Durable and Efficient 2D/3D Perovskite Bulk Heterojunction Solar Cells via BA2MAPb2I7 Single Crystal Addition

The construction of 2D/3D perovskite bulk heterojunctions can combine the stability of 2D perovskites with the favorable charge carrier transport properties of 3D perovskites, thereby enabling efficient and durable perovskite solar cells. However, the controlled manipulation of the n-value and phase purity of the 2D perovskite within the heterojunction often faces significant challenges due to the complex quantum well structure and the chemical environment of the reaction. In this study, we obtained bulk heterojunction films comprising n=3 BA2MA2Pb3I10 2D perovskite and 3D perovskite by adding BA2MAPb2I7 2D perovskite single crystal precursors into a 3D perovskite precursor solution. The introduction of the 2D perovskite enhances the built-in electric field of the perovskite solar cell and passivates film defects, thereby reducing nonradiative recombination and promoting charge carrier transport and collection, leading to significant improvements in VOC, FF, and PCE. Furthermore, both the 2D/3D perovskite films and the corresponding solar cells exhibit substantially improved stability.