Researchers at Sophia University in Tokyo, led by Professor Yuko Takeoka of the Faculty of Science and Technology's Department of Materials and Life Sciences, together with contributing researchers from the National Institute for Materials Science (NIMS), have developed a multifunctional molecular passivation strategy for tin-based perovskite solar cells that improves both efficiency and long-term durability. Adding a small heteroatom molecule, 2-aminobenzothiazole (2-ABZ), to quasi-two-dimensional Ruddlesden-Popper tin perovskite devices raised power conversion efficiency to 9.07%, up from 6.60% for untreated control devices, while improving how well the cells hold up over time.
Tin-based perovskites are widely seen as the leading lead-free alternative to conventional lead halide perovskite solar cells, offering a route around the toxicity concerns associated with lead, but they have historically lagged behind on both efficiency and stability, limiting their commercial viability. The Sophia University and NIMS team addressed this by incorporating 2-ABZ, a molecule containing nitrogen, carbon, sulfur, and hydrogen, into the perovskite layer as what the researchers describe as a multifunctional molecular stabilizer. Rather than targeting a single failure mode, 2-ABZ acts across the device architecture: it regulates crystallization, reduces trap formation, prevents ion migration, inhibits tin oxidation, and improves interfacial energy alignment.
The additive builds up at the interface and creates densely populated nucleation sites at the base of the perovskite layer, which the researchers found decreases buried defects and produces a higher-quality, more stable film. Beyond the efficiency gain, 2-ABZ-treated devices showed improved open-circuit voltage, stronger photocurrent generation, greater reproducibility, and reduced hysteresis relative to untreated cells. The durability improvement was the most pronounced result: unencapsulated devices with 2-ABZ retained 84.94% of their initial efficiency after 100 days of storage, compared with just 48.95% for untreated control devices, and maintained about 89% of their performance after 10 hours of continuous operation under simulated sunlight, while untreated cells degraded rapidly within the first hour.
"I've been researching perovskite compounds for over 25 years, and I wanted to use that experience to create safer solar cells," said Takeoka. On the passivation mechanism, she added: "The buildup of 2-ABZ at the interface is crucial for decreasing buried defects in the perovskite layer by creating densely populated nucleation sites at the base of the layer, resulting in the production of a high-quality and stable film." She noted that "the findings from our research showed the way for developing safer lead-free solar cells, which could help expand the use of photovoltaic cells."
Takeoka's group is pursuing lightweight, flexible, and shape-controllable perovskite cells for niche applications, and positions the 2-ABZ passivation strategy as a step toward addressing the intrinsic efficiency and stability weaknesses that have limited tin-halide perovskite solar cells relative to their lead-based counterparts.
