Formamidinium Perovskitizers and Aromatic Spacers Synergistically Building Bilayer Dion–Jacobson Perovskite Photoelectric Bulk Crystals

Two-dimensional
(2D) multilayer Dion–Jacobson (DJ) phase
organic inorganic hybrid perovskites (OIHPs) have attracted extensive
research attention due to the high stability and excellent charge-transport
properties in the optoelectronic field. However, the synthesis of
2D multilayer DJ OIHPs is still very challenging. Until now, only
few multilayer DJ perovskites have been reported and most of them
are based on volatile methylamine (MA) cations. Compared with MA-based
OIHPs, the OIHPs constructed with formamidinium (FA) as perovskitizers
not only improve the stability but also extend the light absorption
range. Meanwhile, the introducing aromatic diamines as spacers could
promote the electron–hole separation in such DJ hybrids. However,
the DJ OIHP bulk single crystal constructed by using the advantages
of FA as perovskitizers and aromatic diamines as spacers is still
blank. Herein, we integrate the properties of organic cations and
inorganic skeletons at a molecular-scale to construct a broadband-responsive
2D bilayer DJ perovskite (3AMPY)­(FA)­Pb2I7 [3AMPY
= 3-(aminomethyl)­pyridinium], which shows a fascinating detectivity
from X-ray (5.23 × 104 μC Gyair–1 cm–2 at 200 V bias) and visible
light (6 × 1012 jones at 637 nm) to the near-infrared
region (2.6 × 109 jones at 780 nm). After an in-depth
analysis of structure and optical properties, we found that the distortion
degree of Pb–I–Pb bond angles between adjacent PbI6 octahedra plays a crucial role on optical properties; on
the other hand, the interlayer spacer cations (3AMPY) and intralayer
perovskitizers (FA) mutual participate in the contribution of the
conduction band, making (3AMPY)­(FA)­Pb2I7 have
a narrow optical band gap of 1.54 eV. Such a 2D perovskite material
with a wide spectra response will be the preferred choice for photodetection
under complex conditions.