- Korea Institute of Energy Research removes lithium ions using nickel oxide catalyst

- World-class durability achieved under high-temperature, high-humidity conditions

Researchers at the Korea Institute of Energy Research conduct performance tests on lithium-ion removal technology. [Korea Institute of Energy Research]
Researchers at the Korea Institute of Energy Research conduct performance tests on lithium-ion removal technology. [Korea Institute of Energy Research]

South Korean researchers have developed a new technology that addresses the longstanding durability problem of perovskite solar cells, a leading next-generation solar technology. The cells retained 95 percent of their initial efficiency after 1,000 hours in extreme conditions of 85 degrees Celsius and 85 percent humidity.

The Korea Institute of Energy Research announced Thursday that a research team led by Senior Researcher Ahn Se-jin of its photovoltaics research division had developed a new manufacturing process that uses a nickel oxide catalyst to remove lithium ions — the key culprit behind shortened cell lifespans.

Perovskite solar cells have drawn attention as a next-generation photovoltaic technology because of their high light-to-electricity conversion efficiency and their ability to be combined with conventional silicon solar cells to maximize power generation. They are particularly valued as a core material in tandem solar cells, which stack a perovskite layer on top of a silicon cell.

Despite their high efficiency, however, vulnerability to heat and moisture has long been cited as the biggest obstacle to commercialization.

The root of the problem lies in the hole transport layer, which helps electricity flow smoothly inside the cell. Conventional manufacturing uses lithium salts and dissolving additives to improve charge-carrier efficiency.

Under high-temperature, high-humidity conditions, those additives evaporate, creating microscopic gaps and defects inside the cell. Lithium ions released from the lithium salts then migrate through the cell's interior, accelerating performance degradation.

To solve this, the research team developed what it calls a "catalytic reaction followed by filtering extraction" process — a method that triggers only the necessary chemical reactions and then removes the substances responsible for lifespan degradation.

The key is a nickel oxide (NiOx) catalyst. When nickel oxide powder is added to the hole transport layer manufacturing solution, the catalyst surface transforms into a state that strongly attracts lithium. This allows lithium ions to be separated from the lithium salts and bound to the nickel oxide surface — without the conventional additives.

The nickel oxide powder, along with the lithium ions attached to it, is then removed by filtration. The process selectively eliminates only the substances that shorten the cell's lifespan while preserving the reactions needed to maintain performance.

A solar cell sample with the lithium-ion removal technology applied. [Korea Institute of Energy Research]
A solar cell sample with the lithium-ion removal technology applied. [Korea Institute of Energy Research]

Perovskite solar cells produced using the new process retained 95 percent of their initial efficiency after 1,000 hours at 85 degrees Celsius and 85 percent relative humidity — a world-class level of durability, the institute said.

The cells also recorded a photoelectric conversion efficiency of 25.24 percent, edging out the 25.21 percent achieved with conventional additive-based processes. The results confirm that lifespan and efficiency can be improved at the same time.

The technology is also significant because it does not require a complete overhaul of existing manufacturing processes — it simply adds a catalytic reaction step and a filtration step. Researchers expect it to contribute to the commercialization of both perovskite-silicon tandem solar cells and thin-film tandem solar cells.

"This research is meaningful because it breaks away from the conventional perovskite manufacturing framework and proposes a new process that uses a catalyst to trigger only the necessary reactions and then filters out the problematic substances," Ahn said. "By resolving the chronic lifespan problem, it will serve as an important milestone in accelerating the commercialization of perovskite and tandem solar cells."

The research, conducted in collaboration with a team led by Professor Kim Dong-seok of UNIST, was published as the cover paper of the May issue of the international journal Advanced Science.


nbgkoo@heraldcorp.com