The spin‐coating and subsequent low‐temperature annealing processes of organic/inorganic halide perovskites are investigated using in situ high‐speed spectral reflectance measurements. Methyl ammonium lead triiodide (CH₃NH₃PbI₃, MAPI), methyl ammonium lead tribromide (CH₃NH₃PbBr₃, MAPBr), formamidinium lead triiodide (HC(NH₂)₂PbI₃, FAPI), and triple cation‐based (TripleCat) perovskite Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃ are used as precursor solutions. After ≈1 s of spin coating, interference fringes develop that are used to determine the thickness of the layers. The spontaneous formation of MAPBr and TripleCat perovskite polycrystalline layers is observed during spin coating at room temperature. The phase transition from the other precursor solutions to the polycrystalline perovskite layers is monitored with diffuse reflectance measurements during the low‐temperature annealing step. These measurements permit the monitoring of the crystallization process that affects the bandgap of perovskites. Furthermore, it is possible to investigate the phase separation that occurs in perovskite mixtures during annealing by a second relative minimum in the reflectance spectra. The obtained results show that fast reflectance measurements are very useful to characterize kinetics and phase transition. Moreover, this fast experimental method provides insight into the formation of perovskite thin films and allows monitoring these processes on a timescale of some tens of milliseconds.

中文翻译：

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有机-无机钙钛矿前体溶液的旋涂和退火过程中的快速光学反射率测量

使用原位高速光谱反射率测量研究了有机/无机卤化物钙钛矿的旋涂和随后的低温退火工艺。甲基铵三碘化铅（CH ₃ NH ₃碘化铅₃，MAPI），甲基铵，三溴化铅（CH ₃ NH ₃ PbBr ₃，MAPBr），甲脒三碘化铅（HC（NH ₂）₂碘化铅₃，FAPI），和三阳离子基（TripleCat）钙钛矿Cs _0.05（FA _0.83 MA _0.17）_0.95 Pb（I _0.83 Br _0.17）₃用作前体溶液。旋涂≈1 s后，会产生干涉条纹，这些干涉条纹用于确定涂层的厚度。在室温下旋涂过程中观察到MAPBr和TripleCat钙钛矿多晶层的自发形成。在低温退火步骤中，通过漫反射测量可监控从其他前体溶液到多晶钙钛矿层的相变。这些测量结果可以监测影响钙钛矿带隙的结晶过程。此外，有可能通过反射光谱中的第二个相对最小值来研究在退火过程中钙钛矿混合物中发生的相分离。获得的结果表明，快速反射率测量对于表征动力学和相变非常有用。而且，这种快速的实验方法可以洞察钙钛矿薄膜的形成，并可以在数十毫秒的时间范围内监视这些过程。