Recrystallized Perovskite Thin Film via Intense Pulse Light Sintering for Vertical Gradient Band Gap Perovskite Solar Cells

A wet preparation process was developed to prepare vertical gradient perovskite film (MAPbBr₃/MAPbBr_3–xI_x/MAPbI₃) for solar cells. To avoid mutual dissolution, an MAPbBr₃ quantum dot (QD) ink was directly inkjet printed on a spin-coated MAPbI₃ film to create stacked perovskite layers (MAPbBr₃ QD/MAPbI₃). Intense pulse light (IPL) was used to sinter the stacked perovskite films. After the IPL sintering process, the grain size in the stacked layers significantly increased from 16 to 30 nm (MAPbBr₃ QD) and from 123 to 538 nm (MAPbI₃), respectively. Meanwhile, between the stacked layers, a mixed halide perovskite (MAPbBr_3–xI_x) film with a gradient was created. The IPL-sintered perovskite films remained stable without phase separation under 15 W/cm² illimitation for 20 s. The gradient perovskite films were further assembled as an absorber layer in solar cell and exhibited a power conversion efficiency (PCE) of 17.06%. Moreover, the solar cell with vertical gradient showed good moisture stability and exhibited 80% PCE under relative humidity (RH) = 70% for 500 h. In summary, this process can create an interfacial gradient layer between light-absorbing materials and can be further applied to other material systems.