π-Interactions suppression of buried interface defects for efficient and stable inverted perovskite solar cells

Poly(triarylamine) (PTAA) is commonly utilized as a hole transport layer due to suitable band alignment with perovskite layer, but its poor infiltration of perovskite precursors easily leads to buried interface defects. Here, we propose a molecular bridging strategy to bridge PTAA and perovskite layer by employing the special π-interactions molecule of 2, 4, 6-tris(4-aminophenyl)-s-triazine (TAPT). The amidogen of TAPT can produce H-π bond with the benzene ring in PTAA to make them bind tightly, thus fixing the fractures and reducing defect sites in PTAA, while the triazine ring of TAPT can interact with uncoordinated Pb2+ to form π-Pb2+ bond and passivate Pb2+ defects. In addition, the TAPT assists in achieving a pinhole-free buried interface, which enhances interfacial carrier transport and suppresses interfacial nonradiative recombination. Eventually, the device with TAPT achieves the champion efficiency of 24.57%. The devices with TAPT have greatly improved operating and thermal stability, sustaining 89.7% of the initial efficiency after 1500 hours of maximum power point tracking and 91.9% of the initial efficiency after 1065 hours of 85 oC heat treatment. This approach focuses on the important role of the π-interactions at the buried interface to develop efficient and stable perovskite solar cells.