Steele Julian A, Solano Eduardo, Jin Handong, Prakasam Vittal, Braeckevelt Tom, Yuan Haifeng, Lin Zhenni, de Kloe René, Wang Qiong, Rogge Sven M J, Van Speybroeck Veronique, Chernyshov Dmitry, Hofkens Johan, Roeffaers Maarten B J
cMACS, Department of Microbial and Molecular Systems, KU Leuven, Leuven, 3001, Belgium.
NCD-SWEET Beamline, ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona, 08290, Spain.
Adv Mater. 2021 Apr;33(13):e2007224. doi: 10.1002/adma.202007224. Epub 2021 Feb 26.
Controlling grain orientations within polycrystalline all-inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits; however, the forces governing texture formation are ambiguous. Using synchrotron X-ray diffraction, mesostructure formation within polycrystalline CsPbI Br powders as they cool from a high-temperature cubic perovskite (α-phase) is reported. Tetragonal distortions (β-phase) trigger preferential crystallographic alignment within polycrystalline ensembles, a feature that is suggested here to be coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic (γ-phase) CsPbI Br perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; i) I-rich films possess orthorhombic-like texture (<100> out-of-plane; <010> and <001> in-plane), while ii) Br-rich films form tetragonal-like texture (<110> out-of-plane; <110> and <001> in-plane). In contrast to relatively uninfluential factors like the choice of substrate, film thickness, and annealing temperature, Br incorporation modifies the γ-CsPbI Br crystal structure by reducing the orthorhombic lattice distortion (making it more tetragonal-like) and governs the formation of the different, energetically favored textures within polycrystalline thin films.
控制多晶全无机卤化物钙钛矿太阳能电池中的晶粒取向有助于提高其转换效率，使其接近热力学极限；然而，控制织构形成的力尚不明确。本文利用同步辐射X射线衍射技术，报道了多晶CsPbIBr粉末从高温立方钙钛矿（α相）冷却过程中的介观结构形成。四方畸变（β相）在多晶集合体中引发优先的晶体学取向排列，本文认为这一特征是通过界面力在多个相邻晶粒间协同作用，从而选择某些晶格畸变而非其他畸变。然后通过衬底夹持对正交晶系（γ相）CsPbIBr钙钛矿多晶薄膜施加外部各向异性，揭示了两种基本的单轴织构形成；i）富碘薄膜具有类似正交晶系的织构（<100>面外；<010>和<001>面内），而ii）富溴薄膜形成类似四方晶系的织构（<110>面外；<110>和<001>面内）。与诸如衬底选择、薄膜厚度和退火温度等相对影响较小的因素不同，溴的掺入通过减少正交晶格畸变（使其更类似四方晶系）来改变γ-CsPbIBr晶体结构，并控制多晶薄膜中不同的、能量上更有利的织构的形成。
