Employment of Multifunctional Small Molecules in Buried Interfaces for Highly Efficient Perovskite Solar Cells

Carbazole-based self-assembled monolayers (SAMs) as hole transport layers (HTLs) have driven significant progress in inverted perovskite solar cells (PSCs). However, the uneven distribution of SAMs and their loose interface contacts with perovskite layers result in severe interface defects and poor film quality of perovskites. Currently, existing strategies alleviate partial issues of interfaces but fail to simultaneously balance the efficiency and stability of devices. Therefore, in this work, we propose a new molecule, 2,6-Difluoro-4-pyridinecarboxylic acid (DFPMA), to form a multifunctional buried interface to achieve high-performance PSCs. The introduction of DFPMA can construct π-π stacking with Me-4PACz and simultaneously interact with Pb²⁺ and FA⁺ ions of perovskites, resulting in a uniform surface potential of HTLs, enhanced carrier transport, reduced defect density, and improved film quality of the perovskite. Consequently, the final PSCs present a champion efficiency of 25.46%, along with a significantly enhanced lifetime. The target device can maintain 91% of its initial efficiency after storage in a nitrogen environment for 1000 h and keep 87% efficiency after MPP tracking for around 950 h. This work provides a promising way for developing more effective buried interfaces for the advancement of PSCs.