Hidalgo Juanita, An Yu, Yehorova Dariia, Li Ruipeng, Breternitz Joachim, Perini Carlo A R, Hoell Armin, Boix Pablo P, Schorr Susan, Kretchmer Joshua S, Correa-Baena Juan-Pablo
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
Chem Mater. 2023 May 25;35(11):4181-4191. doi: 10.1021/acs.chemmater.3c00075. eCollection 2023 Jun 13.
Preferred crystallographic orientation in polycrystalline films is desirable for efficient charge carrier transport in metal halide perovskites and semiconductors. However, the mechanisms that determine the preferred orientation of halide perovskites are still not well understood. In this work, we investigate crystallographic orientation in lead bromide perovskites. We show that the solvent of the precursor solution and organic A-site cation strongly affect the preferred orientation of the deposited perovskite thin films. Specifically, we show that the solvent, dimethylsulfoxide, influences the early stages of crystallization and induces preferred orientation in the deposited films by preventing colloidal particle interactions. Additionally, the methylammonium A-site cation induces a higher degree of preferred orientation than the formamidinium counterpart. We use density functional theory to show that the lower surface energy of the (100) plane facets in methylammonium-based perovskites, compared to the (110) planes, is the reason for the higher degree of preferred orientation. In contrast, the surface energy of the (100) and (110) facets is similar for formamidinium-based perovskites, leading to lower degree of preferred orientation. Furthermore, we show that different A-site cations do not significantly affect ion diffusion in bromine-based perovskite solar cells but impact ion density and accumulation, leading to increased hysteresis. Our work highlights the interplay between the solvent and organic A-site cation which determine crystallographic orientation and plays a critical role in the electronic properties and ionic migration of solar cells.
对于金属卤化物钙钛矿和半导体中高效的电荷载流子传输而言，多晶薄膜中择优的晶体取向是十分理想的。然而，决定卤化物钙钛矿择优取向的机制仍未得到充分理解。在这项工作中，我们研究了溴化铅钙钛矿中的晶体取向。我们发现前驱体溶液的溶剂和有机A位阳离子强烈影响沉积的钙钛矿薄膜的择优取向。具体而言，我们表明溶剂二甲基亚砜影响结晶的早期阶段，并通过防止胶体颗粒相互作用在沉积薄膜中诱导择优取向。此外，甲基铵A位阳离子比甲脒阳离子诱导出更高程度的择优取向。我们使用密度泛函理论表明，与(110)平面相比，甲基铵基钙钛矿中(100)平面小面的较低表面能是择优取向程度更高的原因。相比之下，甲脒基钙钛矿中(100)和(110)小面的表面能相似，导致择优取向程度较低。此外，我们表明不同的A位阳离子对基于溴的钙钛矿太阳能电池中的离子扩散没有显著影响，但会影响离子密度和积累，导致滞后现象增加。我们的工作突出了溶剂和有机A位阳离子之间的相互作用，它们决定了晶体取向，并在太阳能电池的电子特性和离子迁移中起着关键作用。
