In a significant advancement in solar energy technology, a team of researchers at City University of Hong Kong (CityUHK) has developed a groundbreaking living passivator that substantially enhances the stability and efficiency of perovskite solar cells.

Led by Professor Feng Shien-ping, Associate Dean in the College of Engineering and Professor in the Department of Systems Engineering at CityUHK, this innovative coating mimics sustained-release capsules in drugs, which continuously release chemicals to heal defects caused by environmental stressors like water and heat, making it a promising solution for next-generation perovskite photovoltaics.

In collaboration with Professor Henry J. Snaith at the University of Oxford and Professor Angus Yip Hin-lap, Associate Director of the Hong Kong Institute for Clean Energy at CityUHK, the research paper, titled “Water- and heat-activated dynamic passivation for perovskite photovoltaics”, was recently published in the prestigious scientific journal Nature.

Perovskite solar cells are known for their impressive ability to convert sunlight into electricity, making them a strong contender for the next generation of solar panels. However, they have faced challenges in becoming widely used due to concerns about their long-term storage and operational stability. Various passivation strategies have been developed to improve their performance and reliability, but there is difficulty addressing new defects caused by exposure to water and heat over time during operation.

To overcome these challenges, the team has developed new "living" passivators using a special material. The newly developed passivator leverages dynamic covalent bonds that activate upon exposure to moisture and heat, enabling it to evolve new passivators in response to environmental factors. This innovative approach allows for real-time repair and maintenance of perovskite solar cells.

Extensive experiments demonstrated that the passivator significantly improves the performance and durability of perovskite solar cells. This new passivation strategy has achieved a photovoltaic conversion efficiency of over 25% and maintained operational stability for more than 1,000 hours at high temperatures and in humid conditions.

“Applying a living passivator on the perovskite surfaces enhances their resistance to environmental factors like moisture and heat. This improves the stability of perovskite solar cells in hot and humid conditions, introducing a dynamic, responsive approach to environmental stressors,” explained Dr Wang Weiting, the first author of this study and a Research Associate on Professor Feng's team.

“Consider the resilience of plants and other living beings to various weather conditions, while perovskite solar cells deteriorate within months. The key difference lies in the ability of living organisms to regenerate and heal evolving defects. By incorporating a passivation mechanism that dynamically heals during operation, we can potentially unlock this regenerative concept for perovskite or other electronic devices,” said Professor Feng.

The team is currently collaborating with industry partners to apply this technology to address issues related to ionic migration and instability in perovskite solar cells during both the manufacturing and operation stages. Making them more stable and reliable could help make these solar cells more commercially viable. This technology could be used in other applications, such as anti-oxidation and interfacial contact engineering in microelectronic devices.

Professor Feng and Professor Henry J. Snaith are the corresponding authors of the paper.