Kamminga Machteld E, de Wijs Gilles A, Havenith Remco W A, Blake Graeme R, Palstra Thomas T M
Radboud University , Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
Ghent Quantum Chemistry Group, Department of Inorganic and Physical Chemistry, Ghent University , Krijgslaan 281 (S33), B-9000 Gent, Belgium.
Inorg Chem. 2017 Jul 17;56(14):8408-8414. doi: 10.1021/acs.inorgchem.7b01096. Epub 2017 Jul 5.
We use a layered solution crystal growth method to synthesize high-quality single crystals of two different benzylammonium lead iodide perovskite-like organic/inorganic hybrids. The well-known (CHCHNH)PbI phase is obtained in the form of bright orange platelets, with a structure comprised of single ⟨100⟩-terminated sheets of corner-sharing PbI octahedra separated by bilayers of the organic cations. The presence of water during synthesis leads to formation of a novel minority phase that crystallizes in the form of nearly transparent, light yellow bar-shaped crystals. This phase adopts the monoclinic space group P2/n and incorporates water molecules, with structural formula (CHCHNH)PbI·2HO. The crystal structure consists of ribbons of edge-sharing PbI octahedra separated by the organic cations. Density functional theory calculations including spin-orbit coupling show that these edge-sharing PbI octahedra cause the band gap to increase with respect to corner-sharing PbI octahedra in (CHCHNH)PbI. To gain systematic insight, we model the effect of the connectivity of PbI octahedra on the band gap in idealized lead iodide perovskite-derived compounds. We find that increasing the connectivity from corner-, via edge-, to face-sharing causes a significant increase in the band gap. This provides a new mechanism to tailor the optical properties in organic/inorganic hybrid compounds.
我们采用分层溶液晶体生长法合成了两种不同的苄基铵碘化铅钙钛矿型有机/无机杂化物的高质量单晶。众所周知的(CH₃CH₂NH₃)PbI₃相以亮橙色片状形式获得，其结构由由有机阳离子双层分隔的角共享PbI₆八面体的单个⟨100⟩端接片组成。合成过程中水分的存在导致形成一种新型的少数相，其以近乎透明的浅黄色棒状晶体形式结晶。该相采用单斜空间群P2/n并包含水分子，化学式为(CH₃CH₂NH₃)PbI₃·2H₂O。晶体结构由被有机阳离子分隔的边共享PbI₆八面体的条带组成。包括自旋轨道耦合的密度泛函理论计算表明，这些边共享PbI₆八面体导致带隙相对于(CH₃CH₂NH₃)PbI₃中的角共享PbI₆八面体增大。为了获得系统的见解，我们对理想的碘化铅钙钛矿衍生化合物中PbI₆八面体的连接性对带隙的影响进行了建模。我们发现，从角共享、经边共享到面共享增加连接性会导致带隙显著增加。这为调整有机/无机杂化化合物的光学性质提供了一种新机制。
