Ultrafast laser-annealing of perovskite films for efficient perovskite solar cells

Perovskite solar cells have attracted much attention recently for their high efficiency, ease of preparation and low cost. Here, we report a novel laser-annealing method for perovskite films at a low substrate temperature by scanning laser spots on the film surfaces. An ultrafast crystallization process within a few seconds is realized under a laser with a high intensity and a fast scanning speed. Because the crystalline perovskite phase has a stronger light absorption than the amorphous phase, the fast laser annealing can induce a higher temperature in the former and lead to the selective growth of large perovskite grains. Under optimum conditions, perovskite films with high crystallinity are successfully fabricated, resulting in perovskite solar cells with high power conversion efficiency and good stability. Moreover, a faster laser-annealing process of perovskite films is achieved by using a linear laser beam, which is expected to be a promising technique for the mass production of large-scale perovskite solar cells.