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Name (Title):
Liyuan Han
Affiliation:
WPI Center for Materials Nanoarchitectnics, National Institute for Materials
Science
Address:
1-2-1 Sengen Tsukuba, Ibaraki, 305-0047, Japan
Email: han.liyuan@nims.go.jp
Home Page: http://www.nims.go.jp/mana/members/principal_investigator/l_han/index.html
Presentation Title:
Highly Efficient Dye-sensitized Solar Cells
Abstract:
Dye-sensitized solar cells (DSCs) have been widely investigated as a next-generation solar cell
because of low manufacturing cost. A dye-sensitized solar cell, generally, comprises a
nanocrystalline titanium dioxide electrode modified with a dye fabricated on a transparent
conducting oxide, a platinum counter electrode, and an electrolyte solution with a dissolved
iodide ion/tri-iodide ion redox couple between the electrodes. In this presentation, strategy for
improving efficiency of DSCs was reported. Modeling of equivalent circuit of DSCs, the method
for improvement of shirt circuit density (Jsc), open circuit voltage and fill factor were
investigated. To understand the mechanism of DSC, an internal resistance was studied by the
electrochemical impedance spectroscopy and four internal resistance elements were observed.
These were assigned to the charge transfer processes at the counter electrode (R1), the charge
transportation at the TiO2/dye/electrolyte interface (R2), the diffusion of iodide and triiodide in the
electrolyte (R3), and the sheet resistance of transparent conducting oxide (Rh). An equivalent
circuit model 1) of DSCs is proposed based on these results (Fig. 1).The decrease of the seriesinternal
resistance was studied based on the equivalent circuit of DSCs in order to improve of fill
factor. It is found that the series-internal resistance decreases with increase of the roughness
factor of the counter electrodes, the decrease of the thickness of the electrolyte layer and the sheet
resistance of the transparent conducting oxide. For the purpose of improving Jsc, dependence of
incident photon to current conversion efficiency
(IPCE) spectra on haze of TiO2 film was investigated.
IPCE is widely increased with increase of the haze of
TiO2 film, especially in infrared region. A cell with the
series-internal resistance of 1.8 Ωcm 2 and high haze
factor was fabricated. Current-voltage characteristics
were measured by Research Center for Photovoltaic,
National Institute of Advanced Industrial Science and
Technology (AIST, Japan) using a metal mask and
with an aperture area of 0.219 cm 2 under standard AM
1.5 sunlight (100.0 mW/cm 2 ). An overall conversion
efficiency of 11.1% was achieved which is the highest
confirmed efficiency. Finally I will talk how to further
improve the conversion efficiency.
Reference:
1) L. Han, N. Koide, Y. Chiba and T. Mitate, Appl. Phys. Lett., 84, 2433 (2004).
Oral Presentation 39
Fig. 1 Equivalent circuit of DSCs. R1, R3 and
Rh are series resistance elements, Rsh is shunt
resistance, C1 and C3 are capacitance element.
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