Ultrafast action spectroscopy of organic semiconductors and optoelectronic devices
File(s)
Author(s)
Maimaris, Marios
Type
Thesis
Abstract
Research on organic semiconductors for optoelectronic application has grown exponentially in recent decades, driven by the urgent need to replace silicon and fossil fuels. Towards this quest spectroscopists’ task is to spectro-temporally investigate dynamics of organic semiconductors to provide insights for efficient organic optoelectronic devices. With the development of ultrafast pulses down to ~10 fs, unprecedented processes like exciton binding can now be explored. Up to now most ultrafast dynamics investigations are dedicated on films or monomer molecules by using spectroscopy techniques based on coherent responses. Although such investigations are elucidating many phenomena and giving significant insights on organic semiconductors dynamics, they are still distant from the actual operating devices questioning the direct link between experimental dynamics and device performance. Herein, for the first time, ~10 fs ultrafast action spectroscopies based on photocurrent and photoluminescence response are applied on organic solar cell devices under operando conditions tracking dynamics which are directly linked with device performance. Initially, a model polymer based single component organic solar cell is under investigation which demonstrates ~10 fs ultrafast binding of near-band-edge excitons. Using a model system is rather beneficial as it can ease the process of formulating the experimental framework and methodology for ultrafast action spectroscopies applied on optoelectronic devices. Then, the research shifts to more complex systems, that is, non-fullerene single component organic solar cell whose blends with donor-molecules are responsible for the current record efficiencies. Results shows a favourable transition of exitonic state towards delocalised unbound charge transfer state. Following this observation, ultrafast 2-dimensional electronic spectroscopy is employed to investigate the nature and energetics of such charge transfer states by exploiting the induced quantum coherences. All in all, this thesis demonstrates ultrafast action spectroscopy applied on optoelectronic devices under operando conditions showcasing its value as a powerful tool in spectroscopists’ arsenal.
Version
Open Access
Date Issued
2024-08
Date Awarded
2024-10
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)