Overcoming the wetting issues of PTAA in inverted perovskite solar cells by cinnamyl alcohol modification

The hydrophobic nature of poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)(PTAA) limited the performance, stability as well as reproducibility of the inverted perovskite solar cells (PSCs). Herein, an efficient interface modification strategy based on cinnamyl alcohol (CA) has been proposed to solve these challenges. As a result, the wettability of the perovskite on the surface of the PTAA film is significantly improved, which correspondingly enhances the film quality of the perovskite layer and the interface contact with the PTAA layer. At the same time, the trap states as well as interface energy loss are greatly eliminated, and promotes the improvement of device performance, stability and reproducibility. The short-circuited and abnormal devices have been eliminated, and repeatability of devices are dramatically improved with CA treatment. The average power conversion efficiency (PCE) of the device increased by 75.20%, rising from 10.22% to 19.41%, while the highest PCE achieved with this strategy reached 21.31%. Furthermore, the stability of devices has been greatly improved. This strategy offers a simple yet effective solution for modifying the hydrophobic hole-transport layer in inverted perovskite solar cells to address wettability mismatch, while also providing insights for the selection and design of modifying molecules.