Emergence of ambient temperature ferroelectricity in meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride thin films

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Here, we demonstrate that the meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride, [H2TMPyP]4+Cl4, with a face-to-face orientation directed along a single direction displays ferroelectric properties at room temperature. This is attributed to its spontaneous polarization, due to an extensive hydrogen-bonded network. From C-V measurements, a remnant polarization of approximately 0.5 μC cm−2 was estimated for pristine porphyrin film, which increases linearly up to about 1.7 μC cm−2 after applying 2 V at the top electrode and further to 9.6 μC cm−2 after 5 V positive poling. This large—for practical utilization—level of remnant polarization of [H2TMPyP]4+Cl4 makes it promising for future applications.