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Light Management in Silicon Nanostructures for Photovoltaics

Wang, Baomin (2016) Light Management in Silicon Nanostructures for Photovoltaics. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The main challenge with the use of silicon for photovoltaics is that silicon is not a strong absorber of sunlight in the near-infrared region. Conventional silicon photovoltaics are thus typically of thicknesses 200 to 300 _m to ensure the absorption of most sunlight. However, single crystalline silicon solar cells require expensive manufacturing methods. So current solar cell technology is not as competitive as that of traditional energy sources. To promote and increase the silicon solar cell capacity, costs need to drop below $1/W. Increasing absorption of light in the absorber layers is critical issue for achieving high efficiency silicon solar cells. Various light trapping methods have been developed, experimentally and computationally. Light trapping with sub-wavelength nanostructures involves coupling light into localized resonant modes and guided resonance modes in active region to increase absorption. Nanophotonic light trapping strategies have used structuring of the silicon itself or patterning of dielectric materials on front and back of silicon.

In order to continue developing cheap and high efficiency silicon solar cells, we studied several anti-reflection and light trapping structures with lower cost and higher absorption. First of all, tapered nanocone structure was proposed and studied and then fabricated via Bosch process. Secondly, high refractive index nanosphere scheme was investigated as a light trapping strategy which does not create new surface or interface and is easy to fabricate. Then inverse woodpile and woodpile photonic crystal structures were studied and proven to have superior light trapping ability due to the ability to engineer the photonic density of states.

Finally, ultrathin silicon was fabricated via wet etching method, and then high refractive index nanosphere layers were coated and the power conversion efficiency was increased by 26.5%. Furthermore, metal nanomesh was used as front contact to substitute traditional indium tin oxide, and the power conversion efficiency was increased by 53% due to high haze factor and lower sheet resistance of the metal nanomesh. More importantly, with the metal nanomesh as front contact, the ultrathin silicon solar cells showed superior flexibility.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Wang, Baominwbmpitt@gmail.comBAW57
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLeu, Paul
Committee MemberChen,
Committee MemberBidanda,
Committee MemberChun, Young
Thesis AdvisorLeu, Paul
Date: 15 June 2016
Date Type: Publication
Defense Date: 29 January 2016
Approval Date: 15 June 2016
Submission Date: 23 March 2016
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 120
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Industrial Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: silicon, nanostructures, photovoltaics, light management
Date Deposited: 15 Jun 2016 18:54
Last Modified: 15 Jun 2017 05:15


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