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Nanostructured Inverted Organic Photovoltaic Cells
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- Author / Creator
- Thomas, Michael
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Organic photovoltaic cells (OPVs)are promising devices for inexpensive power
generation from sunlight. Organic semiconductors, the basic materials
for OPVs, can be fabricated using a broad range of fabrication technologies
from vapor deposition to solution processing. Upon light absorption, a
strongly bound exciton is generated which can diffuse to a donor-acceptor
heterojunction. At this interface it can be dissociated into free charge carriers
which can be collected by the device electrodes. A major challenge for OPVs
are short exciton diffusion lengths of up to 20 nm. Morphology engineering
is required in order to harvest the exciton before it recombines and improve
OPV performance.
This work focuses on the study of nanostructured morphologies for use in
inverted architecture OPVs. Glancing angle deposition (GLAD)is employed
to fabricate nanocolumnar acceptor films. Through combining these nanostructured
C60 films with a conjugated polymer donor P3CBT and a small
molecule 3-Q, inverted OPVs are fabricated with the goal to analyze effect
of morphology engineering on device performance. A major challenge was
that C60 were found to be soluble in most commonly used organic solvents
such as dichlorobenzene or chloroform. Although this challenge has limited
the donor choice and therefore has limited device performance, a significant
effect of morphology engineering could be observed. All GLAD structured
C60 OPVs outperformed state of the art architectures such as planar films and
bulk heterojunctions fabricated with the same materials. For P3CBT in particular
the GLAD structured devices exhibited a twofold increase in power
conversion efficiency compared with bulk heterojunctions and a fourfold increase
compared with planar devices.
In a further study, the acceptor materials PTCDA and C60 were co-evaporated
into a single film. PTCDA is stable against non-polar organic solvents while
C60 provides a high electron mobility. Nanocolumnar acceptor blended PTCDA:C60
films were proven to remain stable when treated with dichlorobenzene. Furthermore,
optical and electronic properties of these acceptor blends were investigated. -
- Subjects / Keywords
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- Graduation date
- Spring 2013
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.