High-quality MAPbI3 film prepared by drip-pressing method in the air for perovskite solar cells

Perovskite solar cells are generally fabricated by one-step or two-step solution deposition in an inert atmosphere . It is obvious that large-scale perovskite film preparation process in the air is the future trend. However, perovskite materials are easily degraded by water, resulting in low nucleation density and incomplete coverage of perovskite film. Here, we choose the drip-pressing method to regulate the quantity of moisture, which can also balance the grains growth and solvent volatility. The perovskite films were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), UV–visible absorption, steady-state photoluminescence (PL) and in situ PL measurement. The orientation and quality of perovskite crystal are improved significantly in drip pressing, compared with traditional spin-coating. In addition, it facilitates to adjust the crystallization kinetics of perovskite by altering the imposed pressure in drip pressing. The grain size increases first and then decreases as pressure increases, reaching a maximum at 10 kPa. Meanwhile, the films become more and more compact as pressure increases. Perovskite films show great photoelectric performance at 30 kPa. The photoelectric conversion efficiency of the device in air can be improved from 10.99% to 13.21%. The results indicate that the drip-pressing method is in favor of high-quality of perovskite crystal in air.