Abstract In this work, we proposed modification of BiFeO3 (BFO) by Mn and Ca co-doping, and realized the epitaxial growth of Bi0.98Ca0.02Fe0.95Mn0.05O3 (BCFMO) thin films on (1 0 0)-oriented SrTiO3 (STO) substrates with a SrRuO3 (SRO) buffer layer via pulsed laser deposition (PLD). A decreased bandgap (Eg = 2.41 eV) and enhanced remanent polarization (Pr = 92.5 μC/cm2) were simultaneously achieved in the BCFMO thin film. A tunable photovoltaic (PV) effect by changing the direction of the poling electric field was observed in the BCFMO-based device. We investigated the PV mechanism for the device by analyzing its band structure and attribute it to the coupling effects of the ferroelectric depolarization field and the interface Schottky barriers. The BCFMO-based device under favorable upward poling shows the best PV performance with an open-circuit voltage (Voc) of −0.29 V and short-circuit current density (Jsc) of 0.26 mA/cm2, which are much higher than those for the BFO-based device (Voc = -0.11 V, Jsc = 0.08 mA/cm2), resulting from the narrower bandgap and larger Pr in the BCFMO film. The approach of simultaneously introducing Ca and Mn into the BFO, enabling both a higher polarization and narrower bandgap, opens a new way for improving the performance of BFO-based PV devices.

中文翻译：

---

Ca和Mn共掺杂BiFeO3外延薄膜中增强的光伏效应

摘要 在这项工作中，我们提出了通过 Mn 和 Ca 共掺杂对 BiFeO3 (BFO) 进行改性，并在 (1 0 0) 取向的 SrTiO3 上实现了 Bi0.98Ca0.02Fe0.95Mn0.05O3 (BCFMO) 薄膜的外延生长。 (STO) 基板通过脉冲激光沉积 (PLD) 具有 SrRuO3 (SRO) 缓冲层。在 BCFMO 薄膜中同时实现了带隙减小（Eg = 2.41 eV）和剩余极化增强（Pr = 92.5 μC/cm2）。在基于 BCFMO 的器件中观察到通过改变极化电场方向的可调谐光伏 (PV) 效应。我们通过分析其能带结构研究了该器件的 PV 机制，并将其归因于铁电去极化场和界面肖特基势垒的耦合效应。在有利的向上极化下，基于 BCFMO 的器件显示出最佳的 PV 性能，开路电压 (Voc) 为 -0.29 V，短路电流密度 (Jsc) 为 0.26 mA/cm2，远高于基于 BFO 的器件（Voc = -0.11 V，Jsc = 0.08 mA/cm2），由 BCFMO 薄膜中更窄的带隙和更大的 Pr 产生。同时将 Ca 和 Mn 引入 BFO 的方法可以实现更高的极化和更窄的带隙，为提高基于 BFO 的光伏器件的性能开辟了一条新途径。