Defect passivation with potassium trifluoroborate for efficient spray-coated perovskite solar cells in air

Defects as non-radiative recombination centers hinder the further efficiency improvements of perovskite solar cells (PSCs). Additive engineering has been demonstrated to be an effective method for defect passivation in perovskite films. Here, we employed (4-methoxyphenyl) potassium trifluoroborate (C7H7BF3KO) with BF3- and K+ functional groups to passivate spray-coated (FAPbl(3))(x)(MAPbBr(3))(1-x )perovskite and eliminate hysteresis. It is shown that the F of BF3- can form hydrogen bonds with the H atom in the amino group of MA(+)/FA(+) ions of perovskite, thus reducing the generation of MA(+)/FA(+) vacancies and improving device efficiency. Meanwhile, K+ and reduced MA(+)/FA(+) vacancies can inhibit ion migration, thereby eliminating hysteresis. With the aid of C7H7BF3KO, we obtained hysteresis-free PSCs with the maximum efficiency of 19.5% by spray-coating in air. Our work demonstrates that additive engineering is promising to improve the performance of spray-coated PSCs.

Automated summary

This study demonstrated the use of additive engineering to improve the efficiency of spray-coated perovskite solar cells (PSCs). The (4-methoxyphenyl) potassium trifluoroborate (C7H7BF3KO) was used to passivate the perovskite film and eliminate hysteresis. The results showed that the F in BF3- can form hydrogen bonds with the H atom in the MA(+)/FA(+) ions, reducing the generation of vacancies and improving device efficiency. Additionally, the K+ ions and reduced vacancies can inhibit ion migration, eliminating hysteresis.