Effect of BPFz on the Performance of Inorganic Perovskite Film and Solar Cells

Inorganic perovskite exhibits an appropriate bandgap and excellent light and thermal stability, making it an ideal top-cell material for silicon tandem solar cells. However, significant non-radiative recombination losses due to surface defects in inorganic perovskite films, along with phase stability issues in humid environments, restrict the efficiency improvement of inverted inorganic perovskite solar cells (IPSCs). This work reports the preparation of efficient, stable inverted IPSCs by using a multifunctional molecule, bis (pentafluorophenyl) zinc (BPFz), as surface treatment for CsPbI_2.85Br_0.15 films. After treatment with BPFz, the inorganic perovskite film undergoes secondary grain growth, significantly increasing grain size. Simultaneously, BPFz can passivate undercoordinated Pb²⁺, effectively suppressing nonradiative recombination. Additionally, the fluorinated phenyl group endows the inorganic perovskite film surface with superhydrophobic properties, protecting the perovskite layer from the influence of environmental humidity, while also helping to suppress ion diffusion within the device, enhancing device stability. Ultimately, after surface treatment with BPFz, the efficiency of inverted IPSCs increases from 18.18 to 20.22%, and V_OC increases from 1.169 to 1.231 V, with excellent moisture and thermal stability. This work provides a new approach for the development of high-efficiency and stable IPSCs in the future.