"In the early stages of perovskite solar cell development, the benchmark for evaluating achievement was 'by how many percentage points the photoelectric conversion efficiency was dramatically improved over previous research.' However, now that efficiency improvements are approaching theoretical limits, research into 'stability' — including practical use in space — has become far more important."
Seo Jang-won (pictured), distinguished professor in the Department of Chemical and Biomolecular Engineering at the Korea Advanced Institute of Science and Technology (KAIST), said in a Seoul Economic Daily interview conducted at his KAIST laboratory in Yuseong-gu, Daejeon on the 3rd of this month that interest in perovskite solar cell technology, known as the "third-generation solar cell," is higher than ever. Perovskite solar cells use semiconductor materials with a "perovskite structure" as the light absorption layer instead of silicon. They are much thinner and more flexible than conventional silicon solar cells and also offer superior energy conversion efficiency.
In particular, as SpaceX — the space company led by Elon Musk — prepares for its initial public offering (IPO), Musk's reference to perovskite materials as "the key to space solar power" has once again drawn public attention. Amid growing anticipation for a "space manufacturing supercycle," driven by SpaceX's plans to build solar-powered space data centers and the U.S.-China space race, advancing perovskite solar cell technology to maintain long-term performance even in the extreme environment beyond Earth is becoming increasingly important.
In Professor Seo's lab, the process of manufacturing and verifying the performance of perovskite solar cells using new design technology was actively underway. A square substrate, 2.5 cm on each side and containing three-dimensional (3D) perovskite crystals, was placed on a rapidly rotating "spin coater." When a drop of organic cation precursor solution was added, centrifugal force instantly spread it across the entire plate. Then, when the substrate was placed on a hot plate at over 100°C, the solution quickly settled into a two-dimensional (2D) coating film. This coating reduces defects on the surface of the light absorption layer and mitigates efficiency degradation even after prolonged exposure to high-temperature environments.
Professor Seo explained, "This protective layer is precisely what distinguishes our research from previous studies." Previously, 2D protective layers were formed with a Ruddlesden-Popper (RP) structure, which had the problem of easily deforming over time or at high temperatures. In response, the research team, in a joint study with the Korea Research Institute of Chemical Technology, introduced the Dion-Jacobson (DJ) structure to make the perovskite layer's structure more robust. While the RP structure has relatively weak bonding between protective layers, the DJ structure uses organic molecules that act as "bridges" tightly holding the layers together in both directions, making it far more resistant to heat and shock. The perovskite solar cell applying this design strategy achieved a high photoelectric conversion efficiency of 25.56%. The theoretical limit for a single-junction perovskite solar cell is in the low 30% range.
Technologies that enhance the durability of the perovskite solar cell itself, such as the protective layer design, are essential for the space solar power business. Currently, the most acclaimed solar cell by terrestrial industry standards is the "tandem cell" (a cell made by stacking two or more different types of solar cells) combining silicon and perovskite. Taking advantage of the fact that silicon and perovskite absorb different wavelengths of sunlight, the theoretical maximum efficiency reaches 44%. Hanwha Solutions' Q Cells division (Hanwha Qcells), a leader in the domestic solar module industry, is also accelerating R&D on silicon-perovskite tandem cells, targeting commercialization in 2029.
However, in space, it's a different story. Professor Seo explained, "Silicon crystals are hard because they are held together by covalent bonds between atoms, but this makes them heavy to transport and vulnerable to space radiation. Perovskite, on the other hand, forms a flexible crystal structure through ionic bonding, and is known to exhibit characteristics where damaged areas are rearranged or restored even when internal defects occur due to space radiation exposure." He added, "Ultimately, for 'space applications,' perovskite-to-perovskite junctions or perovskite-CIGS (copper-indium-gallium-selenium compound semiconductor) tandem cells are more suitable than silicon-based ones." This is why, alongside the push to mass-produce silicon-perovskite tandem cells for rapid commercialization in areas such as next-generation mobility, technology advancement for space utilization must proceed in parallel.
The remaining challenge is to further enhance resilience to the harsh space environment. Even though radiation durability is relatively strong, the cells must still withstand the powerful impact of rocket launches and the contraction and expansion caused by swings between extreme heat and cold. Professor Seo said, "On the ground, variations are generally assumed to range from about -40°C to 85°C, but space thermal cycles range from below -100°C to above 100°C, making 'thermal shock' far more severe." He added, "Our medium- to long-term goal is to develop additional key technologies to further improve efficiency and stability based on the DJ-structure protective layer."