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Molecular Insights into Early Nuclei and Interfacial Mismatch during Vapor Deposition of Hybrid Perovskites on Titanium Dioxide Substrate
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2017-11-07 00:00:00 , DOI: 10.1021/acs.cgd.7b00626 Jingfan Wang 1 , Lingling Zhao 1 , Mingchao Wang 2 , Shangchao Lin 2
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2017-11-07 00:00:00 , DOI: 10.1021/acs.cgd.7b00626 Jingfan Wang 1 , Lingling Zhao 1 , Mingchao Wang 2 , Shangchao Lin 2
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Theoretical understanding of the nucleus structures of hybrid perovskites, such as those of the prototypical methylammonium lead triiodide (MAPbI3), can greatly improve the deposited thin film quality and the resulting optoelectronic device performance. In this paper, we report a systematic molecular dynamics simulation study on nucleation and interfacial mismatch during the vapor deposition of MAPbI3 on the TiO2 substrate under different ionic precursor (PbI2 and MAI salts) compositions and temperatures. Despite significant anisotropic lattice mismatches, small defects are observed at the TiO2/[MAI]0 interface due to intermediate electrostatic attractions between I and Ti atoms, while very strong electrostatic attractions between Pb and O atoms lead to significant defects at the TiO2/[PbI2]0 interface. From the vapor deposition simulations, we identify PbI42– tetrahedra, PbI53– pyramids, and PbI64– octahedra as dominant polyhedral building blocks of early MAPbI3 nuclei. Specifically, the PbI53– pyramids dominate over other polyhedra and could be a good candidate for converting into PbI64– octahedra upon further crystallization. We further identify early MAPbI3 nuclei built upon well-connected PbIx polyhedral clusters and finally locate the efficient early MAPbI3 nuclei based on sufficient amounts of surrounding MA+ cations. The populations of these early nuclei increase rapidly with increasing the MAI composition, suggesting that potential improvements in film quality could be introduced by depositing more MAI salts or MA+ cations, a finding consistent with experiments. Although the impact from temperature is weaker than that from composition, the optimal temperature for nucleation is found to decrease with increasing the precursor composition PbI2/MAI. Finally, the TiO2 substrate leads to layered structures of ionic species close to its surface, but such ordering does not seem to promote prenucleation, which poses a need for the new design of substrates that are more compatible with PbI64–-based early nuclei.
中文翻译：
钛钙钛矿上混合钙钛矿的气相沉积过程中的早期核和界面失配的分子洞察力。
从理论上了解杂化钙钛矿的核结构，例如典型的甲基碘化三碘化铅（MAPbI 3）的核结构，可以极大地改善沉积的薄膜质量并提高光电器件的性能。在本文中，我们报告了在不同离子前体（PbI 2和MAI盐）组成和温度下，MAPbI 3在TiO 2衬底上气相沉积过程中成核和界面失配的系统分子动力学模拟研究。尽管存在明显的各向异性晶格失配，但在TiO 2 / [MAI] 0处仍观察到小的缺陷由于在I和Ti原子之间存在中间的静电引力，因此界面形成了介电常数，而Pb和O原子之间的非常强的静电引力导致了TiO 2 / [PbI 2 ] 0界面处的明显缺陷。从气相沉积模拟中，我们确定PbI 4 2 –四面体，PbI 5 3 –金字塔和PbI 6 4 –八面体是早期MAPbI 3核的主要多面体结构单元。具体来说，PbI 5 3–金字塔比其他多面体更占优势，并且可能是转换为PbI 6 4–八面体进一步结晶。我们进一步确定早期MAPbI 3个晶核在连接良好的碘化铅内置X多面体簇和终于找到有效的及早MAPbI 3个基于足够量的周围MA细胞核+阳离子。这些早期核的种群随着MAI组成的增加而迅速增加，这表明可以通过沉积更多的MAI盐或MA +阳离子来引入潜在的膜质量改善，这一发现与实验相符。尽管温度的影响比组成的影响要弱，但发现成核的最佳温度随前体组成PbI 2的增加而降低。/ MAI。最后，TiO 2基材导致靠近其表面的离子种类的分层结构，但是这种有序性似乎并不能促进预成核，这就需要对与早期基于PbI 6 4的基材更兼容的新型基材进行设计。核。
更新日期：2017-11-08
中文翻译：
钛钙钛矿上混合钙钛矿的气相沉积过程中的早期核和界面失配的分子洞察力。
从理论上了解杂化钙钛矿的核结构，例如典型的甲基碘化三碘化铅（MAPbI 3）的核结构，可以极大地改善沉积的薄膜质量并提高光电器件的性能。在本文中，我们报告了在不同离子前体（PbI 2和MAI盐）组成和温度下，MAPbI 3在TiO 2衬底上气相沉积过程中成核和界面失配的系统分子动力学模拟研究。尽管存在明显的各向异性晶格失配，但在TiO 2 / [MAI] 0处仍观察到小的缺陷由于在I和Ti原子之间存在中间的静电引力，因此界面形成了介电常数，而Pb和O原子之间的非常强的静电引力导致了TiO 2 / [PbI 2 ] 0界面处的明显缺陷。从气相沉积模拟中，我们确定PbI 4 2 –四面体，PbI 5 3 –金字塔和PbI 6 4 –八面体是早期MAPbI 3核的主要多面体结构单元。具体来说，PbI 5 3–金字塔比其他多面体更占优势，并且可能是转换为PbI 6 4–八面体进一步结晶。我们进一步确定早期MAPbI 3个晶核在连接良好的碘化铅内置X多面体簇和终于找到有效的及早MAPbI 3个基于足够量的周围MA细胞核+阳离子。这些早期核的种群随着MAI组成的增加而迅速增加，这表明可以通过沉积更多的MAI盐或MA +阳离子来引入潜在的膜质量改善，这一发现与实验相符。尽管温度的影响比组成的影响要弱，但发现成核的最佳温度随前体组成PbI 2的增加而降低。/ MAI。最后，TiO 2基材导致靠近其表面的离子种类的分层结构，但是这种有序性似乎并不能促进预成核，这就需要对与早期基于PbI 6 4的基材更兼容的新型基材进行设计。核。
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