Aboma Merdasa
Researcher
Super-resolution Luminescence Micro-Spectroscopy : A nano-scale view of solar cell material photophysics
Author
Summary, in English
Currently there is a growing notion that these methods can be applied in physics and chemistry to study photo-induced phenomena in materials with resolution at the nanoscale. The aim of this thesis is to explore and develop these possibilities to study energy and charge transport in functional materials interesting for light harvesting and solar-energy conversion. We present a novel wide-field super-resolution microscopy method adapted from localization microscopy. In combination with fluorescence spectroscopy it allows for an interrogation of a material’s photophysical properties down to the nanometer scale. We call the method super-resolution luminescence micro-spectroscopy (SuperLuMS).
One of the examples that we present here is a study of energy migration and trapping in individual molecular J-aggregates. We show that so-called ‘outliers’ (seldomly occurring trapping states) completely determine the exciton transport and dominate the fluorescence response. We also show that hybrid organic-inorganic perovskites are ideal objects for luminescence microscopy. These “hot” solar cell and light-emitting materials possess rich structures at scales just beyond optical diffraction limit making them an ideal “playground” for employing SuperLuMS and demonstrating its abilities.
The dynamics of charge carrier recombination in these materials is controlled by trapping and, as we demonstrate here, possess a great spatial inhomogeniety. For the first time we showed that one single trap can control the fate of charge carries in micrometer sized perovskite crystals which has important consequences for optical design of solar cells and other optoelectronic devices. We were also able to observe details of light-induced degradation and crystal phase transition in individual hybrid organic-inorganic perovskite crystals.
We believe SuperLuMS is an approach which will continue to evolve and find more diverse applications in material science.
Department/s
- Chemical Physics
Publishing year
2017-01
Language
English
Full text
Document type
Dissertation
Publisher
Lund University, Faculty of Science, Department of Chemistry, Division of Chemical Physics
Topic
- Atom and Molecular Physics and Optics
- Materials Chemistry
Keywords
- super-resolution microscopy
- Single Molecule Spectroscopy
- J-aggregates
- perovskites
- photophysics
Status
Published
Supervisor
- Ivan Scheblykin
ISBN/ISSN/Other
- ISBN: 978-91-7422-497-9
- ISBN: 978-91-7422-496-2
Defence date
27 January 2017
Defence time
10:15
Defence place
Lecture hall B, Department of Chemistry, Naturvetarvägen 14, Lund
Opponent
- Maria Antonietta Loi (Prof. Dr.)