Perovskite materials are becoming increasingly popular as an active layer in solar cells. Internal forces in these materials cause distortions in their crystal structures, reduce symmetry, and contribute to their intrinsic instability. They are also subject to environmental damage.
Researchers at Soochow University examined the mechanisms that play a role due to this intrinsic instability, as well as various degradation factors that influence the performance of perovskite photovoltaics. In a research update published by AIP Publishing in APL Materials, the researchers clarified the factors influencing degradation and summarized some possible approaches for permanent perovskite photovoltaics.
“Understanding the mechanisms of degradation under various conditions, including light, heat, humidity, electrochemical environment, and inherent stability, is important if you are to improve the durability of perovskite solar cells,” said author Zhao-Kui Wang. “It is important to make sure that the perovskite and the other layers have the best inherent stability and then make some adjustments to further improve the environmental durability.”
The update focused on the chemical degradation caused by the transport layers in solar cells. The inherent stability of the perovskite layer and the environmental factors moisture, oxygen, light and heat were also taken into account.
The authors indicated that compositional engineering and bond passivation, which reduce tiny gaps in these materials, are promising methods associated with doping, modifying, and adjusting the perovskite films and device durability.
The authors also highlighted the advantages of hydrophobic materials, wide band gap materials, and ionic liquids in optimizing photovoltaic durability under different environmental conditions. For example, they suggested making a 2D-3D heterostructure out of the perovskite material to improve its air stability.
The authors note that ionic liquids show promise because of their ability to suppress ion migration, which is important to ensure thermal stability and retard light-induced degradation. Such ionic liquids can be easily modified to have hydrophobicity for moisture filtration.
“Because of their low volatility, ionic liquids can be considered an environmentally friendly solvent for perovskites, but the efficiency of the device still needs to be improved,” said Wang.
The authors encourage others to continue to search for materials with specific energy conduction areas known as wide band gap materials that increase stability in perovskite photovoltaics.
“We proposed the concepts of pure oxygen stability and flexible stability, which are valuable for other researchers to pay attention to,” Wang said. “Furthermore, we hope that these strategies will be useful not only in perovskite solar cells, but also in other photoelectric systems such as organic photovoltaics, photodetectors and light emitting diodes.”
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