Nano Lett. 2018 Oct 10;18(10):6271-6278. doi: 10.1021/acs.nanolett.8b02417. Epub 2018 Sep 18.
Metal halide perovskite thin films have achieved remarkable performance in optoelectronic devices but suffer from spatial heterogeneity in their electronic properties. To achieve higher device performance and reliability needed for widespread commercial deployment, spatial heterogeneity of optoelectronic properties in the perovskite thin film needs to be understood and controlled. Clear identification of the causes underlying this heterogeneity, most importantly the spatial heterogeneity in charge trapping behavior, has remained elusive. Here, a multimodal imaging approach consisting of photoluminescence, optical transmission, and atomic force microscopy is utilized to separate electronic heterogeneity from morphology variations in perovskite thin films. By comparing the degree of heterogeneity in highly oriented and randomly oriented polycrystalline perovskite thin film samples, we reveal that disorders in the crystallographic orientation of the grains play a dominant role in determining charge trapping and electronic heterogeneity. This work also demonstrates a polycrystalline thin film with uniform charge trapping behavior by minimizing crystallographic orientation disorder. These results suggest that single crystals may not be required for perovskite thin film based optoelectronic devices to reach their full potential.
金属卤化物钙钛矿薄膜在光电设备中表现出显著的性能，但在电子性质方面存在空间异质性。为了实现广泛商业应用所需的更高的器件性能和可靠性，需要了解和控制钙钛矿薄膜中光电性质的空间异质性。明确识别导致这种异质性的原因，尤其是电荷俘获行为的空间异质性，仍然难以捉摸。在这里，利用包含光致发光、光透射和原子力显微镜的多模态成像方法，将电子异质性与钙钛矿薄膜的形貌变化分离。通过比较高度取向和随机取向多晶钙钛矿薄膜样品的异质程度，我们揭示了晶粒的晶向无序在决定电荷俘获和电子异质性方面起着主导作用。这项工作还通过最小化晶向无序，展示了具有均匀电荷俘获行为的多晶薄膜。这些结果表明，对于基于钙钛矿薄膜的光电设备，达到其全部潜力可能并不需要单晶。
