Anisotropic carrier diffusion in single MAPbI3 grains correlates to their twin domains,Energy & Environmental Science

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Anisotropic carrier diffusion in single MAPbI3 grains correlates to their twin domains
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2020-06-02 , DOI: 10.1039/d0ee01016b
Ilka M. Hermes _{1,

2,

3} , Andreas Best _{1,

2,

3} , Leonard Winkelmann _{1,

2,

3,

4,

5} , Julian Mars _{1,

2,

3} , Sarah M. Vorpahl _{6,

7,

8,

9} , Markus Mezger _{1,

2,

3,

4,

5} , Liam Collins _{9,

10,

11,

12} , Hans-Jürgen Butt _{1,

2,

3} , David S. Ginger _{6,

7,

8,

9} , Kaloian Koynov _{1,

2,

3} , Stefan A. L. Weber _{1,

2,

3,

4,

5}

Affiliation

Polycrystalline thin films and single crystals of hybrid perovskites – a material group successfully used for photovoltaic and optoelectronic applications – reportedly display heterogeneous charge carrier dynamics often attributed to grain boundaries or crystalline strain. Here, we locally resolved the carrier diffusion in large, isolated methylammonium lead iodide (MAPbI₃) grains via spatial- and time-resolved photoluminescence microscopy. We found that the anisotropic carrier dynamics directly correlate with the arrangement of ferroelastic twin domains. Comparing diffusion constants parallel and perpendicular to the domains showed carriers diffuse around 50–60% faster along the parallel direction. Extensive piezoresponse force microscopy experiments on the nature of the domain pattern suggest that the diffusion anisotropy most likely originates from structural and electrical anomalies at ferroelastic domain walls. We believe that the domain walls act as shallow energetic barriers, which delay the transversal diffusion of carriers. Furthermore, we demonstrate a rearrangement of the domains via heat treatment above the cubic-tetragnal phase transition. Together with the previously reported strain engineering via external stress, our findings promise additional routes to tailor the directionality of the charge carrier diffusion in MAPbI₃-based photovoltaics and optoelectronics as well as other ferroelastic materials for optoelectronic applications.

中文翻译：

单个MAPbI3晶粒中各向异性载流子的扩散与其双畴相关

据报道，复合钙钛矿的多晶薄膜和单晶（一种成功用于光伏和光电应用的材料组）显示出通常归因于晶界或晶体应变的异质载流子动力学。在这里，我们局部分辨在大，中分离甲基铵碘化铅的载流子扩散（MAPbI ₃）晶粒经由空间和时间分辨的光致发光显微镜。我们发现各向异性载流子动力学与铁弹性双畴的排列直接相关。比较平行于和垂直于畴的扩散常数，可以发现载流子沿平行方向的扩散速度快了50-60％。关于畴模式性质的广泛的压电响应力显微镜实验表明，扩散各向异性最有可能源自铁弹性畴壁的结构和电异常。我们认为，畴壁起着浅能量屏障的作用，这延迟了载流子的横向扩散。此外，我们证明了域的重排通过立方四方相变以上的热处理。与先前报道的通过外部应力进行的应变工程一起，我们的发现有望为在基于MAPbI ₃的光伏和光电以及用于光电应用的其他铁弹性材料中调整载流子扩散的方向性提供更多途径。

更新日期：2020-06-02

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