Alosaimi Ghaida, Huang Chien-Yu, Sharma Pankaj, Wu Tom, Seidel Jan
Department of Chemistry, Faculty of Science, Taif University, Taif, 21944, Saudi Arabia.
School of Materials Science and Engineering, UNSW Australia, Sydney, NSW, 2052, Australia.
Small. 2023 May;19(20):e2207220. doi: 10.1002/smll.202207220. Epub 2023 Feb 20.
Exceptional electronic, optoelectronic, and sensing properties of inorganic Cs-based perovskites are significantly influenced by the defect chemistry of the material. Although organic halide perovskites that have a polycrystalline structure are heavily studied, understanding of the defect properties at the grain boundaries (GB) of inorganic Cs-based perovskite quantum dots (QDs) is still limited. Here, morphology-dependent charge carrier dynamics of CsPbBr quantum dots at the nanoscale by performing scanning probe microscopy of thermally treated samples are investigated. The grain boundaries of defect-engineered samples show higher surface potential than the grain interiors under light illumination, suggesting an effective role of GBs as charge collection and transport channels. The lower density of crystallographic defects and lower trap density at GBs specifically of heat-treated samples cause insignificant dark current, lower local current hysteresis, and higher photocurrent, than the control samples. It is also shown that the decay rate of surface photovoltage of the heated sample is quicker than the control sample, which implies a considerable impact of ion migration on the relaxation dynamic of photogenerated charge carriers. These findings reveal that the annealing process is an effective strategy to control not only the morphology but also the optoelectrical properties of GB defects, and the dynamic of ion migration. Understanding the origin of photoelectric activity in this material allows for designing and engineering optoelectronic QD devices with enhanced functionality.
无机铯基钙钛矿优异的电子、光电和传感特性受到材料缺陷化学的显著影响。尽管具有多晶结构的有机卤化物钙钛矿得到了广泛研究，但对无机铯基钙钛矿量子点（QD）晶界（GB）处的缺陷特性的了解仍然有限。在此，通过对热处理样品进行扫描探针显微镜研究了纳米尺度下CsPbBr量子点的形貌依赖性电荷载流子动力学。在光照下，缺陷工程样品的晶界显示出比晶粒内部更高的表面电势，这表明晶界作为电荷收集和传输通道发挥了有效作用。与对照样品相比，经过热处理的样品在晶界处具有更低的晶体缺陷密度和更低的陷阱密度，导致暗电流不显著、局部电流滞后更低且光电流更高。还表明加热样品的表面光电压衰减速率比对照样品更快，这意味着离子迁移对光生电荷载流子的弛豫动力学有相当大的影响。这些发现表明，退火过程不仅是控制晶界缺陷的形貌和光电特性，以及离子迁移动力学的有效策略。了解这种材料中光电活性的起源有助于设计和制造具有增强功能的光电量子点器件。
