Enhanced efficiency and stability of perovskite solar cells by 2D perovskite vapor-assisted interface optimization

Organic–inorganic perovskites solar cells（PSCs） have attracted great attention due to their rapid progress in power conversion efficiency（PCE）. However, there is still an enormous challenge to achieve both high efficiency and stability devices as the decomposition of perovskite materials under humid and light conditions. Herein, we demonstrate that high efficiency and stability of PSCs can be obtained by the reaction of three-dimensional（3D） perovskite with 1, 4-butanediamine iodide（BEAI2） vapor. The incorporation of BEAI2 intensively promotes the crystallization of perovskite film with large grain size（～500 nm）. Further characterization reveals that the post-treatment perovskite film delivered low interface trap density with long carrier lifetime（> 200 ns）, long carrier diffusion length（> 600 nm） and large carrier mobility(> 1.5 cm;V;S;). Solar cells employing such post-treatment films demonstrated 19.58% PCE without hysteresis. Moreover, the post-treatment devices can retain over 90% original efficiencies stored under ambient atmospheric conditions and exhibit better stability under 85 ℃ and continuous illumination as a two-dimensional（2D） perovskite thin layer is formed on the surface/or at the grain boundaries of 3D perovskite. This study offers an effective way to obtain PSCs with high efficiency and stability.