Resolving Rotational Stacking Disorder and Electronic Level Alignment in a 2D Oligothiophene-Based Lead Iodide Perovskite
Resolving Rotational Stacking Disorder and Electronic Level Alignment in a 2D Oligothiophene-Based Lead Iodide Perovskite
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DOI：
10.1021/acs.chemmater.9b03208
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发表时间：
2019-10-22
影响因子：
8.6
通讯作者：
Mitzi, David B.
中科院分区：
文献类型：
--
作者：
Jana, Manoj K.;Liu, Chi;Mitzi, David B.
二维（2D）杂化有机-无机钙钛矿（HOIP）代表由交替的无机层和有机层组成的不同量子阱异质结构。虽然2D HOIP在X射线散射的三维中名义上是周期性的，但无机层可以准随机取向，导致旋转堆叠无序（RSD）。RSD表现为沿堆叠方向沿着的分辨差的扩散X射线散射，将结构描述限制为明显无序的亚电池。然而，局部有序偏好仍然可以存在于相邻的晶胞之间，并且可以显著地影响性质，特别是电子结构。在此，我们阐明了RSD并确定了2D [AE 2 T] PbI 4 HOIP（AE 2 T：5，5 '-双（乙基铵）-[2，2'-联噻吩]）中的优选局部排序。我们使用第一性原理计算来确定一组系统生成的具有不同顺序模式的超晶胞之间的能量差异。我们发现，层间有序的倾向是弱的，解释所观察到的RSD在不同的平面内旋转的PbI 6八面体在相邻的无机平面。相比之下，在给定的有机层内的排序偏好是强的，有利于相邻的AE 2 T阳离子的人字形排列。计算的近端有机和无机前沿轨道的价带电子水平对齐显着不同的AE 2 T阳离子的本地安排，只有最稳定的AE 2 T配置导致界面类型Ib带对齐与观察到的光学性质一致。本研究强调了解决当地的结构安排在2D HOIP可靠的结构性能预测的重要性。
Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) represent diverse quantum well heterostructures composed of alternating inorganic and organic layers. While 2D HOIPs are nominally periodic in three dimensions for X-ray scattering, the inorganic layers can orient quasi-randomly, leading to rotational stacking disorder (RSD). RSD manifests as poorly resolved, diffuse X-ray scattering along the stacking direction, limiting the structural description to an apparently disordered subcell. However, local ordering preferences can still exist between adjacent unit cells and can considerably impact the properties, particularly the electronic structure. Here, we elucidate RSD and determine the preferred local ordering in the 2D [AE2T]PbI4HOIP AE2T: 5,5'-bis(ethylammonium)-[2,2'-bithiophene]). We use first-principles calculations to determine energy differences between a set of systematically generated supercells with different order patterns. We show that interlayer ordering tendencies are weak, explaining the observed RSD in terms of differing in-plane rotation of PbI6 octahedra in neighboring inorganic planes. In contrast, the ordering preference within a given organic layer is strong, favoring a herringbone-type arrangement of adjacent AE2T cations. The calculated electronic level alignments of proximal organic and inorganic frontier orbitals in the valence band vary significantly with the local arrangement of AE2T cations; only the most stable AE2T configuration leads to an interfacial type-Ib band alignment consistent with observed optical properties. The present study underscores the importance of resolving local structure arrangements in 2D HOIPs for reliable structure-property prediction.