By Do-yi Lim
Health Korea News

SEOUL, South Korea, July 21 — South Korean researchers have developed a perovskite solar cell that can withstand direct exposure to water by reinforcing the material's interface with a molecular network inspired by the structure of a fishing net.

The technology addresses one of the biggest barriers to the commercialization of perovskite solar cells: their vulnerability to moisture and oxygen. Perovskite cells can deliver power-conversion efficiencies comparable to those of conventional silicon solar cells while potentially allowing lower-cost and lower-temperature manufacturing.

Their performance, however, can deteriorate rapidly when exposed to rain, humidity or oxygen. Researchers have generally relied on external encapsulation layers to protect the devices, but these layers can increase manufacturing complexity and cost while reducing the flexibility and low weight that make perovskite cells attractive.

A research team led by So-Yeon Kim and Dong-Chan Lim at the Korea Institute of Materials Science, or KIMS, developed a tightly connected molecular layer at the perovskite interface using copper ions, bathocuproine and polyethylenimine ethoxylated.

Copper ions, or Cu²⁺, served as connecting nodes in the network. Bathocuproine, or BCP, formed a rigid barrier against moisture, while the flexible polymer PEIE linked the molecular components and acted as an adhesive and buffer.

The resulting structure resembled a densely woven fishing net. It blocked water from penetrating the device while suppressing ion migration, another major cause of performance degradation in perovskite solar cells.

Unlike conventional strategies that depend primarily on thick external protection, the researchers sought to give the solar-cell material and its interfaces intrinsic resistance to moisture.

The interfacial design also reduced defects, improved charge extraction and suppressed the diffusion of silver from the electrode into the device, which can contribute to structural damage and long-term performance loss.

The team fabricated the solar cells under ambient-air conditions without using a glovebox, a sealed system normally used to exclude moisture and oxygen during perovskite-cell production.

The cells achieved certified power-conversion efficiencies of 26.19% at a bandgap of 1.53 electron volts, 24.11% at 1.61 eV and 20% at 1.77 eV.

The results indicate that the interfacial network can be applied across several perovskite compositions rather than being limited to a single material formulation. This versatility could support the development of perovskite-silicon tandem solar cells, which combine materials with different bandgaps to capture a broader range of sunlight.

The researchers also immersed unencapsulated devices directly in water, subjecting them to more severe conditions than conventional high-humidity testing.

Devices incorporating the fishing-net-inspired interface retained or recovered their performance after repeated water-immersion tests, according to the research team.

Flexible devices using the same technology also maintained a high proportion of their performance after more than 10,000 bending cycles, suggesting potential applications in lightweight and bendable solar-energy systems.

"The main distinction of this study is that we made the solar-cell material itself more resistant to water," Kim and Lim said. "We plan to apply the technology to mass-production processes and silicon-perovskite tandem solar cells, with the aim of accelerating commercialization in areas such as building-integrated and agricultural photovoltaics."

Perovskite solar cells can be manufactured through relatively low-temperature solution processes. Their thin and lightweight structures could support building-integrated photovoltaics, vehicle-integrated photovoltaics, wearable devices and self-powered Internet of Things sensors.

Improved water resistance could also expand their use in humid or wet environments, including smart agriculture, aquaculture monitoring, outdoor sensing systems and portable power supplies.

The researchers plan to extend the work to large-area modules, roll-to-roll manufacturing and long-term outdoor reliability testing.

The study, titled "Air-processed and water-stable perovskite solar cells enabled by a fishing-net-inspired interfacial network," was published July 17 in Nano-Micro Letters.

Muh Fadhil Albab of KIMS was the first author. So-Yeon Kim and Dong-Chan Lim served as corresponding authors.

The research was supported by the Ministry of Science and ICT, the National Research Foundation of Korea's Pioneer Program for Converging Technology and KIMS' institutional research program.