Photovoltaic energy as one of the important alternatives to traditional fossil fuels has always been a research hot spot in the field of renewable and clean solar energy. Very recently, the anomalous ferroelectric photovoltaic effect in multiferroic bismuth ferrite (BiFeO₃) has attracted much attention due to the above-bandgap photovoltage and switchable photocurrent. However, its photocurrent density mostly in the magnitudes of μA/cm² resulted in a poor power conversion efficiency, which severely hampered its practical application as a photovoltaic device. In this case, a novel approach was designed to improve the photocurrent density of BiFeO₃ through the cooperative effect of the gradient distribution of oxygen vacancies and consequently induced the flexoelectric effect realized in the (La, Co) gradient-doped BiFeO₃ multilayers. Subsequent results and analysis indicated that the photocurrent density of the gradient-doped multilayer BiFeO₃ sample was nearly 3 times as much as that of the conventional doped single-layer sample. Furthermore, a possible mechanism was proposed herein to demonstrate roles of band engineering and the flexoelectric effect on the photovoltaic performance of the gradient-doped BiFeO₃ film.

中文翻译：

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集成能带工程和由铋铁氧体薄膜中的高光电流密度组成梯度引起的挠曲电效应

光伏能源作为传统化石燃料的重要替代品之一，一直是可再生清洁太阳能领域的研究热点。最近，多铁性铋铁氧体 (BiFeO ₃ ) 中的异常铁电光伏效应由于高于带隙的光电压和可切换的光电流而引起了很多关注。然而，其光电流密度大多在μA/cm ²量级，导致功率转换效率低下，严重阻碍了其作为光伏器件的实际应用。在这种情况下，设计了一种新方法来提高 BiFeO ₃的光电流密度通过氧空位梯度分布的协同效应，从而诱导在（La，Co）梯度掺杂的 BiFeO ₃多层中实现的挠曲电效应。随后的结果和分析表明，梯度掺杂多层 BiFeO ₃样品的光电流密度几乎是常规掺杂单层样品的 3 倍。此外，本文提出了一种可能的机制来证明能带工程和挠曲电效应对梯度掺杂的 BiFeO ₃薄膜的光伏性能的作用。