Evaluation of the charge-collection efficiency of dye-sensitized nanocrystalline TiO{sub 2} solar cells

Journal Article · Thu Feb 04 04:00:00 EST 1999 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp9831177· OSTI ID:335255

Schlichthoerl, G; Park, N G; Frank, A J ^[1]

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1. National Renewable Energy Lab., Golden, CO (United States)

Intensity modulated photovoltage spectroscopy (IMVS) and intensity modulated photocurrent spectroscopy (IMPS) are used to evaluate the charge-collection efficiency of dye-sensitized nanocrystalline TiO{sub 2} solar cells. The charge-collection efficiency of the photoinjected electrons from dye sensitization is estimated from the respective time constants for charge recombination at open circuit {tau}{sub oc} and the combined processes of charge collection and charge recombination at short circuit {tau}{sub sc} obtained by IMVS and IMPS measurements. Three models are developed for relating the charge-collection efficiency to {tau}{sub oc}/{tau}{sub sc}. The first model determines the charge-collection efficiency from {tau}{sub oc}/{tau}{sub sc} without considering the underlying physical processes measured by IMVS and IMPS. The second model obtains {tau}{sub oc}/{tau}{sub sc} by simulating the frequency response of IMVS and IMPS from the time-dependent continuity equation for simplified conditions. The third model determines the time constants for IMVS and IMPS from electron-concentration profiles calculated for constant light intensity and more realistic conditions. To obtain a realistic steady-state electron concentration profile, a nonlinear dependence of the rate of recombination on the electron concentration in the TiO{sub 2} film is considered. Furthermore, the continuity equation is modified to account for charge trapping and detrapping. For the first time, expressions are derived for calculating the time constants from the steady-state electron concentration profile. The validity of this method is demonstrated for the second model from which the exact IMPS and IMVS responses are calculated. The three models are compared with each other. A simple expression is derived for calculating the charge-collection efficiency from the measured values of {tau}{sub oc}/{tau}{sub sc} and the light intensity dependence of {tau}{sub oc}.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC36-83CH10093
• OSTI ID: 335255
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 5 Vol. 103; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
CHARGE COLLECTION
DYES
EFFICIENCY
MATHEMATICAL MODELS
SOLAR CELLS
SPECTROSCOPY
THEORETICAL DATA
TITANIUM OXIDES