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Interface Stability of a TiO 2 /3‐Methoxypropionitrile‐Based Electrolyte: First Evidence for Solid Electrolyte Interphase Formation and Implications
Author(s) -
Flasque Miguel,
Van Nhien Albert Nguyen,
Swiatowska Jolanta,
Seyeux Antoine,
Davoisne Carine,
Sauvage Frédéric
Publication year - 2014
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300904
Subject(s) - electrolyte , triiodide , chemistry , chemical engineering , nucleation , solvent , iodide , interphase , dye sensitized solar cell , x ray photoelectron spectroscopy , materials science , inorganic chemistry , organic chemistry , electrode , biology , genetics , engineering
We report an in‐depth study focusing on the stability of a benchmark electrolyte composition based on a low‐volatile 3‐methoxypropionitrile (MPN) solvent employed in dye‐sensitized solar cells. In the presence of TiO 2 , the semi‐conductor surface plays a catalytic role in the thermal degradation of the electrolyte, which induces, among other effects, the nucleation and growth of a uniform solid electrolyte interphase (SEI) layer that wraps TiO 2 . On the basis of our actual understanding, we argue that SEI formation is responsible for triiodide depletion in the electrolyte during ageing and also has a simultaneous impact on TiO 2 optoelectronic properties through the onset of a visible‐light absorption tail, energy modification of intraband trap states, and the induction of an increase in both electron lifetime and transport time in TiO 2 . In‐depth characterization of this layer by using XPS and ToF‐SIMS indicates that the chemical composition of this SEI results from solvent and additive degradation, that is, iodide, sulfur, cyano, nitrogen, carbon, and imidazolium rings. The SEI thickness, its content, and the concentration profile strongly vary depending on the ageing conditions. The outcome of this new finding is discussed in comparison with literature observations and stresses the difficulties in reaching long‐term stability at 85 °C by using MPN‐based electrolytes unless new interfacial engineering is accomplished to impede pinholes between dye molecules on TiO 2 .