A research group consisting of Yugo Nakahara, a first?year doctoral student in the Graduate School of Natural Science and Technology at Kanazawa University, Associate Professor Md. Shahiduzzaman, and Professor Tetsuya Taima of the Nanomaterials Research Institute has successfully achieved perovskite films fabrication under ambient conditions and improved operational moisture stability in perovskite solar cells (PSCs).
PSCs have attracted considerable attention as a next?generation photovoltaic technology that can be manufactured at low cost using printing processes and may contribute to realizing a decarbonized society. The research group has been working on developing mass?production technologies using the roll?to?roll (R2R) viable method (Figure 1) to address the issues of high weight and high cost associated with conventional silicon solar cells. In particular, to suppress degradation of the perovskite layer caused by moisture, they previously developed a technique to enhance durability by increasing hydrophobicity through the addition of ionic liquids (Reference 1). However, this earlier work employed the spin?coating method (Figure 2), in which small glass substrates are rapidly rotated under a nitrogen atmosphere to form thin films. In contrast, the R2R method requires drying meter?scale films over several minutes under ambient conditions, raising questions about whether the ionic?liquid?based approach could also be effectively applied.
In this study, the group investigated the applicability of the ionic?liquid additive technique under ambient conditions using the bar?coating method (Figure 3), which employs the same film?forming principle as the R2R process. The results showed that, with a drying time of five minutes nearly three orders of magnitude longer than that used in spin?coating-large, micrometer?scale crystals with minimal grain boundaries (*1) were successfully formed. Furthermore, in an atmospheric exposure test (*2), the devices retained more than 90% of their initial performance even after 1,200 hours.
This technology was developed through a collaborative research project with Reiko Co., Ltd. (Headquarters: Kyoto, Japan; President?Director: Junichi Iwai). Based on part of these results, the company is currently conducting a large?scale demonstration test under harsh port?side environmental conditions at the rooftop plaza of the Osanbashi Yokohama International Passenger Terminal, as part of an environmental R&D program supported by the Ministry of the Environment (Figure 6).
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The results of this study were first published online in the online edition of Solar Energy Materials and Solar Cells on November 13, 2025, and were formally published on January 15, 2026.
Figure1. Roll?to?Roll (R2R) Process: Photograph of Reiko Co., Ltd.’s R2R System (Left) and Its Schematic Illustration(Right)
Figure 2. Spin?Coating Method: Photograph of the Spin?Coating System (Left) and Its Schematic Illustration (Right)
Figure 3. Bar-Coating Technique: Photograph of the bar-coating apparatus used in this study (left) and its schematic illustration (right)
Figure 6. Perovskite solar cell module installed at the rooftop plaza of the Osanbashi Yokohama International Passenger Terminal. The module measures 30 cm × 1 m.
【Reference 1】
Kanazawa University Press Release “Enhanced Long-Term Moisture Stability of Perovskite Solar Cells Achieved by Adding Just One Drop of Ionic Liquid.” April 2021.
【Glossary】
*1: Grain boundary
The interface between individual crystalline domains. In this region, the crystal lattice is disrupted, creating defects that can significantly influence electrical and other material properties.
*2: Atmospheric exposure test
A test to examine changes in performance after exposure to a normal atmosphere (40% humidity conditions) containing water and oxygen. In this study, the temperature during exposure was controlled at approximately 25?°C.
Click here to see the press release【Japanese only】
Journal： Solar Energy Materials and Solar Cells
Researcher Information：Md. Shahiduzzaman (Sohel)
Tetsuya Taima
Related Information
Taima-Sohel Laboratory Web site: https://taimalab.wixsite.com/mysite
College of Science and Engineering Web site: https://www.se.kanazawa-u.ac.jp/
Graduate School of Natural Science and Technology Web site: https://www.nst.kanazawa-u.ac.jp/
Nanomaterials Research Institute Web site: https://nanomari.w3.kanazawa-u.ac.jp/
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