A novel, lead-free halide perovskite derivative for ferro- and piezo-electric applications
Esther Yi-Hang Hung a, Harry Sansom b, Henry Snaith a
a Department of Physics, University of Oxford, UK
b University of Bristol, School of Chemistry
Oral, Esther Yi-Hang Hung, presentation 107
Publication date: 6th February 2024

Piezoelectricity is the phenomena of strain-induced electric polarization or vice versa; electric-field induced strain, with applications ranging from actuators, to vibrational energy harvesters. Organic-inorganic hybrid (OIH) ferro- and piezo-electric materials have recently attracted interest over traditional piezo-ceramics due to simpler processing methods, their light-weight nature, mechanical flexibility and lower toxicity compared to traditional ceramics [1,2,3]. Recent reports have shown that by incorporation of a ferroelectric OIH perovskite into a (FA,MA)Pb(I,Br)3 perovskite solar cell device, and poling it, a higher fill factor and VOC is achieved via suppression of interfacial recombination due to ferroelectricity-induced modification of the built-in field [4]. Further, molecular ferro- and piezo-electrics often have bandgaps within the optical range, and have thus been studied for their anomalous photovoltaic properties arising from their intrinsic non-centrosymmetry which allows for above-bandgap open-circuit voltage (VOC) to be measured [5]. Here, we design a novel, stable lead-free semiconducting hybrid ferroelectric OBI, by inserting a polar, quaternary ammonium organic cation, named ‘O’ into a face-sharing, BiI6 anionic framework to form O3B2I9 (OBI). OBI crystallizes in a polar space group at room temperature, and exhibits a band gap within the optical range (2.3 eV), in close agreement with that calculated from first-principles methods. Piezoresponse force microscopy (PFM), polarization hysteresis loops and pyroelectric measurements on both single crystals and thin films of OBI reveal its ferroelectric nature, indicating potential applications for flexible self-powered electronics or bio-sensors as well as for ferroelectricity-induced enhancements to the performance of perovskite solar cells.

E.Y.-H.H. thanks Xaar for PhD scholarship sponsorship. 

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