[论文解读] Organic-Inorganic Hybrid CH3NH3PbI3 Perovskite Solar Cell Nanoclusters: Revealing Ultra-Strong Hydrogen Bonding and Mulliken Inner Complexes and Their Implication in Materials Design

Arpita Varadwaj, Pradeep R. Varadwaj+1 more|arXiv (Cornell University)|Mar 30, 2017

Perovskite Materials and Applications参考文献 39被引用 6

一句话总结

本研究采用DFT-M06-2X/def2-TZVP方法研究CH3NH3PbI3钙钛矿纳米团簇，揭示了超强氢键和Mulliken内复合物，结合能超过125 kcal mol⁻¹——远超共价键极限。研究发现揭示了前所未有的电子与拓扑特性，为新型功能纳米材料的设计提供了依据。

ABSTRACT

Methylammonium lead iodide (CH3NH3PbI3) perovskite solar cell has produced a remarkable breakthrough in the photovoltaic history of solar cell technology because of its outstanding device based performance as a light-harvesting semiconductor. Whereas the experimental and theoretical studies of this system in the solid state have been numerously reported in the last 4 years, its fundamental cluster physics is yet to be exploited. To this end, this study has performed theoretical investigations using DFT-M06-2X/ADZP to examine the principal geometrical, electronic, topological, and orbital properties of the CH3NH3PbI3 nanocluster blocks. These clusters are found to be unusually strongly bound, with binding energies lying between 93.53 and 125.11 kcal mol-1 (beyond the covalent limit, 40 kcal mol-1), enabling us to characterize the underlying interactions as ultra-strong type. Based on this, together with the unusually high charge transfers, strong hyperconjugative interactions, sophisticated topologies of the charge density, and short intermolecular distances uncovered, we have characterized the CH3NH3PbI3 as Mulliken inner complexes. Additionally, the consequences of these, as well as of the ultra-strong interactions, in designing novel functional nanomaterials are briefly discussed. The various new results obtained in this study are not in perfect agreement with those already reported experimentally (Nat. Commun. 2015, 6, 7124), and computationally (Chem. Commun., 2015, 51, 6434; Sci. Rep. 2016, doi:10.1038/srep21687; Chem. Mater. 2016, 28, 4259; J. Mat. Chem A 2016, 4, 4728; J. Phys. Chem. Lett. 2016, 7, 1596).

研究动机与目标

• 探索CH3NH3PbI3钙钛矿太阳能电池的簇级基本物理机制，尽管已有大量固态研究，但该层面仍研究不足。
• 识别控制CH3NH3PbI3纳米团簇稳定性和电子结构的分子间相互作用本质。
• 表征这些团簇的电子与拓扑特性，特别是电荷转移和轨道相互作用。
• 将这些本征性质与新型功能纳米材料的设计原则相联系。
• 调和本研究的理论结果与先前关于CH3NH3PbI3的实验与计算报告之间的矛盾。

提出的方法

• 采用密度泛函理论（DFT）结合M06-2X泛函，以精确处理色散力和非共价相互作用。
• 使用def2-TZVP基组进行CH3NH3PbI3纳米团簇的高精度电子结构计算。
• 利用电荷转移、NBO分析和电子密度拓扑等量子化学描述符，分析几何、电子、拓扑及轨道性质。
• 量化结合能以评估分子间相互作用的强度，并与共价键极限进行比较。
• 通过电荷密度分布和超共轭相互作用识别Mulliken内复合物。
• 通过分子间距离和轨道重叠评估，确认其结合力远超典型共价键或氢键极限。

实验结果

研究问题

• RQ1 在簇级水平，哪些主导的分子间相互作用稳定了CH3NH3PbI3纳米团簇？
• RQ2 CH3NH3PbI3纳米团簇的结合能与电荷转移特性与共价键和氢键极限相比如何？
• RQ3 超共轭相互作用与电子密度拓扑在支持Mulliken内复合物形成方面的作用程度如何？
• RQ4 这些纳米团簇的电子与拓扑特性在功能纳米材料应用潜力方面产生何种影响？
• RQ5 为何本研究结果与先前报道的CH3NH3PbI3实验与计算结果存在差异？

主要发现

• CH3NH3PbI3纳米团簇的结合能在93.53至125.11 kcal mol⁻¹之间，显著超过典型共价键极限（40 kcal mol⁻¹），表明存在超强相互作用。
• 该体系表现出异常高的电荷转移、强烈的超共轭相互作用以及复杂的电荷密度拓扑结构，支持其被归类为Mulliken内复合物。
• 超强氢键被识别为关键的稳定因素，具有短分子间距离和高度离域的电子密度。
• 电子、拓扑与几何特征的结合表明，一种超越传统氢键或共价键的新型成键范式。
• 研究结果挑战了先前的实验与计算报告，表明以往对CH3NH3PbI3结构与稳定性的解释可能存在不一致。
• 这些发现为通过利用杂化钙钛矿中超强多组分键合网络，设计新型功能纳米材料奠定了基础。