Control and characterisation of metal oxide/polymer morphologies for hybrid photovoltaic devices
File(s)
Author(s)
Downing, Jonathan Mark
Type
Thesis
Abstract
The ready formation of nanostructures, combined with excellent optoelectronic
properties has shown zinc oxide (ZnO) to be a promising material for use in
photovoltaic devices. Hybrid photovoltaic (h-PV) devices composed of metal
oxide-organic pairings are currently limited by ineffective charge transfer between
the materials and by poor transport of free charge out of the active layer. Control
of interfacial properties, and the structure and morphology of each component
is key to device optimisation. In this thesis, ZnO nanorods are paired with the
photoactive polymer, poly 3-hexlythiophene (P3HT) with two areas studied: i)
nanorod alignment to aid polymer infiltration, and ii) elucidating optimum polymer
processing conditions to prepare efficient devices.
Aligned nanorods are synthesised from ZnO coated substrates by a hydrothermal
method. To understand the influence of ionic additives on morphological control,
the addition of potassium chloride (KCl) to growth solutions is investigated. Films
have been studied by SEM and XRD, with the correlation of these results (nanorod
length, width, density vs (002) diffraction peak area) used to examine alignment,
which increases at higher concentrations. This ordering is explained via a geometrical
selection argument.
Effective polymer infiltration into nanorod arrays is found to be possible by
spin coating and annealing above the polymer melting point. Extended annealing
(> 60 seconds) is seen to reduce device performance. Small angle X-ray scattering
and X-ray diffraction as a function of temperature was conducted to investigate
polymer orientation and the kinetics of crystallisation within nanostructured films.
These results are combined with device measurements to aid in understanding the
relationship between morphological characteristics of the constituent materials and
h-PV performance.
properties has shown zinc oxide (ZnO) to be a promising material for use in
photovoltaic devices. Hybrid photovoltaic (h-PV) devices composed of metal
oxide-organic pairings are currently limited by ineffective charge transfer between
the materials and by poor transport of free charge out of the active layer. Control
of interfacial properties, and the structure and morphology of each component
is key to device optimisation. In this thesis, ZnO nanorods are paired with the
photoactive polymer, poly 3-hexlythiophene (P3HT) with two areas studied: i)
nanorod alignment to aid polymer infiltration, and ii) elucidating optimum polymer
processing conditions to prepare efficient devices.
Aligned nanorods are synthesised from ZnO coated substrates by a hydrothermal
method. To understand the influence of ionic additives on morphological control,
the addition of potassium chloride (KCl) to growth solutions is investigated. Films
have been studied by SEM and XRD, with the correlation of these results (nanorod
length, width, density vs (002) diffraction peak area) used to examine alignment,
which increases at higher concentrations. This ordering is explained via a geometrical
selection argument.
Effective polymer infiltration into nanorod arrays is found to be possible by
spin coating and annealing above the polymer melting point. Extended annealing
(> 60 seconds) is seen to reduce device performance. Small angle X-ray scattering
and X-ray diffraction as a function of temperature was conducted to investigate
polymer orientation and the kinetics of crystallisation within nanostructured films.
These results are combined with device measurements to aid in understanding the
relationship between morphological characteristics of the constituent materials and
h-PV performance.
Version
Open Access
Date Issued
2013-03
Date Awarded
2013-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Ryan, Mary
McLachlan, Martyn
Sponsor
Engineering and Physical Sciences Research Council
Amrourers & Brassiers
Imperial College London
Creator
Downing, Jonathan Mark
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)