A Caltech Library Service

Mesoscale Optoelectronic Design of Wire-Based Photovoltaic and Photoelectrochemical Devices


Fountaine, Katherine Theresa (2015) Mesoscale Optoelectronic Design of Wire-Based Photovoltaic and Photoelectrochemical Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9P26W1K.


The overarching theme of this thesis is mesoscale optical and optoelectronic design of photovoltaic and photoelectrochemical devices. In a photovoltaic device, light absorption and charge carrier transport are coupled together on the mesoscale, and in a photoelectrochemical device, light absorption, charge carrier transport, catalysis, and solution species transport are all coupled together on the mesoscale. The work discussed herein demonstrates that simulation-based mesoscale optical and optoelectronic modeling can lead to detailed understanding of the operation and performance of these complex mesostructured devices, serve as a powerful tool for device optimization, and efficiently guide device design and experimental fabrication efforts. In-depth studies of two mesoscale wire-based device designs illustrate these principles—(i) an optoelectronic study of a tandem Si|WO3 microwire photoelectrochemical device, and (ii) an optical study of III-V nanowire arrays.

The study of the monolithic, tandem, Si|WO3 microwire photoelectrochemical device begins with development and validation of an optoelectronic model with experiment. This study capitalizes on synergy between experiment and simulation to demonstrate the model’s predictive power for extractable device voltage and light-limited current density. The developed model is then used to understand the limiting factors of the device and optimize its optoelectronic performance. The results of this work reveal that high fidelity modeling can facilitate unequivocal identification of limiting phenomena, such as parasitic absorption via excitation of a surface plasmon-polariton mode, and quick design optimization, achieving over a 300% enhancement in optoelectronic performance over a nominal design for this device architecture, which would be time-consuming and challenging to do via experiment.

The work on III-V nanowire arrays also starts as a collaboration of experiment and simulation aimed at gaining understanding of unprecedented, experimentally observed absorption enhancements in sparse arrays of vertically-oriented GaAs nanowires. To explain this resonant absorption in periodic arrays of high index semiconductor nanowires, a unified framework that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes is developed in the context of silicon, using both analytic theory and electromagnetic simulations. This detailed theoretical understanding is then applied to a simulation-based optimization of light absorption in sparse arrays of GaAs nanowires. Near-unity absorption in sparse, 5% fill fraction arrays is demonstrated via tapering of nanowires and multiple wire radii in a single array. Finally, experimental efforts are presented towards fabrication of the optimized array geometries. A hybrid self-catalyzed and selective area MOCVD growth method is used to establish morphology control of GaP nanowire arrays. Similarly, morphology and pattern control of nanowires is demonstrated with ICP-RIE of InP. Optical characterization of the InP nanowire arrays gives proof of principle that tapering and multiple wire radii can lead to near-unity absorption in sparse arrays of InP nanowires.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:photovoltaic; photoelectrochemistry; semiconductor nanowire; nanowire array; MOCVD; OMVPE; MOVPE; RIE; ICP-RIE; optical; optoelectronic; microwire; mesoscale; nanofabrication
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Atwater, Harry Albert
Group:Kavli Nanoscience Institute, JCAP
Thesis Committee:
  • Atwater, Harry Albert (chair)
  • Brady, John F.
  • Lewerenz, Hans Joachim
  • Flagan, Richard C.
Defense Date:19 May 2015
Non-Caltech Author Email:katefountaine (AT)
Funding AgencyGrant Number
National Science FoundationGraduate Research Fellowship
DOE Office of Basic Science DE-SC0004993
Record Number:CaltechTHESIS:05292015-151831184
Persistent URL:
Related URLs:
URLURL TypeDescription
http://daedalus.caltech.eduOrganizationAtwater group webpage
http://solarfuelshub.orgOrganizationJoint Center for Artificial Photosynthesis webpage
Fountaine, Katherine Theresa0000-0002-0414-8227
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8928
Deposited By: Katherine Fountaine
Deposited On:05 Oct 2016 22:37
Last Modified:08 Nov 2023 18:46

Thesis Files

PDF (Thesis) - Final Version
See Usage Policy.


Repository Staff Only: item control page