Controlling the microstructure and orientation of PbI2 for highly efficient and stable perovskite solar cells

The two-step sequential deposition method has been widely applied to fabricate the perovskite films due to its better reproducibility and easy operation. The perovskite film is formed by a reaction of the pre-deposited PbI 2 film with organic amine salts. Therefore the microstructure and crystal orientation of the pre-deposited PbI 2 are crucial for preparing high-quality perovskite film. However, controlling the growth of the pre-deposited PbI 2 is a challenge. Herein, we added an additive of 1, 4-dichlorobenzene (DCB) to the PbI 2 precursor solution. The DCB molecule connects two crystal planes of the PbI 2 through an interaction between the Pb 2+ and the two Cl − in DCB, which induces the formation of a layered structure PbI 2 , and the growth along with the (001) plane to form an orientated PbI 2 film. Thus high-quality perovskite films with reduced defect states, improved charge transfer efficiency, and better energy level structure were obtained. Consequently, a high efficiency of 24.27% was achieved for the perovskite solar cells (PSCs) with DCB additive. Moreover, the stability of the PSCs was improved. The unencapsulated devices remain 82.6% of the initial efficiency after aging for 1100 h in air.