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

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.