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Orientation and Grain Size in MAPbI3 Thin Films: Influence on Phase Transition, Disorder, and Defects
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2023-05-30 , DOI: 10.1021/acs.jpcc.2c08968
Christina Witt 1 , Konstantin Schötz 1 , Meike Kuhn 2 , Nico Leupold 3 , Simon Biberger 1 , Philipp Ramming 1 , Frank-Julian Kahle 1 , Anna Köhler 1 , Ralf Moos 3 , Eva M. Herzig 2 , Fabian Panzer 1
Affiliation  

In recent years, record efficiencies of halide perovskite-based devices have been achieved by processing high-quality thin films, where small morphology differences seem to be relevant for optimized optoelectronic functionality. However, a detailed understanding on how small morphological changes in perovskite films affect their structural and optoelectronic properties is still missing. Here, we investigate the influence of small morphology differences (i.e., increased grain size and crystallographic orientation), which are induced by hot-pressing methylammonium lead iodide (MAPbI3) thin films, on the structural properties, phase transition behavior, energetic disorder, and defects. To this end, detailed temperature-dependent photoluminescence (PL) and absorption analyses from 300 K down to 5 K are performed. The morphology differences, confirmed by scanning electron microscopy and X-ray diffractometry analyses, result in an increased phase transition temperature for hot-pressed (HP) films, which we attribute to less strain. Moreover, fluence-dependent and transient PL measurements reveal a lower defect density in HP films. Here, besides grain size, also the degree of orientation appears to enhance the charge carrier lifetimes. The identified interdependence of strain and defect properties with film morphology suggests small differences in the perovskite’s energetic disorder. Our work thus emphasizes the importance that even small structural differences in halide perovskites have on their optoelectronic functionality, spurring their further optimization.

中文翻译:

MAPbI3 薄膜中的取向和晶粒尺寸:对相变、无序和缺陷的影响

近年来,通过加工高质量的薄膜,卤化物钙钛矿基器件的效率达到了创纪录的水平,其中微小的形态差异似乎与优化的光电功能有关。然而,仍然缺乏对钙钛矿薄膜微小形态变化如何影响其结构和光电特性的详细了解。在这里,我们研究了由热压甲基铵碘化铅 (MAPbI 3) 引起的微小形态差异(即增加的晶粒尺寸和晶体取向)的影响) 薄膜,关于结构特性、相变行为、能量无序和缺陷。为此,进行了从 300 K 到 5 K 的详细温度依赖性光致发光 (PL) 和吸收分析。通过扫描电子显微镜和 X 射线衍射分析证实的形态差异导致热压 (HP) 薄膜的相变温度升高,我们将其归因于较小的应变。此外,依赖于注量的瞬态 PL 测量显示 HP 薄膜中的缺陷密度较低。在这里,除了晶粒尺寸外,取向度似乎也可以提高电荷载流子的寿命。已确定的应变和缺陷特性与薄膜形态的相互依赖性表明钙钛矿的能量紊乱存在微小差异。
更新日期:2023-05-30
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