Researchers at KAIST have solved the "solar cell dilemma" — where improving efficiency shortens lifespan, and extending lifespan reduces efficiency. The team developed a technology that precisely controls the internal structure of a protective layer on perovskite solar cells, simultaneously achieving high efficiency above 25% and long-term stability.
KAIST announced on the 24th that a research team led by Chair Professor Seo Jang-won of the Department of Chemical and Biomolecular Engineering developed a two-dimensional (2D) protective layer design technology that simultaneously improves the efficiency and long-term stability of perovskite solar cells through joint research with the Korea Research Institute of Chemical Technology (KRICT), headed by Director Lee Young-guk.
As the demand for climate crisis response and energy transition grows, improving solar power generation efficiency and securing long-term reliability have emerged as critical challenges. Perovskite solar cells, which have attracted attention as next-generation high-efficiency solar cells, have seen rapid efficiency improvements recently. However, performance degradation under high-temperature, high-humidity environments or prolonged light exposure has been cited as a barrier to commercialization.
Previously, a "3D/2D structure" strategy was used, in which a two-dimensional (2D) layer is coated on top of three-dimensional (3D) perovskite crystals. This method helps reduce surface defects and improve stability. However, if the 2D layer's structure is not sufficiently robust, it can deform over time or gradually lose performance.
The research team introduced a structurally more stable Dion–Jacobson (DJ) structure for the 2D perovskite protective layer and presented a design strategy to precisely control the "n-value," which indicates how many perovskite layers are stacked within the protective layer. The DJ structure enhances structural stability by having organic molecules firmly connect both sides between perovskite layers — similar in principle to binding bricks with a stronger adhesive so the structure does not collapse easily.
The team controlled the stacking structure (n-value) of perovskite layers within the 2D protective layer to the desired configuration by adjusting heat treatment conditions — much like controlling the temperature and time during the curing process after stacking bricks to make the structure stronger and more orderly.
As a result, charge transport became smoother, improving solar cell efficiency, and long-term stability also improved thanks to the robust characteristics of the DJ structure. The team also experimentally revealed that the internal structure of the 2D protective layer changes as structural rearrangement occurs at the interface where different materials meet during the heat treatment process, presenting both the underlying principles for controlling the protective layer structure and reproducible process conditions.
The perovskite solar cell applying this design strategy recorded a high power conversion efficiency of 25.56% (certified efficiency of 25.59%). It also maintained high performance under conditions of 85°C and 85% relative humidity (85% RH) and continuous light irradiation, confirming long-term stability. The research team also applied this technology to large-area module fabrication and confirmed excellent performance.
"This research demonstrates that the longstanding challenge — where improving efficiency reduces lifespan and extending lifespan lowers efficiency — can be solved simultaneously through the structural design of the surface protective layer," Chair Professor Seo Jang-won said. "This technology operates relatively stably even with changes in process conditions, which could also benefit large-area manufacturing processes for commercialization."
The research, co-first-authored by Lee Jae-hee, an integrated M.S./Ph.D. student in KAIST's Department of Chemical and Biomolecular Engineering, and Dr. Moon Chan-su of the Korea Research Institute of Chemical Technology, was published in Joule (IF 35.4), one of the most prestigious journals in the energy field, in the February 24, 2026 issue.