A comparison of different methods to determine the electron diffusion length in dye-sensitized solar cells

H X Wang, L A Peter

Research output: Contribution to journalArticle

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Abstract

A new steady-state method for determination of the electron diffusion length in dye-sensitized solar cells (DSCs) is described and illustrated with data obtained using cells containing three different types of electrolyte. The method is based on using near-IR absorbance methods to establish pairs of illumination intensity for which the total number of trapped electrons is the same at open circuit (where all electrons are lost by interfacial electron transfer) as at short circuit (where the majority of electrons are collected at the contact). Electron diffusion length values obtained by this method are compared with values derived by intensity-modulated methods and by impedance measurements under illumination. The results indicate that the values of electron diffusion length derived from the steady-state measurements are consistently lower than the values obtained by the non-steady-state methods. For all three electrolytes used in the study, the electron diffusion length was sufficiently high to guarantee electron collection efficiencies greater than 90%. Measurement of the trap distributions by near-IR absorption confirmed earlier observations of much higher electron trap densities for electrolytes containing Li+ ions. It is suggested that the electron trap distributions may not be intrinsic properties of the TiO2 nanoparticles but may be associated with electron-ion interactions.
LanguageEnglish
Pages18125-18133
Number of pages9
JournalJournal of Physical Chemistry C
Volume113
Issue number42
DOIs
StatusPublished - 2009

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electron diffusion
diffusion length
solar cells
dyes
Electrons
electrons
traps
electrolytes
Electrolytes
Electron traps
illumination
short circuits
impedance measurement
Lighting
Dye-sensitized solar cells
Ions
electron transfer
ions
Short circuit currents
nanoparticles

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A comparison of different methods to determine the electron diffusion length in dye-sensitized solar cells. / Wang, H X; Peter, L A.

In: Journal of Physical Chemistry C, Vol. 113, No. 42, 2009, p. 18125-18133.

Research output: Contribution to journalArticle

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abstract = "A new steady-state method for determination of the electron diffusion length in dye-sensitized solar cells (DSCs) is described and illustrated with data obtained using cells containing three different types of electrolyte. The method is based on using near-IR absorbance methods to establish pairs of illumination intensity for which the total number of trapped electrons is the same at open circuit (where all electrons are lost by interfacial electron transfer) as at short circuit (where the majority of electrons are collected at the contact). Electron diffusion length values obtained by this method are compared with values derived by intensity-modulated methods and by impedance measurements under illumination. The results indicate that the values of electron diffusion length derived from the steady-state measurements are consistently lower than the values obtained by the non-steady-state methods. For all three electrolytes used in the study, the electron diffusion length was sufficiently high to guarantee electron collection efficiencies greater than 90{\%}. Measurement of the trap distributions by near-IR absorption confirmed earlier observations of much higher electron trap densities for electrolytes containing Li+ ions. It is suggested that the electron trap distributions may not be intrinsic properties of the TiO2 nanoparticles but may be associated with electron-ion interactions.",
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