Orientation‐Engineered Interfacial Bi‐Anchoring Molecules for Efficient and Stable Perovskite Solar Cells

Self‐assembled monolayers as hole‐transport materials have been a milestone in the advancement of inverted perovskite solar cells (PSCs). However, its strong‐acidity and weak‐interface‐bonding inherences remain great challenges for commercially desirable PSCs. To overcome the limitation, we proposed the orientation‐engineered interfacial bi‐anchoring molecules with a symmetric linear donor–acceptor–donor (D–A–D) structured N‐oxide‐based building block. The D–A–D structure with intramolecular push–pull electron effects features superior hole‐selective ability than the widely used donor units, endowing effective hole‐transport planar. However, the bilateral N‐oxide functional groups (N + ‐O − ) in the acceptor bipyridine introduce a steric effect to drive the D–A–D planar in both in‐plane and out‐of‐plane directions, effectively promoting the hole extraction. Moreover, the reversely oriented N + ‐O − function groups can firmly adsorb on ITO substrate and perovskite buried surface, respectively, constructing an interfacial bi‐anchoring connection. This molecular configuration considerably promotes the photothermal tolerance, connective strength as well as energy‐level alignment at perovskite/HTLs interface, enabling superior charge extraction and durability. Consequently, BPyDO‐TPA‐based inverted PSCs achieve an impressive efficiency of 26.53%, ranking as one of the highest efficiencies among nonphosphonic acid small‐molecule transporting materials. BPyDO‐TPA‐based devices also demonstrate excellent operational stability, retaining 94.82% of its initial efficiency after MPP tracking for 1000 h at 85 °C.