Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596144
Title: Conjugated polymer phase separation and three-dimensional thin-film structure for photovoltaics
Author: Arias, A. C.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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Abstract:
The work presented in this thesis focuses on the subject of photovoltaic devices based on phase-separated blends of conjugated polymers. The advantage of the blend system used in this work is that both materials are optically and electrically active, and their morphologies and relative arrangement impact this activity so that the optimisation of phase separation can be directly applied to optoelectronic devices. A systematic study on device structure is presented, including the use of polymeric electrodes and the influence of the microstructure of thin films on device performance. Conventional fluorescence, fluorescence scanning near-field optical microscopy and atomic force microscopy have been combined to relate film morphology with photovoltaic and photoluminescence efficiencies as a function of surface treatment, concentration, and preparation conditions. The results presented in this dissertation are in agreement with the thermodynamics theory of phase separation developed for non-conjugated polymer composites. The phase-separated structures observed under different solvent evaporation conditions for the composite system study here are consistent with a spinodal-type decomposition mechanism. The composition of the phases was found to be of fundamental importance for device performance, assisting exciton dissociation in blends phase separated on scales larger than the exciton diffusion length. Vertical segregation of blend components was induced through specially developed solution-coating processes to produce a structure optimised for separated charge transport and collection. This self-organisation process, in conjunction with the phase compositions, has resulted in the demonstration of highest photovoltaic efficiencies reported for the polyfluorene materials. It is directly shown how the control of phase separation of a polymer binary blend system in the intermolecular, lateral, and vertical regime can be used to enhance and optimise device performance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.596144  DOI: Not available
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