Multifunctional\nAction Site Strategy of a Buried Interface\nfor High-Performance Perovskite Solar Cells

The buried interface is pivotal for enhancing both the\nefficiency\nand stability of p-i-n perovskite solar cells (PSCs). This is because\ncarrier extraction and recombination processes can be significantly\naffected by the defects that tend to form on the bottom side. Herein,\na dual-reaction site molecule homopiperazine-1,4-bis (2-ethanesulfonic\nacid) (HEA) is employed as an effective multifunctional passivator\nfor a self-assembled monolayer (SAM)/perovskite interface for the\ninverted PSCs. The HEA molecule has two sulfonic acid groups with\ndouble action sites, which can effectively fill the ITO vacancies\nunanchored by SAM and simultaneously passivate the uncoordinated Pb<sup>2+</sup> defects of perovskite to form an effective molecular bridge,\nachieving full coverage of the substrate and orderly crystallization\nof perovskites. The resultant device presented satisfactory efficiencies\nof 25.71% (0.0982 cm<sup>2</sup>) and 24.26% (1 cm<sup>2</sup>). Our\ndevice retained 91.8% of its initial power conversion efficiency (PCE)\nafter 1000 h of operation under 1-sun illumination in a nitrogen atmosphere.\nThis research offers important insights into further refinement and\nenhancement of buried interfaces in PSCs.