Solar cells made from materials known as “perovskites” are catching up with the efficiency of traditional silicon-based solar cells. At the same time, they have advantages of low cost and short energy recovery time. However, these solar cells have stability problems, which Linköping University researchers, together with international collaborators, have now managed to solve. The results, published in Science, are a major step forward in the search for next-generation solar cells.“Our results open up new possibilities for developing efficient and stable solar cells. They also provide new insights into how doping organic semiconductors works.” says Feng Gao, professor at Linköping University’s Department of Physics, Chemistry and Biology (IFM).Perovskites are crystalline materials with great potential to help solve the world’s energy shortage. They are cheap to manufacture, high efficiency and low weight. However, perovskite solar cells can degrade quickly, and it has not been possible to build high-efficiency perovskite-based solar cells with the required stability.“There seems to be a trade-off between high efficiency and stability in perovskite-based solar cells. High-efficiency perovskite solar cells tend to show low stability, and vice versa.” says Tiankai Zhang, a postdoc at IFM and one of the lead authors of the paper published in Science. For more information, see the IDTechEx report on Perovskite Photovoltaics 2023-2033
When solar energy is converted to electricity in perovskite-based solar cells, one or more charge transport layers are usually required. These are located directly next to the perovskite layer in the solar cell. Organic charge transport layers often need helper molecules to function as intended. The material is described as “doped”. A doped transport layer called Spiro-OMeTAD is a benchmark in perovskite solar cells and offers record power conversion efficiencies. But the current method used to dope Spiro-OMeTAD is slow and causes the stability problem of perovskite solar cells.
“We have now managed to remove the compromise that has hindered development, using a new doping strategy for Spiro-OMeTAD. This allows us to obtain high efficiency and good stability,” he added. says Tiankai Zhang.
Another lead author of the paper, Feng Wang, is a junior professor at IFM. He points out that perovskite-based solar cells can be used in many ways and have many areas of application.
“One of the advantages of using perovskites is that the solar cells made are thin, which means they are light and flexible. They can also be semi-transparent. It would be possible, for example, to apply perovskite-based solar cells to large windows . , or building facades. Silicon-based solar cells are too heavy to be used in this way.” says Feng Wang.