Anion‐Dependent Polarization and Piezoelectric Power Generation in Hybrid Halide MAPbX₃ (X = I, Br, and Cl) Thin Films with Out‐of‐Plane Structural Adjustments

Abstract

Anion-dependent differences in the electromechanical energy harvesting capability of perovskite halides have not been experimentally demonstrated thus far. Herein, anion-dependent piezoelectricity and bending-driven power generation in high-quality methylammonium lead halide MAPbX 3 (X = I, Br, and Cl) thin films are explored; additionally, anisotropic in situ strain is imposed to improve energy harvesting under tensile bending. After applying the maximum in situ strain of −0.73% for all the halide thin films, the MAPbI 3 thin-film harvester exhibited a peak voltage/current of ≈23.1 V/≈1703 nA as the best values, whereas MAPbBr 3 and MAPbCl 3 demonstrated ≈5.6 V/≈176 nA and ≈3.3 V/≈141 nA, respectively, under identical bending conditions. Apart from apparent ferroelectricity of tetragonal MAPbI 3 , origin of the piezoelectricity in both cubic MAPbBr 3 and MAPbCl 3 is explored as being related to organic-inorganic hydrogen bonding, lattice distortion, and ionic migration, with experimental supports of effective piezoelectric coefficient and grain boundary potential. Conclusively, piezoelectricity of the cubic halides is assumed to be due to their soft polarity modes and relatively low elastic modulus with vacancies contributing to space-charge polarization. In the case of ferroelectric MAPbI 3 , the distortion of PbI 6 octahedra and atomic displacement within each octahedron are quantitatively estimated.

High-performance piezoelectric energy harvesting in amorphous perovskite thin films deposited directly on a plastic substrate

“…As the best thin-film harvester thus far, the thin-film cantilever of 2.8-μmthick Pb(Zr,Ti)O 3 prepared by sputtering delivered 244 μW and 1.1 × 10 6 μW cm −3 as a result of mechanical vibration at a resonant frequency of 50 Hz 3 . Another noticeable generation result of 182 μW and 2.7 × 10 5 μW cm −3 by bending was reported for flexible 486-nm-thick methylammonium lead iodide (MAPbI 3 ) films on an ITO-PEN substrate 70 . In addition, our best harvesting performance was compared to the power-generation outcomes reported for polymer-matrix composite harvesters where piezoelectric materials such as PZT, BaTiO 3 , and perovskite halides are incorporated as fillers in various polymer matrices as listed in Supplementary Table 5 [72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] .…”

“…, ZnO 65 , AlN 66,67 , and perovskite halides [68][69][70][71] , which were characterized by different measurement techniques utilizing vibration, pressing, and bending. In the case of thin films on rigid substrates, the vibrational operation is used for the cantilevers with the optimized effect at the specific resonant frequency, while the flexible harvesters on polymer substrates utilize the mechanical input sources typically from pressing or bending.…”

Piezoelectric Charge Coefficient of Halide Perovskites

“…These studies show that the poling process enhances the electrical output from the piezoelectric devices based on halide materials and enhances the d 33 values. The origin of d 33 enhancement is mainly ascribed to the increased BX 6 octahedral distortion in the lattice and the off-centring of the B atoms [58,60,62]. Chen et al [45] and Khan et al [61] reported that applying a poling voltage of 3 V and 40 V during the PFM measurement was enough to observe the domain switching during the PFM measurement.…”