Optimizing Molecular Packing and Interfacial Contact via Halogenated N‐Glycidyl Carbazole Small Molecules for Low Energy Loss and Highly Efficient Inverted Perovskite Solar Cells

Abstract Nonideal interfacial contact and non‐radiative voltage loss in self‐assembled monolayers (SAMs)‐based inverted perovskite solar cells (PSCs) limit their further development. Herein, two carbazole‐based molecules with different halogen atoms (X‐OCZ, X = Cl or Br) are developed as efficient interfacial regulators. The halogen effect not only finely modulates the molecular packing, crystallinity, and surface contact potential of the MeO‐2PACz analogue via self‐induced intermolecular interactions but also significantly influences the subsequent crystal growth of perovskite, thus resulting in the formation of high‐quality films with enhanced crystallinity, improved energy level alignment, and depressed non‐radiative recombination. Importantly, the Cl‐OCZ‐mediated device exhibits a minimal interfacial carrier transport energy barrier of 0.10 eV and an impressive charge collection efficiency of 93.6%. Moreover, the target device (aperture area: 0.09 cm 2 ) shows an exceptional efficiency of 26.57% (certified 26.4%) along with enhanced thermal and operational stability. The strategy is also extended to large area devices, delivering efficiencies of 25.0% for a 1 cm 2 device and 22.9% for a 12.96 cm 2 minimodule. This study highlights the halogen role of interfacial small molecules in optimizing molecular packing and interfacial contact toward highly efficient PSCs with minimized energy loss and non‐radiative recombination.