A Synergistic Precursor Regulation Strategy for Scalable Fabrication of Perovskite Solar Cells

The nucleation and crystallization processes within solution-processed deposition is key for obtaining perovskite films with high quality. Herein, the synergistic effect of Cs+, ligand solvent (tetramethylene sulfoxide, TMSO), and methylammonium ions (MA(+)) on nucleation and crystallization procedures of preparing perovskites films is studied. The results reveal that producing alpha-phase nuclei in the intermediate-phase film (a perovskite film formed by removing the solvent before annealing) is the key factor for obtaining alpha-phase-pure perovskites, wherein Cs+ is necessary for reducing the formation energy of the alpha-phase. In addition, the nonvolatile ligand (TMSO) is used to inhibit rapid nucleation, because it can form a stable intermediate phase. Furthermore, the introduction of the volatile MA(+) cations compound (MACl) combined with Cs+ contributed to the direct formation of alpha-phase nuclei in the intermediate-phase film, and ion exchange (between FA(+) and MA(+)) occurs during the subsequent annealing process, which leads to the formation of large-grain perovskite film with good crystallinity. Maximum power conversion efficiencies of 22.08% and 16.88% are obtained via this strategy for a perovskite solar cell on a small area (active area: 0.09 cm(2)) and a perovskite solar module (aperture area: 12.92 cm(2)), respectively.