Lead-Halide Perovskites Meet Donor–Acceptor Charge-Transfer Complexes

Low-dimensional
lead halide hybrid perovskites are nowadays in
the spotlight because of their improved stability and extensive chemical
flexibility compared to their 3D perovskite counterparts, the current
challenge being to design functionalized organic cations. Here, we
report on the synthesis and full characterization of a perovskite-like
hybrid (a perovskitoid) where the 1D lead iodide layout is patterned
with a donor–acceptor charge transfer complex (CTC) between
pyrene and tetracyanoquinodimethane, with a chemical formula of (C20H17NH3)­PbI3·(C12H4N4). By combining multiple structural
analysis and spectroscopic techniques with ab initio modeling, we
show that the electronic, optical, and charge-transport properties
of the hybrid materials are dominated by the organic CTC, with the
inorganic backbone primarily acting as a template for the organization
of the donor and acceptor molecules. Interestingly, time-resolved
microwave conductivity (TRMC) measurements show an enhanced photocurrent
generation in the 1D hybrid compared to the pure organic charge-transfer
salt, likely associated with transient localization of the holes on
the lead-iodide octahedra. This observation is in line with the close
energy resonance between the valence crystal orbitals of the lead-iodide
lattice and the frontier occupied molecular orbitals of pyrene predicted
by the DFT calculations. Therefore, it paves the way toward the design
of new hybrid low-dimensionality perovskites offering a synergic combination
of organic and inorganic functionalities.