Although perovskites are a promising alternative to silicon for solar cells, new manufacturing processes are needed to make them practical for commercial production. To help fill this gap, researchers at Mahidol University in Thailand 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.
Researchers have come up with a new spray coating method, called sequential spray deposition, and shown 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. In this way, 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 onto another perovskite material that has better electrical properties. This double-layer semi-transparent device showed clearly defined layers and simultaneously achieved high performance and good stability. They 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.