Bifunctional trifluorophenylacetic acid additive for stable and highly efficient flexible perovskite solar cell

The defects within perovskite films are the fatal roadblock limiting the performance of perovskite solar cells (PSCs). Herein, we develop a patching strategy to obtain high-quality perovskite film using bifunctional trifluorophenylacetic acid (TFPA). Theoretical calculation and experiments reveal that the -COOH groups in TFPA effectively passivate the deep-energy-level defects of perovskite by combining with Pb clusters on the perovskite grain surfaces to enhance the efficiency of PSCs, and hydrophobic benzene groups containing fluorine in TFPA are exposed to improve the stability of PSCs. The power conversion efficiency (PCE) of PSCs with TFPA is enhanced from 22.95% to 24.56%. Most importantly, we successfully fabricated flexible PSCs using TFPA with the high PCE of 22.65%. The devices with TFPA maintain 93.22% of the initial efficiency MPP under continuous irradiation for 10.5 h, while the devices without TFPA only retain 82.22% of the initial efficiency under the same conditions for just 5 h. Meanwhile, the unsealed devices with TFPA hold 93.59% of the initial efficiency when stored in air for 3912 h.

Automated summary

A patching strategy using bifunctional trifluorophenylacetic acid (TFPA) was developed to improve the quality and stability of perovskite films, enhancing the efficiency of perovskite solar cells (PSCs). The power conversion efficiency (PCE) of PSCs with TFPA increased from 22.95% to 24.56%, and flexible PSCs with a high PCE of 22.65% were successfully fabricated. The devices with TFPA showed better long-term efficiency retention under continuous irradiation and storage in air.