Item – Theses Canada

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OCLC number
1033009968
Link(s) to full text
LAC copy
LAC copy
Author
Halliop, Basia,1981-
Title
Interface Properties of the Amorphous SiliconCrystalline Silicon Heterojunction photovoltaic cell.
Degree
(Ph. D.)--University of Toronto, 2015.
Publisher
Toronto : University of Toronto, 2015.
Description
1 online resource
Notes
Includes bibliographical references.
Abstract
Amorphous-crystalline silicon (a-Si:H/c-Si) heterojunctions have the potential of being a very high efficiency silicon photovoltaic platform technology with accompanying cost and energy budget reductions. In this research a heterojunction cell structure based on a-Si:H deposited using a DC saddle field plasma enhanced vapour deposition (DCSF PECVD) technique is studied, and the a-Si:H/c-Si and indium tin oxide/a-Si:H interfaces are examined using several characterization methods.Photocarrier radiometry (PCR) is used for the first time to probe the a-Si:H/c-Si junction. PCR is demonstrated as a carrier lifetime measurement technique - specifically, confirming carrier lifetimes above 1 ms for 1-5 Ohm.cm phosphorous-doped c-Si wafers passivated on both sides with 30 nm of i-a-Si:H. PCR is also used to determine surface recombination velocity and mobility, and to probe recombination at the a-Si:H/c-Si interface, distinguishing interface recombination from recombination within the a-Si:H layer or at the a-Si:H surface.A complementary technique, lateral conductivity is applied over a temperature range of 140 K to 430 K to construct energy band diagrams of a-Si:H/c-Si junctions. Boron doped a-Si:H films on glass are shown to have activation energies of 0.3 to 0.35 eV, tuneable by adjusting the diborane to silane gas ratio during deposition. Heterojunction samples show evidence of a strong hole inversion layer and a valence band offset of approximately 0.4 eV; carrier concentration in the inversion layer is reduced in p-a-Si:H/i-a-Si:H/c-Si structures as intrinsic layer thickness increases, while carrier lifetime is increased.The indium tin oxide/amorphous silicon interface is also examined. Optimal ITO films were prepared with a sheet resistance of 17.3 Ohm/square and AM1.5 averaged transmittance of 92.1%., for a film thickness of approximately 85 nm, using temperatures below 200 degrees celcius. Two different heat treatments are found to cause crystallization of ITO and to change the properties of the underlying a-Si:H film.Finally, an open circuit voltage of 699 mV was achieved using DCSF PECVD in the tetrode configuration to fabricate a metal/ITO/p-a-Si:H/i-a-Si:H/n-c-Si/i-a-Si:H/n+-a-Si:H/metal photovoltaic cell on a texturized wafer. The 4 cm2 cell had an efficiency of 16.5%, a short circuit current of 36.4 mA/cm2 and a fill factor of 64.7%.
Other link(s)
tspace.library.utoronto.ca
hdl.handle.net
Subject
amorphous silicon.
crystalline silicon.
heterojunction.
passivation.
photocarrier radiometry.
photovoltaics.