Incorporating an Aromatic Cationic Spacer to Assemble 2D Polar Perovskite Crystals toward Self-Powered Detection of Quite Weak Polarized Light

Two-dimensional (2D) hybrid perovskites
with intrinsic attributes
of structural and optical anisotropy are holding a bright promise
for polarization-sensitive photodetection. However, studies on self-powered
detection to quite weak polarized light remain scarce in this 2D family.
By incorporating an aromatic spacer into the 3D cubic prototype, we
have successfully assembled a new 2D hybrid perovskite with a polar
motif, (FPEA)2(MA)­Pb2I7 (FMPI, where FPEA is 4-fluorophenethylammonium and MA is methylammonium).
Its unique 2D quantum-well structure allows optical absorption dichroism
with a large ratio of ∼3.15, and the natural polarity results
in a notable bulk photovoltaic effect. Further, centimeter-size crystals
(10 × 10 × 3 mm3) of FMPI were facilely
obtained by the temperature cooling method, and its crystal-based
detectors enable excellent self-powered detection of quite weak polarized
light, showing a notable polarization-sensitive ratio (∼1.5),
extremely low detection limit (∼100 nW/cm2), and
antifatigued stability. The alloyed aromatic cationic spacers facilitate
the polarity and enhanced phase stability. This study paves a way
for further exploration of new 2D perovskite candidates toward optoelectronic
device applications.