Black silicon and its applications in photovoltaics and biosensing

Xu, Zhida

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https://hdl.handle.net/2142/50433 Copy

Description

Title

Black silicon and its applications in photovoltaics and biosensing

Author(s)

Xu, Zhida

Issue Date

2014-09-16

Director of Research (if dissertation) or Advisor (if thesis)

Liu, Gang Logan

Doctoral Committee Chair(s)

Liu, Gang Logan

Committee Member(s)

• Eden, James G.
• Cunningham, Brian T.
• Goddard, Lynford L.

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• black silicon
• semiconductor
• plasmonics
• solar cell
• photovoltaics
• biosensing
• surface-enhanced Raman spectroscopy
• fluorescence

Abstract

Black silicon was produced with a lithography-free three-step plasma etching method. The nanocone forest on the silicon surface makes the silicon look black. Its applications in photovoltaics and biosensing were demonstrated by experiments. For photovoltaics, sub-100 nm nanocone forest was produced on commercial silicon solar cell with existing micro-structured antireflection layer. The reflection is further reduced by 70% and the conversion efficiency is increased by 14.7% relatively. Broadband and omnidirectional light-trapping black silicon was produced on ultrathin silicon micro solar cells. With optimized plasma etching conditions and a silicon nitride passivation layer, black silicon µ-cells, when embedded in a polymer waveguiding layer, display dramatic increases of as much as 65.7% in short circuit current, as compared to a bare silicon device. The conversion efficiency increases from 8% to 11.5% with a small drop in open circuit voltage and fill factor. For biosensing, the black silicon is deposited with coinage metal (Au, Ag) as surface plasmon-enhanced substrate for optical analysis including surface enhanced Raman spectroscopy (SERS) and fluorescence imaging. We call it “black silver” substrate. The unique physical property of the black silver substrate permits the enhancement in optical absorption from UV to NIR range by 12 times, the surface fluorescence enhancement of ~30 times and the Raman scattering enhancement factor as high as 6.38 × 10^7. In comparison with the printed results on ordinary glass slides and silver-coated glass slides, not only high printing density but uniform molecular distribution in every deposited spot is achieved. The high-uniformity and repeatability of molecular depositions on the “coffee stain”-free nanocone surface is confirmed by laser scanning fluorescence imaging and surface enhanced Raman imaging experiments. The physical mechanism for the uniform molecular deposition is attributed to the superhydrophobicity and localized pinned liquid–solid–air interface on the silver-coated silicon nanocone surface. The unique surface properties of the presented nanocone surface enabled high-density, high-uniformity probe spotting beneficial for genomic and proteomic microarrays and surface molecular imaging. In the end, to give an example of application of black silicon for proteomic assay, detection of phosphorylation of protein by SERS on black silver was implemented.

Graduation Semester

2014-08

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http://hdl.handle.net/2142/50433

Copyright and License Information

Copyright 2014 Zhida Xu

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