Interface stability of a TiO₂/3-methoxypropionitrile-based electrolyte: first evidence for solid electrolyte...

Area of Science:

• Materials Science
• Electrochemistry
• Photovoltaics

Background:

• Dye-sensitized solar cells (DSSCs) are a promising photovoltaic technology.
• Electrolyte stability is crucial for long-term DSSC performance.
• 3-methoxypropionitrile (MPN) is a low-volatile solvent used in DSSC electrolytes.

Purpose of the Study:

• To investigate the stability of MPN-based electrolytes in DSSCs.
• To understand the role of the TiO2 semiconductor surface in electrolyte degradation.
• To characterize the solid electrolyte interphase (SEI) layer formed during ageing.

Main Methods:

• In-depth stability study of a benchmark MPN-based electrolyte.
• Analysis of electrolyte degradation catalyzed by TiO2.
• Characterization of the SEI layer using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

Main Results:

• The TiO2 surface catalyzes electrolyte thermal degradation, forming a uniform SEI layer.
• SEI formation leads to triiodide depletion and alters TiO2 optoelectronic properties (absorption, trap states, electron transport).
• SEI composition includes iodide, sulfur, cyano, nitrogen, carbon, and imidazolium rings, varying with ageing conditions.

Conclusions:

• SEI formation is a key factor limiting the long-term stability of MPN-based DSSCs at 85°C.
• Interfacial engineering is required to prevent SEI-related issues and achieve stable DSSC operation.
• Understanding SEI formation is critical for advancing DSSC technology.