Enrichment of anchoring sites by introducing supramolecular halogen bonds for the efficient perovskite nanocrystal LEDs

Considering the multi-functionalization of ligands, it is crucial for ligand molecular design to reveal the landscape of anchoring sites. Here, a typical triphenylphosphine (TPP) ligand was employed to explore its effect on the surface of CsPbI3 perovskite nanocrystals (PNCs). Except for the conventionally considered P-Pb coordination, an P-I supramolecular halogen bonding was also found on the NC surface. The coexistence of the above two types of bonding significantly increased the formation energy of iodine vacancy defects and improved the photoluminescence quantum yield of PNCs up to 93%. Meanwhile, the direct interaction of P and I enhanced the stability of the Pb-I octahedra and dramatically inhibited the migration of I ions. Furthermore, the introduction of additional benzene rings (2-(Diphenylphosphino)-biphenyl (DPB)) increased the delocalized properties of the PNC surface and significantly improved the charge transport of the PNCs. As a result, the DPB passivated CsPbI3 NCs based top-emitting LEDs exhibite a peak external quantum efficiency (EQE) of 22.8%, a maximum luminance of 15, 204 cd m-2, and an extremely low-efficiency roll-off of 2.6% at the current density of 500 mA cm-2.