Pan Dan-Feng, Bi Gui-Feng, Chen Guang-Yi, Zhang Hao, Liu Jun-Ming, Wang Guang-Hou, Wan Jian-Guo
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China.
Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
Sci Rep. 2016 Mar 8;6:22948. doi: 10.1038/srep22948.
Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.
最近，铁电钙钛矿氧化物因其在太阳能转换领域的潜在应用而备受关注。然而，目前报道的铁电光伏效应的功率转换效率远低于预期值。关键问题之一在于两个背靠背的肖特基势垒，它们在铁电体 - 电极界面处形成，阻碍了大部分光生载流子到达外部电路。在此，我们通过引入极化依赖的界面耦合效应，开发了一种增强铁电光伏效应的新方法。通过在铁电ITO/PZT/Au薄膜中插入具有自发极化的半导体ZnO层，形成了具有强极化依赖界面耦合效应的p-n结。异质结构的功率转换效率提高了近两个数量级，极化调制率提高了约四倍。结果表明，极化依赖的界面耦合效应会导致异质结构能带结构发生巨大变化，不仅产生对齐的内电场，还能调节PZT-ZnO界面处的耗尽层宽度和势垒高度。这项工作为开发高效的铁电基太阳能电池和新型光电器件提供了一种有效途径。
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