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Iodide vs Chloride: The Impact of Different Lead Halides on the Solution Chemistry of Perovskite Precursors
ACS Applied Energy Materials ( IF 6.4 ) Pub Date : 2021-09-13 , DOI: 10.1021/acsaem.1c01874
Waldemar Kaiser 1 , Eros Radicchi 1, 2 , Edoardo Mosconi 1 , Ali Kachmar 1 , Filippo De Angelis 2, 3, 4
Affiliation  

Controlled perovskite growth from solution is crucial for efficient optoelectronic applications and requires a deep understanding of the perovskite precursor chemistry. The so-called “chlorine route” to lead–iodide perovskite, using PbCl2 or MACl additive as a precursor, is frequently employed to form homogeneous perovskite layers by retarding perovskite crystallization. To understand the role of chlorine-containing lead precursors in solution, we analyze the chemical interaction of PbCl2 and PbI2 precursors with commonly employed solvents (γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)) by combining first-principles simulations and experimental UV–vis spectroscopy in diluted precursor solutions. Ab initio molecular dynamics simulations reveal reduced solvation and an increased free energy barrier of lead-halide bond dissociation of PbCl2 compared to PbI2 with chlorine acting as a stronger ligand, which, in turn, limits the solvent coordination. In contrast to PbI2, PbCl2 absorption spectra lack signatures of high-valent [PbCln]2–n complexes and show low sensitivity on the employed solvent, as confirmed by combined UV–vis and excited-state time-dependent density functional theory (TD-DFT) analysis. Altogether, our data suggest the presence of residual chlorine coordinated to Pb even in the presence of high iodine excess, which may retard the perovskite growth and could also lead to chlorine incorporation within the lead–iodide perovskite crystal.

中文翻译:

碘化物与氯化物:不同卤化铅对钙钛矿前驱体溶液化学的影响

溶液中钙钛矿的受控生长对于高效的光电应用至关重要,并且需要对钙钛矿前体化学有深入的了解。使用 PbCl 2或 MACl 添加剂作为前体的所谓的“氯路线”到碘化铅钙钛矿,经常被用来通过延缓钙钛矿结晶来形成均匀的钙钛矿层。为了了解含氯铅前体在溶液中的作用,我们分析了 PbCl 2和 PbI 2前体与常用溶剂(γ-丁内酯 (GBL)、NN-二甲基甲酰胺 (DMF) 和二甲基亚砜 (DMSO)),通过在稀释的前体溶液中结合第一性原理模拟和实验紫外-可见光谱。从头计算分子动力学模拟显示减少溶剂化和增加的PBCL的铅卤化物键离解的自由能屏障2相比碘化铅2与充当较强的配体,其反过来又限制了溶剂协调氯。与 PbI 2 相比,PbCl 2吸收光谱缺乏高价 [PbCl n ] 2– n 的特征复合物并对所使用的溶剂显示出低灵敏度,这通过组合 UV-vis 和激发态时间相关密度泛函理论 (TD-DFT) 分析证实。总而言之,我们的数据表明,即使在碘过量的情况下,残留的氯也会与铅配位,这可能会阻碍钙钛矿的生长,也可能导致氯掺入碘化铅钙钛矿晶体中。
更新日期:2021-09-27
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