Solvent evaporation induced preferential crystal orientation BiI3 films for the high efficiency MA3Bi2I9 perovskite solar cells

In this paper, we develop a solvent evaporation induced method and demonstrate that it is effective in suppressing the growth of the BiI3 (003) crystal plane and favoring the growth of BiI3 (113) and (300) crystal planes. By using the as-prepared BiI3 films, we successfully fabricated BiI3 and MA3Bi2I9 (MBI) coexisting films with weakened (006) crystal planes, which are generally oriented parallel to the substrate and prohibit carrier transport. Additionally, compared with MBI films prepared from controlled BiI3 films, the resultant BiI3-MBI film is more suitable for fabricating efficient and stable photovoltaic devices. The best performing photovoltaic device exhibits a power conversion efficiency of 1.53%. This work provides a new strategy for realizing high-efficiency Bi-based perovskite solar cells.