Spectroscopic Study of Triplet Exciton Dynamics at the Hybrid Organic-Inorganic Interface
type: CreativeWork
description: The control and utilisation of spin-triplet excitons in organic semiconductors is highly sought after for the next generation of Optoelectronic applications. Of particular interest is the utilisation of these photoexcited states in the singlet-fission photon-multiplier and triplet-triplet annihilation upconversion processes. Singlet fission is an exciton multiplication process in organic molecules, in which a photogenerated spin-singlet exciton is rapidly and efficiently converted into two spin-triplet excitons. Conversely, triplet-triplet annihilation is essentially the same reaction operating in reverse. These processes offer two spectral management mechanisms to break the Shockley–Queisser limit by overcoming the thermalisation and absorption losses inherent to all single-junction photovoltaics. Such spectral management technologies have been predicted to increase the maximum possible efficiency of Si-based cells from 32 % to greater than 40 %, breaking the Shockley–Queisser limit. Harnessing these processes would be facilitated if the energy of the triplet exciton could be efficiently interchanged with photons. However, utilising triplet excitons like this poses a significant challenge, as transitions between the ground state and triplet excited states typically have negligible mediation by photons. Transitions such as these are spin forbidden, and have a correspondingly weak oscillator strength. In this thesis, we investigate a promising method to overcome this impasse, using inorganic quantum dots (QDs) to efficiently convert between triplet excitons and photons. We develop a variety of novel hybrid organic-inorganic systems that perform singlet-fission photon-multiplication and triplet-triplet annihilation upconversion. We find that in order to achieve efficient triplet transfer at the hybrid organic-inorganic interface, it is critical to engineer the surface of the QD with a triplet transfer ligand. The triplet transfer ligand facilitates transfer by acting …
abstract: The control and utilisation of spin-triplet excitons in organic semiconductors is highly sought after for the next generation of Optoelectronic applications. Of particular interest is the utilisation of these photoexcited states in the singlet-fission photon-multiplier and triplet-triplet annihilation upconversion processes. Singlet fission is an exciton multiplication process in organic molecules, in which a photogenerated spin-singlet exciton is rapidly and efficiently converted into two spin-triplet excitons. Conversely, triplet-triplet annihilation is essentially the same reaction operating in reverse. These processes offer two spectral management mechanisms to break the Shockley–Queisser limit by overcoming the thermalisation and absorption losses inherent to all single-junction photovoltaics. Such spectral management technologies have been predicted to increase the maximum possible efficiency of Si-based cells from 32 % to greater than 40 %, breaking the Shockley–Queisser limit. Harnessing these processes would be facilitated if the energy of the triplet exciton could be efficiently interchanged with photons. However, utilising triplet excitons like this poses a significant challenge, as transitions between the ground state and triplet excited states typically have negligible mediation by photons. Transitions such as these are spin forbidden, and have a correspondingly weak oscillator strength. In this thesis, we investigate a promising method to overcome this impasse, using inorganic quantum dots (QDs) to efficiently convert between triplet excitons and photons. We develop a variety of novel hybrid organic-inorganic systems that perform singlet-fission photon-multiplication and triplet-triplet annihilation upconversion. We find that in order to achieve efficient triplet transfer at the hybrid organic-inorganic interface, it is critical to engineer the surface of the QD with a triplet transfer ligand. The triplet transfer ligand facilitates transfer by acting …
author: Allardice, Jesse
language: eng
keywords: Physics, Spectroscopy, Semiconductor
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/bc2bf766-fb7f-4999-8cf5-5a9edaf7321d/download
license: https://creativecommons.org/licenses/by/4.0/
date published: 2020-05-08
date modified: 2026-07-22T22:23:59Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.61811