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.

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Piezoelectric energy harvesters based on Pb(Zr0.5Ti0.5)O3 (PZT) ceramics have been extensively studied for various low‐power applications. Herein, unprecedented multiple‐harvester structures with record‐breaking performance are proposed for targeting nonresonant‐frequency or extremely low‐frequency applications. Exceptional combinations of PZT with three different relaxor materials, namely, Pb(Co1/3Nb2/3)O3 (PCN), Pb(Ni1/3Nb2/3)O3 (PNN), and Pb(Zn1/3Nb2/3)O3 (PZN), are systematically investigated in terms of their structural changes and piezoelectricity. Following the optimization of the PCN–PZT, PNN–PZT, and PZN–PZT systems in terms of piezoelectricity and power generation, a few device structures are designed using the advantages of each system. For example, the highest g31 composition of 0.2PCN–0.8PZT is combined with the highest d31 of 0.4PZN–0.6PZT to maximize the power generation in the two‐parallel‐tape structure. Multilayer harvester structures with up to four layers are also evaluated to correlate the enhanced voltage and current with the layer thickness and effective area for surface‐charge polarization. The four‐layer 0.4PZN‐0.6PZT unimorph cantilever demonstrates exceptional energy‐harvesting performance of ≈535.9 µW, corresponding to the record power density of ≈10 mW cm−2 g−2 Hz−1 at 2 Hz. The outstanding outcome is believed to be a benchmark for various nonresonant‐frequency applications.