Combining π-Conjugation and Cation−π Interaction for Water-Stable and Photoconductive One-Dimensional Hybrid Lead Bromide

Abstract

Hybrid lead halide perovskites and their derivatives are important optoelectronic materials but suffer from water instability. Combining both the optoelectronics and the water stability of such systems is a major challenge in material design today. To address this issue, we employ the well-known π-conjugation and cation−π interaction concepts in designing a hybrid lead halide perovskite derivative system. (4,4′-VDP)Pb₂Br₆ (VDP = vinylenedipyridinium) single crystals are prepared. They have a one-dimensional (1D) arrangement of inorganic Pb–Br sublattices connected via the 4,4′-VDP organic sublattice. The π-conjugation in the 4,4′-VDP sublattice allows electronic communication between the 1D Pb–Br units, reducing the band gap and improving the photoconductivity. Importantly, N⁺ of one 4,4′-VDP molecular ion interacts with the π-electron cloud of the adjacent one. This intermolecular cation−π interaction extends throughout the organic sublattice, making the hybrid crystal stable when stored under water for more than a year without requiring any encapsulations.