecule passivation technology image](/sites/default/files/2026-08/PSC-made-with-unique-passivation-technique-image.jpg)
The inverted architecture in PSCs, in which the electrode arrangement is reversed relative to the conventional cell design, is particularly well suited to large-area and flexible cells because it allows for low-temperature processing. The persistent obstacle is microscopic defects that form at grain boundaries and on the surface during thin-film fabrication; these trap and scatter electrons and holes as they move through the material, cutting into both efficiency and long-term stability. Conventional passivation coats the perovskite surface with a single type of molecule, which struggles to address the deep grain-boundary defects and the surface defects at the same time.
The team's approach instead applies two organic molecules with different binding behavior, PDAI and 4TF, in sequence, each targeting a different defect type. The smaller PDAI molecules fill the microscopic gaps between grain boundaries to stabilize charge-transport pathways, while 4TF bonds to unstable, dangling lead atoms left on the surface to eliminate additional defect sites.
The complementary treatment measurably outperformed either a bare cell or single-molecule passivation: the dual-molecule-treated cell reached 24.6% power conversion efficiency, versus 23.17% for a cell treated with PDAI alone and 21.21% for an untreated control. The team attributes the gain to the two molecules producing complementary effects, defect elimination and surface stabilization, that neither achieves on its own when applied by itself.
"This achievement is a core foundational technology that will accelerate the commercialization of high-efficiency flexible solar cells for use in building windows, automobile sunroofs and portable devices," said Hong. "We will apply it to a lineup of high-performance next-generation solar cell products to strengthen our technological competitiveness in the eco-friendly renewable energy market."
