Perovskite solar cell are an interesting alternative. They can be printed with inks and are low-cost, lightweight, efficient, flexible, and thin. However, they are less efficient than silicon solar cells and more importantly, have a lower stability rate, which can cause them to fail in normal environmental conditions.
These problems may be solved by new metal-containing materials, called ferrocenes. City University of Hong Kong (CityU), has added Imperial-made Ferrocenes to perovskite solar cell, greatly improving their efficiency. These results were published in the journal Science today, April 21, 2022.
Professor Nicholas Long from Imperial’s Department of Chemistry was co-lead author. He stated: “Silicon cell efficiency is expensive and we urgently require new solar energy devices to accelerate our transition to renewable energy. Stable, efficient perovskite cell could eventually allow solar energy to serve more purposes, from powering the developing countries to charging new generations of wearable devices.
“Our collaboration with Hong Kong colleagues was wonderfully serendipitous. It began after I gave a talk on new ferrocene compound and Dr. Zonglong Zhu, from CityU, asked me to send some samples. The CityU team informed us within a few months that the results were very exciting and asked us to send them more samples. This began a research program that resulted in perovskite products that are more efficient and stable.
Ferrocenes have the power to change the world
Perovskite is the light-harvesting layer in solar cell devices. These devices are not as efficient in converting solar energy to electricity as silicon-based solar cell. This is due to the fact that the electrons are less mobile – they can’t move between the harvesting layer and the electricity conversion layers.
Ferrocenes are compounds that have iron in the center and are surrounded by carbon sandwiching rings. Professor Geoffrey Wilkinson, an Imperial Nobel Prize-winner, first identified the unique structure of ferrocene in 1952. Today, ferrocenes remain a subject of intense research around the globe for their unique properties.
Their structure is known for its excellent electron richness. This allows electrons to move more easily between the layers of perovskite and the subsequent layers. This improves the efficiency of converting sunlight into electricity.
The efficiency of perovskite devices with an additional ferrocene layer, according to tests by CityU and commercial labs, can exceed 25%. This is comparable to traditional silicon cells.
You can kill two birds with one stone
This is not the only problem that ferrocene-based materials have solved. Imperial’s team experimented with different chemical groups attached to carbon rings of ferrrocene. After sending several versions to Stephanie Sheppard (a PhD student), the collaborators found a version that greatly improves attachment of the perovskite to the rest.
The added attachment power increased the device’s stability, allowing them to maintain more than 98% efficiency after operating continuously at maximum power for 1,500hours. These perovskite devices are now close to traditional silicon cell standards due to their increased efficiency and stability.
CityU’s lead researcher, Dr. Zonglong Zhu, said that the team has patent their design and plans to license it to bring their perovskite products to the market. They are currently experimenting with other ferrocene designs in order to improve performance and stability.