A research team led by Dr. Sungjun Hong of the Photovoltaics Research Department at the Korea Institute of Energy Research (KIER) has developed a dual-molecule passivation technology that simultaneously improves the efficiency and stability of inverted perovskite solar cells. The research was conducted in collaboration with Professors Young Seok Park of Ulsan National Institute of Science and Technology (UNIST) and Professor Kyung-Koo Lee of Kunsan National University.
Perovskite solar cells are attracting significant attention as a next-generation photovoltaic technology because they are lightweight and relatively easy to manufacture. However, during thin-film fabrication, microscopic defects can form at grain boundaries and surfaces, causing charge carriers to recombine before they can contribute to electricity generation. In particular, inverted perovskite solar cells, which can be fabricated at relatively low temperatures and are therefore advantageous for commercialization, have faced surface defects as a major barrier to further performance improvements.
To address these defects, conventional approaches have mainly relied on passivation, in which an ultrathin molecular layer is applied to stabilize the perovskite surface. However, because most existing techniques use only a single type of molecule, it has been difficult to simultaneously passivate defects located deep within grain boundaries and those present directly on the surface.
Moving beyond conventional single-molecule approaches, the research team introduced a dual-molecule strategy that combines two organic molecules with different binding characteristics.
Similar to filling gaps with two differently shaped building blocks, the researchers first used the smaller PDAI molecule to fill microscopic voids remaining at grain boundaries and stabilize charge-transport pathways. They then applied 4TF molecules, which bond with undercoordinated lead atoms remaining on the perovskite surface. This chemically stabilized the surface and facilitated more efficient charge transport.
As a result, the newly developed solar cell achieved a power conversion efficiency of 24.6%, significantly higher than that of the untreated control device (21.21%) and the device treated with PDAI alone (23.17%). The researchers also experimentally demonstrated that sequentially applying the two molecules produces complementary effects in defect passivation and surface stabilization, resulting in better performance than using either molecule independently.
Dr. Hong, who led the study, said, “This technology provides a key fundamental platform for accelerating the commercialization of high-efficiency, flexible solar cells for applications such as building windows, automotive sunroofs, and portable devices.” He added, “We plan to expand its application to a broader range of high-performance next-generation solar cell products and strengthen technological competitiveness in the clean and renewable energy market.”
The research was supported by KIER’s principal research program and was published online in April 24 in the internationally renowned journal ACS Applied Materials & Interfaces (Impact Factor: 7.8).