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Project
Spin-selective charge carrier injection, transport and recombination using chiral interfaces.
Spin-polarized charge carrier injection and transport are the subject of extensive research in the field of spintronics. This technology aims to exploit not only the electron's charge but also its intrinsic spin andits associated magnetic moment. Organic molecules, characterised by their low spin-orbit coupling and small hyperfine interactions, seem very promising as spin-transporting materials (with spin-relaxation timesbetween 0.1 and 10 microseconds). Nevertheless, previous attemptsto obtain spin-polarized transport through organic materials led to a rather low spin-polarization at room temperature. These attempts were, however, were all using a configuration with an achiral organic transport layer between two inorganic magnetic electrodes as spin-polarisers.Among others, Talliani et al. were able to relate the lack of spin-polarization to the Curie temperature and the surface magnetisation of theseinorganic electrodes. It is therefore appropriate to look for other types of spin-polarization.
Chiral molecules can offer this alternative, either by causing a significant spin-polarization by themselves, or by strengthening the pre-polarisation obtained using magnetic electrodes. This effect is based on a selective interaction between chiral molecules and chiral charge carriers.
The first advantage of efficient spin-polarization at room temperature, in additionto progress in organic spintronics itself, is undoubtedly an increase in OLED efficiency. Recombination between any two spins leads to a 1:3 ratio between (fluorescent) singlet excitons and (non-fluorescent) triplet excitons. Recombination between anti-parallel spins, on the other hand, would boost this ratio to 1:1.
Our objective is therefore threefold:
(1) Prove spin-polarized charge injection, or the improvement thereof, using chiral molecules and determine the relevant parameters.
(2) Show that spin is conserved during the charge transfer from the chiral to an achiral layer.
(3) The construction and characterization of an OLED with spin-polarized injection of both electrons and holes.
Chiral molecules can offer this alternative, either by causing a significant spin-polarization by themselves, or by strengthening the pre-polarisation obtained using magnetic electrodes. This effect is based on a selective interaction between chiral molecules and chiral charge carriers.
The first advantage of efficient spin-polarization at room temperature, in additionto progress in organic spintronics itself, is undoubtedly an increase in OLED efficiency. Recombination between any two spins leads to a 1:3 ratio between (fluorescent) singlet excitons and (non-fluorescent) triplet excitons. Recombination between anti-parallel spins, on the other hand, would boost this ratio to 1:1.
Our objective is therefore threefold:
(1) Prove spin-polarized charge injection, or the improvement thereof, using chiral molecules and determine the relevant parameters.
(2) Show that spin is conserved during the charge transfer from the chiral to an achiral layer.
(3) The construction and characterization of an OLED with spin-polarized injection of both electrons and holes.
Date:1 Jan 2011 → 15 Jan 2017
Keywords:Chiral moleculaes, OLEDs, Spin valves, Spin-selection, Organic spintronics, Chirality, Organics semiconductors, Helicenes
Disciplines:Sustainable chemistry, Physical chemistry, Inorganic chemistry, Organic chemistry, Theoretical and computational chemistry, Other chemical sciences
Project type:PhD project