Polishchuk Serhii, Puppin Michele, Crepaldi Alberto, Gatti Gianmarco, Dirin Dmitry N, Nazarenko Olga, Colonna Nicola, Marzari Nicola, Kovalenko Maksym V, Grioni Marco, Chergui Majed
Laboratoire de Spectroscopie Ultrarapide (LSU) and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC, 1015 Lausanne, Switzerland.
Institute of Physics and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Nano Lett. 2022 Feb 9;22(3):1067-1074. doi: 10.1021/acs.nanolett.1c03941. Epub 2022 Jan 19.
Describing the nanoscale charge carrier transport at surfaces and interfaces is fundamental for designing high-performance optoelectronic devices. To achieve this, we employ time- and angle-resolved photoelectron spectroscopy with ultraviolet pump and extreme ultraviolet probe pulses. The resulting high surface sensitivity reveals an ultrafast carrier population decay associated with surface-to-bulk transport, which was tracked with a sub-nanometer spatial resolution normal to the surface, and on a femtosecond time scale, in the case of the inorganic CsPbBr lead halide perovskite. The decay time exhibits a pronounced carrier density dependence, which is attributed via modeling to enhanced diffusive transport and concurrent recombination. The transport is found to approach an ordinary diffusive regime, limited by electron-hole scattering, at the highest excitation fluences. This approach constitutes an important milestone in our capability to probe hot-carrier transport at solid interfaces with sub-nanometer resolution in a theoretically and experimentally challenging, yet technologically relevant, high-carrier-density regime.
描述表面和界面处的纳米级电荷载流子传输对于设计高性能光电器件至关重要。为了实现这一点，我们采用了具有紫外泵浦和极紫外探测脉冲的时间分辨和角分辨光电子能谱。由此产生的高表面灵敏度揭示了与表面到体相传输相关的超快载流子布居衰减，在无机CsPbBr卤化铅钙钛矿的情况下，这种衰减在垂直于表面的亚纳米空间分辨率下以及飞秒时间尺度上被跟踪。衰减时间表现出明显的载流子密度依赖性，通过建模将其归因于增强的扩散传输和并发复合。在最高激发通量下，发现传输接近由电子-空穴散射限制的普通扩散 regime。这种方法是我们在理论和实验上具有挑战性但在技术上相关的高载流子密度 regime 中以亚纳米分辨率探测固体界面处热载流子传输能力的一个重要里程碑。
