A new hole transfer materials (HTMs) has been developed that solves the problem of moisture vulnerability, which was an obstacle to commercialization of perovskite solar cells (PSCs). The cell using this material has recorded the highest efficiency (24.82%) among perovskite solar cells reported in the papers so far. The ground breaking research result that achieves moisture stability and efficiency at the same time was published online in Science, a world-top scientific journal on September 25. This research is expected to greatly accelerate the commercialization of PSCs.

The joint research team of Korea Institute of Energy Research (President Kim Jong-nam) and UNIST (President Lee Yong-hoon) developed a “fluorine substituted hole transfer materials” that increases cell efficiency while preventing the photoactive layer of PSCs from being exposed to moisture. The new HTMs is a solar cell constituent layer that carries holes (positively charged particles) that is made by the photoactive layer after receiving light. The joint researchers developed new HTMs by simply adding (substituting) fluorine to the existing organic layer material.

Usually when the perovskite is exposed to moisture, the solar cell performance decreases with time. However, the developed new HTMs have a strong hydrophobicity that does not mix with water like how oil does, so the photoactive layer is not easily exposed to moisture. The developed new HTMs also have good performance of hole’s transporting ability.

Dr. Kim Dong-Suk of the Korea Institute of Energy Research, who was in charge of cell fabrication, said, "we obtained an open-circuit voltage (Voc) of above 1.18V, which is close to the theoretical value with a voltage loss of 0.3V (based on 1.48eV of band gap with formamidinium leda iodide PSCs), the lowest value among voltage losses reported so far. "Even if it is manufactured in a large area (1cm2), the reduction in efficiency (22.31%) is small, so the possibility of commercialization becomes brighter.”