Flexoelectricity has become an emerging tool to tailor the material properties. The flexoelectric modulation of ferroelectric photovoltaic (FEPV) properties is of particular interest, because it offers an opportunity to boost the photovoltaic efficiency. In most previous studies, the flexoelectric effect is generated by local pressing or macroscopic bending, which, however, results in a local or weak modulation of the FEPV behavior. Here, a significant modulation of the FEPV effect by the strain-relaxed epitaxy (SRE)-induced giant macroscopic flexoelectric effect is demonstrated. Using SRE, giant strain gradients (>10⁷ m⁻¹) are generated and tuned in ferroelectric Pb(Zr_0.2Ti_0.8)O₃ epitaxial films. Tuning the giant strain gradient can significantly modify the switchable FEPV properties. Particularly, a photovoltage enhancement as large as ≈0.5 V is achieved. It is suggested that the flexoelectric modulation of FEPV behavior may originate from the flexoelectric polarization-induced depolarization field. This study highlights the immense application potential of the SRE-induced flexoelectricity in the engineering of functional thin-film devices.

中文翻译：

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由应变松弛外延引起的巨大宏观柔性电效应对铁电光伏行为的显着调制

柔性电已成为调整材料特性的新兴工具。铁电光伏 (FEPV) 特性的挠曲电调制特别令人感兴趣，因为它提供了提高光伏效率的机会。在大多数先前的研究中，挠曲电效应是由局部挤压或宏观弯曲产生的，然而，这会导致 FEPV 行为的局部或弱调制。在这里，证明了应变松弛外延（SRE）诱导的巨大宏观挠曲电效应对 FEPV 效应的显着调制。使用 SRE，在铁电 Pb(Zr _0.2 Ti _0.8 )O ₃中产生和调整巨大的应变梯度 (>10 ⁷ m ^-1 )外延膜。调整巨大的应变梯度可以显着改变可切换的 FEPV 特性。特别是，实现了高达 ≈0.5 V 的光电压增强。这表明 FEPV 行为的挠曲电调制可能源于挠曲极化诱导的去极化场。这项研究突出了 SRE 诱导的挠曲电在功能性薄膜器件工程中的巨大应用潜力。