Enhanced Thermal Stability in Perovskite Solar Cells by Assembling 2D/3D Stacking Structures.

Two-dimensional (2D) perovskites have been shown to be more stable than their three-dimensional (3D) counterparts due to the protection of the organic ligands. Herein a method is introduced to form 2D/3D stacking structures by the reaction of 3D perovskite with n-Butylamine (BA). Different from regular treatment with n-Butylammonium iodide (BAI) where 2D perovskite with various layers form, the reaction of BA with MAPbI only produce (BA)PbI, which has better protection due to more organic ligands in (BA)PbI than the mixture of 2D perovskites. Compared to BAI treatment, BA treatment results in smoother 2D perovskite layer on 3D perovskites with a better coverage. The photovoltaic devices with 2D/3D stacking structures show much improved stability in comparison to their 3D counterparts when subjected to heat stress tests. Moreover, the conversion of defective surface into 2D layers also induces passivation of the 3D perovskites resulting in an enhanced efficiency.