Carbon Dots from Human Hair Boost Solar Cells

In a study published in the Journal of Materials Chemistry A, the researchers led by Professor Hongxia Wang in collaboration with Associate Professor  Prashant Sonar  of the Queensland University of technology  (QUT) in Australia  showed the carbon nanodots could be used to improve the performance of perovskites solar cells, a relatively new photovoltaic technology, are seen as the best PV candidate to deliver low-cost, highly efficient solar electricity in coming years. They have proven to be as effective in power conversion efficiency as the current commercially available monocrystalline silicon solar cells, but the hurdles for researchers in this area is to make the technology cheaper and more stable. Unlike silicon cells, they are created with a compound that is easily manufactured, and as they are flexible they could be used in scenarios such as solar-powered clothing, backpacks that charge your devices on the go and even tents that could serve as standalone power sources.

This is the second major piece of research to come as a result of a human hair derived carbon dots as multifunctional material. Last year, Associate Professor Prashant Sonar led a research team, including Centre for Materials Science research fellow Amandeep Singh Pannu, that turned hair scraps into carbon nanodots by breaking down the hairs and then burning them at 240 degrees celsius. In that study, the researchers showed the carbon dots could be turned into flexible displays that could be used in future smart devices.

In this new study, Professor Wang’s research team, including Dr Ngoc Duy Pham,  and Mr Pannu, working with Professor Prashant Sonar’s group, used the carbon nanodots on perovskite solar cells out of curiosity. Professor Wang’s team had previously found that nanostructured carbon materials could be used to improve a cell’s performance. After adding a solution of carbon dots into the process of making the perovskites, Professor Wang’s team found the carbon dots forming a wave-like perovskite layer where the perovskite crystals are surrounded by the carbon dots.

It creates a kind of protective layer, a kind of armour,” Professor Wang said. “It protects the perovskite material from moisture or other environmental factors, which can cause damage to the materials.”

The study found that perovskite solar cells covered with the carbon dots had a higher power conversion efficiency and a greater stability than perovskite cells without the carbon dots.


Mass Production of Low-Cost Solar Cells

An international team of university researchers today reports solving a major fabrication challenge for perovskite cells — the intriguing potential challengers to silicon-based solar cells.

These crystalline structures show great promise because they can absorb almost all wavelengths of light. Perovskite solar cells are already commercialized on a small scale, but recent vast improvements in their power conversion efficiency (PCE) are driving interest in using them as low-cost alternatives for solar panels.

In the cover article published online in Nanoscale, a publication of the Royal Society of Chemistry, the research team reveals a new scalable means of applying a critical component to perovskite cells to solve some major fabrication challenges. The researchers were able to apply the critical electron transport layer (ETL) in perovskite photovoltaic cells in a new way — spray coating — to imbue the ETL with superior conductivity and a strong interface with its neighbor, the perovskite layer.

The researchers turned to spray coating, which applies the ETL uniformly across a large area and is suitable for manufacturing large solar panels. They reported a 30 percent efficiency gain over other ETLs – from a PCE of 13 percent to over 17 percent – and fewer defects.

Added Taylor, “Our approach is concise, highly reproducible, and scalable. It suggests that spray coating the PCBM ETL could have broad appeal toward improving the efficiency baseline of perovskite solar cells and providing an ideal platform for record-breaking p-i-n perovskite solar cells in the near future.”

The research is led by André D. Taylor, an associate professor in the NYU Tandon School of Engineering’s Chemical and Biomolecular Engineering Department, with Yifan Zheng, the first author on the paper and a Peking University researcher. Co-authors are from the University of Electronic Science and Technology of China, Yale University, and Johns Hopkins University.