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dc.contributor.advisorSamuel, Ifor D. W.
dc.contributor.authorShaw, Paul E.
dc.coverage.spatial226en_US
dc.date.accessioned2009-12-10T17:09:02Z
dc.date.available2009-12-10T17:09:02Z
dc.date.issued2009-11-30
dc.identifier.urihttps://hdl.handle.net/10023/831
dc.description.abstractThe exciton diffusion length, which is the distance an exciton can diffuse in its lifetime, is an important parameter that has a critical impact on the operation of many organic optoelectronic devices, including organic solar cells, light emitting diodes and lasers. Knowledge of the exciton diffusion length can be a powerful aid for the design and optimisation of these devices. This thesis details the development of techniques based on time-resolved fluorescence for measuring the exciton diffusion in organic semiconductors. Two main methods were used to investigate exciton diffusion in the conjugated polymers P3HT, MEH-PPV and F8BT: the surface quenching technique and exciton-exciton annihilation. In particular, the surface quenching technique was adapted to avoid some of the potential pitfalls that have plagued earlier measurements. Using a titania quencher, measurements were performed using the surface quenching technique and fitted with an exciton diffusion model, allowing the calculation of the exciton diffusion length. Results from measurements of the exciton-exciton annihilation rate, which is a diffusion controlled process, where in good agreement with those from surface quenching, confirming the robustness of this twofold approach. A novel method for the control of the β-phase conformation in PFO films was used to produce films containing varying concentrations of β-phase. Exciton-exciton annihilation was used to investigate exciton diffusion in these films, revealing a gradual rise with increasing β-phase fraction due to improved interconnectivity. This work demonstrates how simple processing techniques can be used to control both film morphology and the exciton diffusion. The thickness dependence of the photoluminescence lifetime in conjugated polymers is a phenomenon that has so far received little attention and, thus, remained unexplained. This study demonstrates that it is not due to exciton quenching by external factors, but can be explained by a change in the morphology with decreasing film thickness.en_US
dc.language.isoenen_US
dc.publisherUniversity of St Andrews
dc.rightsCreative Commons Attribution-NoDerivs 3.0 Unported
dc.rights.urihttp://creativecommons.org/licenses/by-nd/3.0/
dc.subjectOrganic semiconductorsen_US
dc.subjectTime-resolved photophysicsen_US
dc.subjectExciton diffusionen_US
dc.subjectExciton-exciton annihilationen_US
dc.subject.lccQD382.C66S5
dc.subject.lcshConjugated polymersen
dc.subject.lcshExciton theoryen
dc.titleMeasurements of exciton diffusion in conjugated polymersen_US
dc.typeThesisen_US
dc.type.qualificationlevelDoctoralen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US


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Creative Commons Attribution-NoDerivs 3.0 Unported
Except where otherwise noted within the work, this item's licence for re-use is described as Creative Commons Attribution-NoDerivs 3.0 Unported