Researchers in China have developed a technique that could allow cost effective scaling up of production of large area solar panels using perovskite materials.
Perovskite solar cells have potential with high conversion efficiency and low production cost, but it has been difficult to scale up from small-size laboratory devices to large-scale modules or panels needed for commercial use.
The research team in Hong Kong has demonstrated that a self-assembled monolayer can help the formation of a large-area perovskite film using a blade-coating process. They believe this new process, detailed in a paper in Nano Research Energy, will enable the commercialization of the perovskite solar cell technology.
Compared to silicon solar cells, those built with perovskite materials can be manufactured at a great savings of cost and energy. Additionally, perovskite solar cells are lightweight and versatile enough to be used in places like windows and contoured roofs. The world record efficiency of the perovskite solar cells is as high as 25.7 percent, which rivals the efficiency of the silicon solar cells.
Researchers built solar cells with layers of material deposited on an underlying substrate. In adapting the high-speed blade-coating method for perovskite thin-film deposition, the researchers realized that the surface properties of the substrate are critical for large-area coating and perovskite growth. The current process leaves voids at the buried interface of the perovskite film that hits the device performance.
“To solve this problem, we have screened various hole-transporting materials and found that self-assembled monolayers are a class of promising materials for the upscaling of perovskite devices,” said Alex Jen, a professor at City University of Hong Kong.
The self-assembled monolayers contain an anchoring group that can bond to the substrate and a functional headgroup to passivate the defects for the perovskite on top. These self-assembled monolayer molecules function as linkers, to bond the substrate and perovskite films tightly to eliminate interfacial voids.
“Furthermore, since the self-assembled monolayer is a monolayer, charge carriers can be extracted from perovskite to substrate electrode efficiently through charge tunneling, resulting in enhanced device performance,” said Jen.
These functional self-assembled monolayers, that can be solution-processed, are very economical because of the minimal materials required. The self-assembled monolayers prove to be very effective for tuning the perovskite growth and passivating any potential defects. “This novel class of materials is very promising for facilitating the upscaling of perovskite photovoltaic technology,” said Jen.
The researchers plan to test different self-assembled monolayer molecules designed for upscaling the perovskite photovoltaic technology and conduct composition engineering of perovskite precursors for upscaling coating methods. The interaction between perovskite and self-assembled monolayers is critical.
In order to achieve highly efficient and stable photovoltaic modules, the coating of perovskites has to be uniform and free of defects. “We believe our research will help reduce the lab-to-fab gap to facilitate the commercialization of perovskite photovoltaic technology,” said Jen.
The research team includes Jie Zeng, Leyu Bi, Yuanhang Cheng, and Alex K.-Y. Jen from the City University of Hong Kong; and Baomin Xu from the Southern University of Science and Technology, Shenzhen, China.
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