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Cooperative B-site octahedral tilting, distortion and A-site conformational change induced phase transitions of a 2D lead halide perovskite
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2021-08-25 , DOI: 10.1039/d1qm00566a Muhammad Azeem 1 , Yan Qin 2 , Zhi-Gang Li 1 , Wei Li 1
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2021-08-25 , DOI: 10.1039/d1qm00566a Muhammad Azeem 1 , Yan Qin 2 , Zhi-Gang Li 1 , Wei Li 1
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Hybrid organic–inorganic perovskites (HOIPs) can undergo diverse phase transitions which give rise to desirable properties such as ferroelectricity and piezoelectricity. Hitherto, the origin of their phase transitions is primarily due to the order–disorder of the organic component while other driving forces remain largely unexplored. In this study, the high-pressure structural evolution of a 2D hybrid lead halide perovskite, [(BA)2PbI4] (BA = benzylammonium), was investigated which reveals that its orthorhombic to triclinic transition is driven by the cooperative PbI6 octahedral tilting, distortion and conformational change of the BA amine cation. Density functional theory calculations demonstrate that [PbI6]4− octahedra slightly tilt and distort to result in overall decreased Pb–I bond lengths and Pb–I–Pb angles but increased I–Pb–I angles, while the BA cation slightly rotates towards its benzene ring across the transition. Moreover, the photoluminescence emission exhibits a red-shift along with the decrease in intensity which could be attributed to the contraction of Pb–I bonds and flattening of Pb–I–Pb bond angles under pressure. Our findings demonstrate that the degree of freedom of the inorganic framework also plays a key role in driving the phase transitions of 2D HOIPs, which needs to be taken into account in investigating symmetry-breaking properties of this emerging class of electronic materials.
中文翻译：
二维卤化铅钙钛矿的协同 B 位八面体倾斜、畸变和 A 位构象变化引起的相变
混合有机-无机钙钛矿（HOIPs）可以经历不同的相变，从而产生所需的性能，如铁电性和压电性。迄今为止，它们相变的起源主要是由于有机成分的有序-无序，而其他驱动力在很大程度上仍未得到探索。在这项研究中，研究了二维杂化卤化铅钙钛矿 [(BA) 2 PbI 4 ]（BA = 苄基铵）的高压结构演化，这表明其正交到三斜晶相的转变是由协同 PbI 6八面体驱动的BA 胺阳离子的倾斜、扭曲和构象变化。密度泛函理论计算表明 [PbI 6 ] 4−八面体略微倾斜和扭曲，导致 Pb-I 键长和 Pb-I-Pb 角整体减少，但 I-Pb-I 角增加，而 BA 阳离子在过渡时略微向苯环方向旋转。此外，光致发光随着强度的降低而发生红移，这可能归因于压力下 Pb-I 键的收缩和 Pb-I-Pb 键角的变平。我们的研究结果表明，无机骨架的自由度在推动 2D HOIP 的相变方面也起着关键作用，在研究这类新兴电子材料的对称破坏特性时需要考虑到这一点。
更新日期：2021-09-14
中文翻译：
二维卤化铅钙钛矿的协同 B 位八面体倾斜、畸变和 A 位构象变化引起的相变
混合有机-无机钙钛矿（HOIPs）可以经历不同的相变，从而产生所需的性能，如铁电性和压电性。迄今为止，它们相变的起源主要是由于有机成分的有序-无序，而其他驱动力在很大程度上仍未得到探索。在这项研究中，研究了二维杂化卤化铅钙钛矿 [(BA) 2 PbI 4 ]（BA = 苄基铵）的高压结构演化，这表明其正交到三斜晶相的转变是由协同 PbI 6八面体驱动的BA 胺阳离子的倾斜、扭曲和构象变化。密度泛函理论计算表明 [PbI 6 ] 4−八面体略微倾斜和扭曲，导致 Pb-I 键长和 Pb-I-Pb 角整体减少，但 I-Pb-I 角增加，而 BA 阳离子在过渡时略微向苯环方向旋转。此外，光致发光随着强度的降低而发生红移，这可能归因于压力下 Pb-I 键的收缩和 Pb-I-Pb 键角的变平。我们的研究结果表明，无机骨架的自由度在推动 2D HOIP 的相变方面也起着关键作用，在研究这类新兴电子材料的对称破坏特性时需要考虑到这一点。
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