Improved polymer additive enhances perovskite solar cells

Improved polymer additive enhances perovskite solar cells
by Simon Mansfield
Sydney, Australia (SPX) May 16, 2024

Perovskite solar cells, known for their lightweight and flexible nature, are inexpensive and easy to manufacture. They are seen as a promising technology that can be attached to various surfaces. However, these solar cells currently lack durability and efficiency. New research highlights how adding a polymerized ionic liquid to the metal halide perovskite material can improve their performance, potentially facilitating wider adoption of perovskite solar cells.

"The commonly employed solution processing method for fabricating perovskite layers introduces many defects in both the bulk and surface of the perovskite layer. These intrinsic defects within the perovskite absorption layer pose a significant constraint on the overall performance of the devices. Additive engineering has been demonstrated to be effective as a strategy for defect passivation and performance enhancement in perovskite solar cells," said Qi Cao, a researcher at Northwestern Polytechnical University in Xi'an, China.

Researchers are enhancing the properties of ionic liquids by creating polymerized versions. In this study, they synthesized a poly ionic liquid called poly4-styrenesulfonyl(trifluoremethylsulfonyl)imidepyridine (PSTSIPPyri).

The addition of PSTSIPPyri to the perovskite solar cell helps prevent halide ion migration, maintains the crystal structure, and improves the solar cell's stability by fixing organic and halide ions.

"To date, researchers have devoted considerable attention to the meticulous selection of additives that enhance the performance of perovskite solar cells. Among these, ionic liquids have received widespread attention. Ionic bonds in ionic liquids tend to be stronger and more stable, and they offer various tunable properties, including viscosity, polarity, and conductivity," said Xuanhua Li, a researcher at Northwestern Polytechnical University. "This tunability makes it possible to fine-tune the ionic liquid properties to meet the specific requirements of the perovskite film, thereby optimizing device performance."

Testing of the PSTSIPPyri additive involved aging perovskite films for 300 hours at 85C and 60% relative humidity. The enhanced perovskite film showed a slower rate of change than the control film. It also retained 84.5% of its efficiency after 1000 hours in a high humidity, high heat environment, compared to 43.6% for the control.

Long-term durability tests showed that with PSTSIPPyri, the perovskite solar cell maintained 87.6% of its power conversion efficiency after 1,500 hours of continuous light, while the control only maintained 61.1%.

"Incorporating PSTSIPPyri as an additive leads to a significant enhancement in the power conversion efficiency of inverted perovskite solar cells from 22.06% to 24.62%. They also demonstrate excellent long-term operational stability," said Cao. "This strategy illustrates the potential of poly ionic liquids as a promising additive for perovskite solar cells, offering both high performance and stability."

Other contributors include Xingyuan Chen, Tong Wang, Jiabao Yang, Xingyu Pu, Hui Chen, Bingxiu Xue, and Jianbo Yin at Northwestern Polytechnical University in Xi'an, China; Long Jiang at the CNPC Tubular Goods Research Institute in Xi'an, China.

Research Report:Efficiency enhancement to 24.62% in inverted perovskite solar cells through poly (ionic liquid) bulk modification