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Resonant Raman study of dye instability in dye‐sensitized TiO 2 system: The effect of surface states
Author(s) -
Wu Kunjie,
Shen Kai,
Liu Weifeng,
Wu Liuer,
Wang Deliang
Publication year - 2012
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201127729
Subject(s) - dye sensitized solar cell , electrolyte , open circuit voltage , materials science , instability , raman scattering , raman spectroscopy , photochemistry , short circuit , chemical engineering , analytical chemistry (journal) , chemistry , optics , voltage , electrode , electrical engineering , physics , organic chemistry , mechanics , engineering
The most critical problem in commercialization of the dye‐sensitized solar cell (DSSC) is its long‐term stability. Many factors contribute to the instability of a DSSC. In order to clarify the role of the surface defects on the cell instability, we modified the TiO 2 surface chemical states, fabricated DSSCs with a very simple structure, and carried out resonant Raman scattering to monitor the dye degradation under open‐circuit condition. The results showed that the dye stability was very sensitive to the TiO 2 surface states. The dye degradation can be described by an exponential decay law. The oxygen vacancy–Ti 3+ chemical state enhanced the recombination of electron with the oxidized electrolyte, i.e ., the electron in the TiO 2 conduction band injected back to the electrolyte, and consequently enhanced the dye regeneration rate by I − , which came from the reduction of ${\rm I}_{3}^{- } $ with electrons. Under the open‐circuit condition the dye stability was increased when it was attached to a TiO 2 surface with a relatively high percentage of oxygen vacancy–Ti 3+ chemical state. The increased electron recombination occurred at the TiO 2 /electrolyte interface resulted in a much decreased open‐circuit voltage and short‐circuit current in a DSSC.