Relevance of processing parameters for grain growth of metal halide perovskites with nanoimprint
Relevance of processing parameters for grain growth of metal halide perovskites with nanoimprint
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DOI：
10.1007/s00339-021-04830-0
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发表时间：
2021-08
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通讯作者：
A. Mayer;T. Haeger;M. Runkel;J. Rond;J. Staabs;F. van gen Hassend;A. Röttger;P. Görrn;T. Ried
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文献类型：
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作者：
A. Mayer;T. Haeger;M. Runkel;J. Rond;J. Staabs;F. van gen Hassend;A. Röttger;P. Görrn;T. Ried
由有机-无机钙钛矿的多晶层制备的器件的质量和稳定性高度依赖于主要的晶粒尺寸。在层制备期间或在后处理步骤中进行晶粒尺寸的调整。我们的研究是指热压印作为后处理步骤，以诱导钙钛矿层中的晶粒生长，提供为多层器件提供平坦表面的额外好处。所研究的材料是MAPbBr 3;我们研究了在100 bar压力和高达150 °C温度下的晶粒生长，在该温度范围内，加压冲压有利于避免热降解。晶粒粗化以自相似的方式发展，具有对数正态的晶粒尺寸分布;像“正常”或“二次”生长这样的类别不太适用，因为这些层在压印诱导的晶粒生长之前已经具有优先取向。用基于毛细管的生长定律模拟实验;实验确定相应的参数，活化能为Q = 0.3 eV。结果表明，对于压印，与晶粒生长相关的主要参数也是温度;为了在合理的处理时间内诱导MAPbBr 3中的晶粒生长，建议温度为120 °C及以上。压印过程中的机械状况的分析表明，热应力占主导地位。弹性能和表面能的最小化共同有利于MaPbBr 3层中具有（100）取向的晶粒的发展。此外，实验表明，用于层制备的材料的纯度是实现大晶粒的主要因素;然而，层的勤奋和始终相似的制备同样重要，因为它定义了所得钙钛矿层的纯度，与其生长能力密切相关。这些结果不仅有助于评估当选择特定温度和时间时层相对于晶粒生长的潜力;它们还有助于评估层在温度负载下的长期稳定性，例如在器件的操作期间。
The quality and the stability of devices prepared from polycrystalline layers of organic–inorganic perovskites highly depend on the grain sizes prevailing. Tuning of the grain size is either done during layer preparation or in a post-processing step. Our investigation refers to thermal imprint as the post-processing step to induce grain growth in perovskite layers, offering the additional benefit of providing a flat surface for multi-layer devices. The material studied is MAPbBr3; we investigate grain growth at a pressure of 100 bar and temperatures of up to 150 °C, a temperature range where the pressurized stamp is beneficial to avoid thermal degradation. Grain coarsening develops in a self-similar way, featuring a log-normal grain size distribution; categories like ‘normal’ or ‘secondary’ growth are less applicable as the layers feature a preferential orientation already before imprint-induced grain growth. The experiments are simulated with a capillary-based growth law; the respective parameters are determined experimentally, with an activation energy of Q ≈ 0.3 eV. It turns out that with imprint as well the main parameter relevant to grain growth is temperature; to induce grain growth in MAPbBr3within a reasonable processing time a temperature of 120 °C and beyond is advised. An analysis of the mechanical situation during imprint indicates a dominance of thermal stress. The minimization of elastic energy and surface energy together favours the development of grains with (100)-orientation in MaPbBr3layers. Furthermore, the experiments indicate that the purity of the materials used for layer preparation is a major factor to achieve large grains; however, a diligent and always similar preparation of the layer is equally important as it defines the pureness of the resulting perovskite layer, intimately connected with its capability to grow. The results are not only of interest to assess the potential of a layer with respect to grain growth when specific temperatures and times are chosen; they also help to rate the long-term stability of a layer under temperature loading, e.g. during the operation of a device.