Ferroelectric Domain Wall Induced Band Gap Reduction and Charge Separation in Organometal Halide Perovskites
Ferroelectric Domain Wall Induced Band Gap Reduction and Charge Separation in Organometal Halide Perovskites
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DOI：
10.1021/jz502666j
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发表时间：
2015-02-19
影响因子：
5.7
通讯作者：
Rappe, Andrew M.
中科院分区：
文献类型：
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作者：
Liu, Shi;Zheng, Fan;Rappe, Andrew M.
有机金属卤化物钙钛矿在过去的S年中得到了深入的研究，受到其经认证的高光伏功率转换效率的启发。这些材料中的一些是室温铁电体。最近，通过压电响应力显微镜观察到甲基铵三碘化铅（CH 3 NH3 PbI 3）中存在可切换的铁电畴。本文重点研究了CH_3NH_3PbX_3（X = Cl，Br，I）铁电畴壁的结构和电子性质。我们发现，有机金属卤化物钙钛矿可以形成带电和不带电的畴壁，由于灵活的取向顺序的有机分子。用密度泛函理论计算了具有180和90个畴壁的畴结构的电子带隙。发现带电畴壁的存在将使带隙显著减小20- 40%，而不带电畴壁的存在对带隙没有实质性影响。我们证明了带电畴壁可以作为电荷载流子运动的隔离通道。这些结果突出了铁电畴壁在光伏应用中的混合钙钛矿的重要性，并提出了通过畴图案化进行器件优化的可能途径。
Organometal halide perovskites have been intensely studied in the past S years, inspired by their certified high photovoltaic power conversion efficiency. Some of these materials are room-temperature ferroelectrics. The presence of switchable ferroelectric domains in methylammonium lead triiodide, CH3NH3PbI3, has recently been observed via piezoresponse force microscopy. Here, we focus on the structural and electronic properties of ferroelectric domain walls in CH3NH3PbX3 (X = Cl, Br, I). We find that organometal halide perovskites can form both charged and uncharged domain walls due to the flexible orientational order of the organic molecules. The electronic band gaps for domain structures possessing 180 and 90 walls are estimated with density functional theory. It is found that the presence of charged domain walls will significantly reduce the band gap by 20-40%, while the presence of uncharged domain walls has no substantial impact on the band gap. We demonstrate that charged domain walls can serve as segregated channels for the motions of charge carriers. These results highlight the importance of ferroelectric domain walls in hybrid perovskites for photovoltaic applications and suggest a possible avenue for device optimization through domain patterning.