Nanostructured Inverted Organic Photovoltaic Cells

• Author / Creator

  Thomas, Michael

• 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

  • C60 Fullerene
  • Nanostructures
  • Glancing angle deposition
  • Organic photovoltaics
  • Bulk heterojunction

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3W333

• 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.