Ultrafast nanoscopy and multi-dimensional spectroscopy of processible photovoltaic materials
File(s)
Author(s)
Ning, Haoqing
Type
Thesis
Abstract
Advancements in electronic devices, quantum computing, and optical computing depend on novel nanomaterials, including low-nanometer semiconductors and two-dimensional materials. This thesis addresses the need for characterization techniques with high spatial-temporal resolution and dark state observation in new materials, using advanced ultrafast spectroscopy methods: on-chip ultrafast electron detection and multidimensional correlation spectroscopy with coherent excitation.
The first part introduces an on-chip ultrafast nanoscale detection method to achieve femtosecond temporal and nanometer spatial resolution. A photosensitive asymmetric nanogap (PAN) was created using a novel adhesion lithography technique. PAN demonstrates an ultrafast nonlinear current response spanning the DUV to mid-infrared range. This response depends on peak field strength rather than photon energy, indicating Fowler-Nordheim field emission due to strong-field ionization. PAN has applications in crystal-free optical field sampling and probing ultrafast electronic dynamics of materials such as perovskite quantum dots on a nanoscale.
The second part uses two-dimensional electronic spectroscopy to investigate electron dynamics in singlet fission materials, focusing on the dark triplet pair state. By analyzing oscillatory population dynamics (beating maps), differences in fission rates between pentacene dimers highlight vibronic coupling effects and propose a refined energy diagram post-state hybridization.
These findings extend ultrafast spectroscopy, enhance spatial resolution and spectral depth, and provide insights critical for future nanomaterial and optoelectronic applications.
The first part introduces an on-chip ultrafast nanoscale detection method to achieve femtosecond temporal and nanometer spatial resolution. A photosensitive asymmetric nanogap (PAN) was created using a novel adhesion lithography technique. PAN demonstrates an ultrafast nonlinear current response spanning the DUV to mid-infrared range. This response depends on peak field strength rather than photon energy, indicating Fowler-Nordheim field emission due to strong-field ionization. PAN has applications in crystal-free optical field sampling and probing ultrafast electronic dynamics of materials such as perovskite quantum dots on a nanoscale.
The second part uses two-dimensional electronic spectroscopy to investigate electron dynamics in singlet fission materials, focusing on the dark triplet pair state. By analyzing oscillatory population dynamics (beating maps), differences in fission rates between pentacene dimers highlight vibronic coupling effects and propose a refined energy diagram post-state hybridization.
These findings extend ultrafast spectroscopy, enhance spatial resolution and spectral depth, and provide insights critical for future nanomaterial and optoelectronic applications.
Version
Open Access
Date Issued
2024-06
Date Awarded
2024-11
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Bakulin, Artem
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)