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Photonic and Device Design Principles for Ultrahigh-Efficiency (>50%), Spectrum-Splitting Photovoltaics


Eisler, Carissa Nicole (2016) Photonic and Device Design Principles for Ultrahigh-Efficiency (>50%), Spectrum-Splitting Photovoltaics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9PN93HB.


The sun has the potential to power the Earth's total energy needs, but electricity from solar power still constitutes an extremely small fraction of our power generation because of its high cost relative to traditional energy sources. Therefore, the cost of solar must be reduced to realize a more sustainable future. This can be achieved by significantly increasing the efficiency of modules that convert solar radiation to electricity. In this thesis, we consider several strategies to improve the device and photonic design of solar modules to achieve record, ultrahigh (> 50%) solar module efficiencies. First, we investigate the potential of a new passivation treatment, trioctylphosphine sulfide, to increase the performance of small GaAs solar cells for cheaper and more durable modules. We show that small cells (mm2), which currently have a significant efficiency decrease (~ 5%) compared to larger cells (cm2) because small cells have a higher fraction of recombination-active surface from the sidewalls, can achieve significantly higher efficiencies with effective passivation of the sidewalls. We experimentally validate the passivation qualities of treatment by trioctylphosphine sulfide (TOP:S) through four independent studies and show that this facile treatment can enable efficient small devices. Then, we discuss our efforts toward the design and prototyping of a spectrum-splitting module that employs optical elements to divide the incident spectrum into different color bands, which allows for higher efficiencies than traditional methods. We present a design, the polyhedral specular reflector, that has the potential for > 50% module efficiencies even with realistic losses from combined optics, cell, and electrical models. Prototyping efforts of one of these designs using glass concentrators yields an optical module whose combined spectrum-splitting and concentration should correspond to a record module efficiency of 42%. Finally, we consider how the manipulation of radiatively emitted photons from subcells in multijunction architectures can be used to achieve even higher efficiencies than previously thought, inspiring both optimization of incident and radiatively emitted photons for future high efficiency designs. In this thesis work, we explore novel device and photonic designs that represent a significant departure from current solar cell manufacturing techniques and ultimately show the potential for much higher solar cell efficiencies.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:photovoltaics, spectrum-splitting, passivation, solar cell, multijunction
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Applied Physics
Awards:Everhart Distinguished Graduate Student Lecturer Award, 2015. Gray Hills Lecture Series: Selected Lecturer, 2014. National Defense Science and Engineering Graduate (NDSEG) Fellowship Recipient
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Atwater, Harry Albert
Thesis Committee:
  • Flagan, Richard C. (chair)
  • Kornfield, Julia A.
  • Faraon, Andrei
  • Atwater, Harry Albert
Defense Date:3 November 2015
Non-Caltech Author Email:carissaeisler (AT)
Funding AgencyGrant Number
Department of EnergyDE-FG02-07ER46405
‘Light–Material Interactions in Energy Conversion’ Energy Frontier Research CenterDE-SC0001293
DARPA Portable PhotovoltaicsUNSPECIFIED
Dow Chemical Company UNSPECIFIED
Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of EnergyDE-AR0000333
Record Number:CaltechTHESIS:11242015-234332347
Persistent URL:
Eisler, Carissa Nicole0000-0002-5755-5280
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9292
Deposited By: Carissa Eisler
Deposited On:04 Dec 2015 23:17
Last Modified:08 Nov 2023 00:12

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