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Thin-Film Silicon Photovoltaics: Characterization of Thin-Film Deposition and Analysis of Enhanced Light Trapping from Scattering Nanoparticle Arrays


Langeland, Krista S. (2012) Thin-Film Silicon Photovoltaics: Characterization of Thin-Film Deposition and Analysis of Enhanced Light Trapping from Scattering Nanoparticle Arrays. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ZS04-AH18.


Thin-film solar cells have the potential to significantly decrease the cost of a finished device by cutting materials cost, and the characteristics of carrier transport through a thin film can concurrently increase the device performance over that of a wafer-based cell while tolerating a higher defect density in the absorbing material. However, while silicon is an attractive material for use in solar cells due to its nearly ideal band gap for single-junction cells and its relative abundance, its inefficient absorption of infrared light necessitates the development of light-trapping techniques to avoid losses in current generation. This thesis research has focused on two important goals: the development of a scalable thin-film silicon deposition method that produces high-quality material at minimal cost, and the evaluation of light-trapping mechanisms that will increase photon absorption in these films. Hot-wire chemical vapor deposition is used to fabricate silicon thin films with high crystalline fractions even on inexpensive substrates, and films grown with appropriate growth conditions exhibit initial open-circuit voltages above 450 mV, and while challenges in passivation still exist, this research illustrates the potential of this highly scalable and inexpensive deposition technique. Silver and silicon subwavelength structures were then both fabricated and simulated on ultra-thin silicon films on SiO2 to evaluate their potential for increasing light absorption through plasmonic and physical scattering mechanisms, and spectral response measurements demonstrate over a ten-fold increase in carrier generation with a metal nanoparticle surface array. Periodic dielectric structures exhibit Bloch modes in both measurement and simulation, with an increase in overall quantum efficiency of over 11% from both a flat silicon layer and one that is randomly textured. These results highlight the significant role of scattering particle distribution in determining the light trapping characteristics in these devices. Design guidelines have been explored for exploiting resonant modes in these structures, and this thesis demonstrates the potential for both metal and dielectric surface arrays to dramatically increase light absorption in silicon thin films.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:thin-film silicon, nanoparticles, light trapping, HWCVD, plasmonics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Atwater, Harry Albert
Thesis Committee:
  • Atwater, Harry Albert (chair)
  • Greer, Julia R.
  • Haile, Sossina M.
  • Minnich, Austin J.
Defense Date:9 February 2012
Record Number:CaltechTHESIS:03072012-191033678
Persistent URL:
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Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6847
Deposited By: Krista Langeland
Deposited On:01 May 2012 22:27
Last Modified:08 Nov 2023 00:12

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