We use correlated confocal and wide-field fluorescence microscopy to probe the interplay between local variations in charge carrier recombination and charge carrier transport in methylammonium lead triiodide perovskite thin films. We find that local photoluminescence variations present in confocal imaging are also observed in wide-field imaging, while intensity-dependent confocal measurements show that the heterogeneity in nonradiative losses observed at low excitation powers becomes less pronounced at higher excitation powers. Both confocal and wide-field images show that carriers undergo anisotropic diffusion due to differences in intergrain connectivity. These data are all qualitatively consistent with trap-dominated variations in local photoluminescence intensity and with grain boundaries that exhibit varying degrees of opacity to carrier transport. We use a two-dimensional kinetic model to simulate and compare confocal time-resolved photoluminescence decay traces with experimental data. The simulations further support the assignment of local variations in nonradiative recombination as the primary cause of photoluminescence heterogeneity in the films studied herein. These results point to surface passivation and intergrain connectivity as areas that could yield improvements in perovskite solar cells and optoelectronic device performance.

中文翻译：

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跟踪混合钙钛矿半导体中的光激发载流子：陷阱主导的空间异质性和扩散

我们使用相关的共聚焦和宽视野荧光显微镜来探测在甲基铵三碘化铅钙钛矿薄膜中电荷载流子重组和电荷载流子传输的局部变化之间的相互作用。我们发现在共聚焦成像中也存在局部光致发光变化，而在宽场成像中也观察到了，而强度相关的共聚焦测量表明，在低激发功率下观察到的非辐射损耗的不均匀性在较高激发功率下变得不那么明显。共焦和宽视场图像均显示，由于晶粒间连通性的差异，载流子经历了各向异性扩散。这些数据在质量上均与陷阱占主导的局部光致发光强度变化以及晶界对载流子迁移的不透明程度一致。我们使用二维动力学模型来模拟和比较共聚焦时间分辨的光致发光衰减迹线与实验数据。模拟进一步支持将非辐射复合中的局部变化指定为本文研究的膜中光致发光异质性的主要原因。这些结果表明表面钝化和晶间连接性是可以改善钙钛矿太阳能电池和光电器件性能的领域。模拟进一步支持将非辐射复合中的局部变化指定为本文研究的膜中光致发光异质性的主要原因。这些结果表明表面钝化和晶间连接性是可以改善钙钛矿太阳能电池和光电器件性能的领域。模拟进一步支持将非辐射复合中的局部变化指定为本文研究的膜中光致发光异质性的主要原因。这些结果表明表面钝化和晶间连接性是可以改善钙钛矿太阳能电池和光电器件性能的领域。