Regulation of phase arrangement in 2D ruddlesden-popper perovskite films via anti-solvent method for efficient solar cells

Recently, quasi-two-dimensional RP(Ruddlesden-Popper)-based perovskite solar cells have attracted a wide range of research interest. However, two-dimensional layered perovskites have disordered phase distribution and multi-quantum well structure that are adversely to charge transport and extraction, resulting in the inability to obtain relatively satisfactory photoelectric conversion efficiency (PCE). Here, we fabricated an 2D RP perovskite solar cell with reversely graded phase arrangement by friendly antisolvent method, and obtained the PCE of 14.45%. The dependence of efficiency on device architecture according to the vertical growth direction is further revealed and discussed. To investigate the effect of different antisolvents on crystal orientation and phase arrangement of GA-based 2D RP perovskites, we applied IPA as antisolvent and found that IPA not only significantly improved the surface roughness, quality and crystallinity of 2D perovskites but also reduce or even eliminate lower-n (n = 1, 2) phases and improve the vertical orientation of 2D phases in perovskites films, thereby improving charge transport and extraction. In the end, we achieved a champion PCE of 15.80%. These findings provide an effective guidance for developing GA-based organic spacers toward highly efficient and stable 2D PSCs with less quantum confinement.