New Room-Temperature Ferroelectrics with Photoluminescent Properties

Organic–inorganic hybrid materials
are highly versatile
and can be easily modified, allowing for the deliberate construction
of multifunctional ferroelectrics. In particular, the combination
of photoluminescence and ferroelectricity in a single hybrid material
holds great potential for various applications, such as lighting sensors,
memory devices, and other multifunctional uses. In this study, we
focused on 3-oxa-8-azabicyclo[3.2.1]octane hydrochloride (OAO) and
designed two room-temperature ferroelectrics based on manganese (Mn):
OAO-MnCl4 ((C6H12NO)2MnCl4·H2O) and OAO-MnBr4 ((C6H12NO)2MnBr4·H2O).
Both of these compounds crystallize in the polar orthogonal space
group Pna21, displaying robust photoluminescence
and ferroelectricity at room temperature. The saturation polarizations
of OAO-MnCl4 and OAO-MnBr4 are approximately
0.51 and 0.59 μC/cm2, respectively. Interestingly,
the single crystal of OAO-MnCl4 demonstrates dual-emission
bands at 550 and 670 nm, which are attributed to self-trapped excitons.
Additionally, OAO-MnCl4 exhibits a reversible thermochromic
phenomenon, displaying sensitive luminescent switching between green
and red emissions within a narrow temperature range. This room-temperature
molecular ferroelectric with photoluminescence opens up new avenues
for designing novel multifunctional ferroelectrics and establishes
a foundation for potential optoelectronic applications of these luminescent
Mn-based materials.