Organic-Inorganic Hybrid Ammonium Halogenobismuthates and their Piezoelectric Properties

Abstract

Organic-inorganic hybrid perovskite materials have been widely used due to their unique properties, such as their biocompatibility, photovoltaic, piezo-, pyro- and ferroelectric properties. Their numerous utilizations include solar cells, charge storage capacitors, MEMS, field-effect transistors, resonators, sensors, etc., making them an exciting topic of research. Traditional lead oxide-based ferroelectrics are the most used materials for these applications, but they lead to certain environmental concerns regarding the recycling and disposal of devices. Additionally, literature has many polymers like polyvinylidene difluoride (PVDF) based nanogenerator devices with excellent output performances. But PVDF-based nanogenerators require external additives like poling, annealing etc., to enhance their mechanical outputs. Hence it is highly desirable to prepare all-organic or hybrid organicinorganic materials with mouldable optical properties and with no toxic metal ion contents for future generation electronics. Here in, we have synthesized two halogenobismuthates(III) molecular–ionic complexes with the general formula A2MX5 and A3M2X9, which are ferroelectric active and can find their extensive applications in piezoelectric nanogenerator devices. The compound [BrPhBnN(Me)2]2. [BiBr5] (1) and [BrPhMeBnN(Me)2]3.[Bi2Br9] (2) were crystallised in orthorhombic Pna21 and Pca21 space groups respectively. The composite nanogenerator devices of 1 and 2 in polylactic acid (PLA) gave maximum peakto-peak voltages (VPP) of 26.2 V and 24.2 V respectively. Also the maximum power density values were calculated to be 41.81 and 61.88 µW.cm-2 for the optimal 15 wt% 1-PLA and 10 wt% 2-PLA devices, respectively. For compound 1, 14 and 114 μC charges and 10 and 64 μJ of energy have been stored, respectively, for 10 and 100 μF capacitors. While for compound 2, 2.03 and 18.92 μC charges and 0.20 and 1.78 μJ of energy has been stored in 10 and 100 μF capacitors, respectively