Ghent University Academic Bibliography

Advanced

Characterization and simulation of three-dimensional solid-state solar cells

Catelijne Grasso (2006)
abstract
Introduction : The newest PV technology that uses less material and cheaper materials and deposition methods (in order to lower the cost even more) resulted in extremely thin absorber solar cells, or ETA-cells. Such ETA-layers need to be applied to a nano-structured substrate. Dye-sensitized solar cells (DSSC’s) already fully use this potential but encounter a lot of long-term stability problems. In the cells studied in this thesis, both the organic absorber dye and the liquid electrolyte of the DSSC are replaced by a solid-state semiconductor and are called 3D-cells. The nanostructured substrate is nanoporous titanium dioxide (TiO2). Objective : Charge carrier generation and their transport to the contacts is separated in 3D-cells. This seems to be an advantage with respect to the one-dimensional standard and thin film technology, where charge generation and transport take place in the same materials. Our and other’s nanostructured solid-state cells however, do not seem to benefit from this three-dimensional feature like DSSC’s do. The question is why? Interface recombination : Different kind of nano- and microstructured 3D-cells are characterized and analyzed. In particular a dynamic model is presented which enables us to quantify the influence of recombination in these cells. Interface recombination turns out to be a crucial element in the determination of the final performance of a 3D-cell. Diffusion models : Detailed effective medium models are set-up which describe both steady-state and dynamic response of the cells. In one of the models, the cell is treated as an infinite network of flat band unit cells (i.e. there is no electric field on a microscopic level). In the other, an analytic diffusion model is set up with boundary conditions specific for the treated cell. Both models assume diffusion as the main driving force for electron transport; charge separation occurs due to the difference in electron negativity of the materials. Results : The diffusion coefficients that are found are in the same range as those found for DSSC’s. The main difference is in the lifetime of the electrons which is 104 times smaller for 3D-cells than for DSSC’s. Both analytic approximations of and full simulations with the analytic diffusion model revealed that the diffusion length is much smaller than the cell thickness, and also than the absorption depth of the light. In that case, the characteristic time constant associated with the break frequency of the optoelectronic photocurrent transfer function is equal to half the electron life time, the characteristic time constant associated with the break frequency of the optoelectronic photovoltage transfer function is equal to the electron life time. The quantum response is equal to the product of the electron diffusion length and the absorption coefficient, which in our case indeed yields a quantum response that is much smaller than one. At last, the analytic diffusion model turned out to represent the nanostructured solar cell in the same way as the proposed infinite network of flat-band unit cells.
Please use this url to cite or link to this publication:
author
promoter
organization
alternative title
Karakterisering en simulatie van driedimensionale vastestof-zonnecellen
year
type
dissertation
publication status
published
subject
pages
IV, 160 pages
publisher
Ghent University. Faculty of Engineering
place of publication
Ghent, Belgium
defense location
Gent : Faculteit Ingenieurswetenschappen (Jozef Plateauzaal)
defense date
2006-02-24 16:00
ISBN
9789085780502
language
English
UGent publication?
yes
classification
D1
additional info
number of pages is based on printed version, which differs from digital version attached to this record
copyright statement
I have retained and own the full copyright for this publication
id
1888310
handle
http://hdl.handle.net/1854/LU-1888310
date created
2011-08-12 13:06:30
date last changed
2017-01-16 10:38:28
@phdthesis{1888310,
  abstract     = {Introduction : The newest PV technology that uses less material and cheaper materials and deposition methods (in order to lower the cost even more) resulted in extremely thin absorber solar cells, or ETA-cells. Such ETA-layers need to be applied to a nano-structured substrate. Dye-sensitized solar cells (DSSC{\textquoteright}s) already fully use this potential but encounter a lot of long-term stability problems. In the cells studied in this thesis, both the organic absorber dye and the liquid electrolyte of the DSSC are replaced by a solid-state semiconductor and are called 3D-cells. The nanostructured substrate is nanoporous titanium dioxide (TiO2).
Objective : Charge carrier generation and their transport to the contacts is separated in 3D-cells. This seems to be an advantage with respect to the one-dimensional standard and thin film technology, where charge generation and transport take place in the same materials. Our and other{\textquoteright}s nanostructured solid-state cells however, do not seem to benefit from this three-dimensional feature like DSSC{\textquoteright}s do. The question is why?
Interface recombination : Different kind of nano- and microstructured 3D-cells are characterized and analyzed. In particular a dynamic model is presented which enables us to quantify the influence of recombination in these cells. Interface recombination turns out to be a crucial element in the determination of the final performance of a 3D-cell.
Diffusion models : Detailed effective medium models are set-up which describe both steady-state and dynamic response of the cells. In one of the models, the cell is treated as an infinite network of flat band unit cells (i.e.
there is no electric field on a microscopic level). In the other, an analytic diffusion model is set up with boundary conditions specific for the treated cell. Both models assume diffusion as the main driving force for electron transport; charge separation occurs due to the difference in electron negativity of the materials.
Results : The diffusion coefficients that are found are in the same range as those found for DSSC{\textquoteright}s. The main difference is in the lifetime of the electrons which is 104 times smaller for 3D-cells than for DSSC{\textquoteright}s. Both analytic approximations of and full simulations with the analytic diffusion model revealed that the diffusion length is much smaller than the cell thickness, and also than the absorption depth of the light. In that case, the characteristic time constant associated with the break frequency of the optoelectronic photocurrent transfer function is equal to half the electron life time, the characteristic time constant associated with the break frequency of the optoelectronic photovoltage transfer function is equal to the
electron life time. The quantum response is equal to the product of the electron diffusion length and the absorption coefficient, which in our case indeed yields a quantum response that is much smaller than one. At last, the analytic diffusion model turned out to represent the nanostructured solar cell in the same way as the proposed infinite network of flat-band unit cells.},
  author       = {Grasso, Catelijne},
  isbn         = {9789085780502},
  language     = {eng},
  pages        = {IV, 160},
  publisher    = {Ghent University. Faculty of Engineering},
  school       = {Ghent University},
  title        = {Characterization and simulation of three-dimensional solid-state solar cells},
  year         = {2006},
}

Chicago
Grasso, Catelijne. 2006. “Characterization and Simulation of Three-dimensional Solid-state Solar Cells”. Ghent, Belgium: Ghent University. Faculty of Engineering.
APA
Grasso, C. (2006). Characterization and simulation of three-dimensional solid-state solar cells. Ghent University. Faculty of Engineering, Ghent, Belgium.
Vancouver
1.
Grasso C. Characterization and simulation of three-dimensional solid-state solar cells. [Ghent, Belgium]: Ghent University. Faculty of Engineering; 2006.
MLA
Grasso, Catelijne. “Characterization and Simulation of Three-dimensional Solid-state Solar Cells.” 2006 : n. pag. Print.