Feng Donghai, Yakovlev Dmitri R, Dubertret Benoit, Bayer Manfred
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany.
ACS Nano. 2020 Jun 23;14(6):7237-7244. doi: 10.1021/acsnano.0c02402. Epub 2020 May 29.
We investigate the charge separation dynamics provided by carrier surface trapping in CdSe/CdS core/shell nanoplatelets by means of a three-laser-beam pump-orientation-probe technique, detecting the electron spin coherence at room temperature. Signals with two Larmor precession frequencies are found, which strongly differ in their dynamical characteristics and dependencies on pump power and shell thickness. The electron trapping process occurs on a time scale of about 10 ns, and the charge separation induced thereby has a long lifetime of up to hundreds of microseconds. On the other hand, the hole trapping requires times from subpicoseconds to hundreds of picoseconds, and the induced charge separation has a lifetime of a few nanoseconds. With increasing CdS shell thickness the hole trapping vanishes, while the electron trapping is still detectable. These findings have important implications for understanding the photophysical processes of nanoplatelets and other colloidal nanostructures.
我们通过三激光束泵浦-取向-探测技术研究了CdSe/CdS核/壳纳米片层中载流子表面俘获所提供的电荷分离动力学，在室温下检测电子自旋相干性。发现了具有两个拉莫尔进动频率的信号，它们在动力学特性以及对泵浦功率和壳层厚度的依赖性方面有很大差异。电子俘获过程发生在大约10纳秒的时间尺度上，由此诱导的电荷分离具有长达数百微秒的长寿命。另一方面，空穴俘获需要从亚皮秒到数百皮秒的时间，并且诱导的电荷分离具有几纳秒的寿命。随着CdS壳层厚度的增加，空穴俘获消失，而电子俘获仍然可以检测到。这些发现对于理解纳米片层和其他胶体纳米结构的光物理过程具有重要意义。
