AI 中文总结
研究二维混合钙钛矿铁电体中BPE行为，发现其EBPE沿垂直非极性方向比极性面内方向高两个数量级。源于独特耦合产生强BPE响应及不同行为，还开发公式描述光电压现象，适用于该新型铁电体家族等。
AI 中文摘要
体光伏效应（BPE）的光伏电场反映了铁电体将光激发激子分离为电子和空穴的内在能力，是电压读出光电探测器等应用的重要参数。由于极化定义了阳离子 - 阴离子位移和非中心对称轴，极性方向通常是表现出强大体积光伏场（EBPE）的取向之一。本文报道了二维混合钙钛矿铁电体（HPFs）中出现的BPE行为，其中EBPE沿垂直非极性方向比沿极性面内方向高两个数量级。其大小比不同材料体系的基准光铁电体高出几个数量级，是迄今为止报道的二维HPFs中最高的。这种具有出现的方向各向异性的强BPE响应源于转移电流BPE机制、高效光载流子产生的无机部分和绝缘体状有机部分之间的独特耦合，这种组合在传统光铁电体中是相互矛盾或无法实现的。这种成分和各向异性还产生了与典型光铁电体不同的基本BPE行为，包括激光强度依赖的光电压和光电压与材料尺寸的非线性缩放。我们分析并开发了一系列公式来描述出现的光电压现象，这些公式应适用于这个新型二维铁电体家族以及具有类似各向异性和强大光电响应的极性系统。
英文摘要
The photovoltaic electric field of the bulk photovoltaic effect (BPE) reflects the intrinsic ability of ferroelectrics to separate photoexcited excitons into electrons and holes, and are essential parameters for applications such as voltage-readout photodetectors. Because polarization defines the cation-anion displacement and noncentrosymmetric axis, the polar direction is generally one of the orientations exhibiting strong bulk photovoltaic field (EBPE). Here, we report emergent BPE behavior in 2D hybrid perovskite ferroelectrics (HPFs), where EBPE can be two orders of magnitude higher along the vertical nonpolar direction than along the polar in-plane direction. Its magnitude is up to orders of magnitude higher than that of benchmark photoferroelectrics across different material systems and is the highest among 2D HPFs reported so far. This strong BPE response with emergent directional anisotropy originates from the unique coupling among the shift-current BPE mechanism, an efficient photocarrier-generating inorganic part, and an insulator-like organic part, a combination that is conflicting or inaccessible in traditional photoferroelectrics. This composition and anisotropy also produce basic BPE behavior distinct from that of typical photoferroelectrics, including a laser intensity dependent photovoltage and a nonlinear scaling of photovoltage with material dimension. We analyze and develop a series of formulas to describe the emergent photovoltage phenomena, which should be applicable to this novel 2D ferroelectrics family and to polar systems with similar anisotropy and robust photoelectric response.
