Spray Coating Stabilizes Solar Cells

Although perovskites are a promising alter­native to the silicon used to make most of today’s solar cells, new manu­facturing processes are needed to make them practical for commer­cial production. To help fill this gap, researchers have developed a new precision spray-coating method that enables more complex perovs­kite solar cell designs and could be scaled up for mass pro­duction. Perovskites are promising for next-gene­ration solar cells because they absorb light and convert it to energy with better efficiency and poten­tially lower production costs than silicon. Perovskites can even be sprayed onto glass to create energy-producing windows.

Illustration of a sequential spray deposition that enables multilayer perovskite absorber for advanced solar cell designs and could be scaled up for mass production. The technique could be used to create perovskite architectures with any number of layers. (Source: P. Kanjanaboos, Mahidol U.)

“Our work demons­trates a process to deposit perovskite layer by layer with control­lable thick­nesses and rates of deposition for each layer,” said research team leader Pongsakorn Kanjanaboos from the School of Materials Science and Innovation, Faculty of Science, Mahidol University in Thailand. “This new method enables stacked designs for solar cells with better performance and stability.” Now, Kanjana­boos and colleagues describe their new spray coating method, called sequen­tial spray depo­sition, and show that it can be used to create a multi­layer perovskite design. Applying different perovskite materials in each layer can allow customi­zation of a device’s function or the ability to meet specific performance and stabi­lity require­ments.

One of the advantages of perovskites are that they are solution proces­sable, meaning that a solar cell is made by drying liquid perovskite into a solid at a low temperature. This fabri­cation process is much easier and less expensive than making a traditional silicon solar cell, a process that requires very high tempera­tures and cutting a solid material into wafers. However, the solution process typically used to make perovs­kites does not allow multilayer designs because the upper layer tends to dissolve the already-dried lower layer. To overcome this challenge, the researchers turned to a process known as sequential spray deposition in which tiny droplets of a material are applied to a surface.

After trying different spray coating methods, they found one that worked at tempera­tures around 100 °C. They then optimized the spray parameters to ensure that the tiny droplets dried and crystalized into solid perovskite immediately upon contact with the already-dried lower layer. “With our spray coating process, the solution of the upper layer doesn’t disturb the solid film making up the first layer,” said Pongsa­korn. “Endless combi­nations of stacked perovskite archi­tectures with any number of layers can be designed and created with precise control of thicknesses and rates of deposition for each layer.”

The researchers demons­trated the technique by depositing a perovskite material with high stabi­lity on different perovs­kite material with better electrical properties. This double-layer semi-trans­parent perovskite device showed clearly defined layers and simul­taneously achieved high performance and good stabi­lity. The researchers plan to use the new approach to make multi­layer perovskite devices with new functions and combinations of perfor­mance and stability that were not possible before. (Source: OSA)

Reference: K. Amratisha et al.: Layer-by-layer spray coating of a stacked perovskite absorber for perovskite solar cells with better performance and stability under a humid environment, Opt. Mat. Exp. 10, 1497 (2020); DOI: 10.1364/OME.391546

Link: School of Materials Science and Innovation, Faculty of Science, Mahidol University, Bangkok, Thailand

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