Solid Organic Electrolytes for DSSC Stability
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Solution Overview
Problem
Conventional liquid electrolytes in dye-sensitized solar cells (DSSCs) face issues such as long-term stability, high temperature operation limitations, leakage due to thermal expansion, and chemical degradation of electrodes, which hinder their commercial application.
Innovation Solution
Development of solid organic electrolytes comprising PEGylated and fluorinated imidazolium iodides blended with 1-ethyl-3-methylimidazolium iodide, which are thermally stable and provide high ionic conductivity without the need for liquid solvents or inorganic salts, allowing for efficient ion conduction in DSSCs, electrochromic devices, and lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolytes are used in DSSCs, then high ionic conductivity and power conversion efficiency are achieved, but long-term stability and high temperature operation are compromised
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to solid by using PEGylated and fluorinated imidazolium iodides. This phase transition maintains sufficient ionic conductivity (1.11×10−4 S/cm at 30°C and 2.88×10−3 S/cm at 90°C) while dramatically improving thermal stability and eliminating leakage issues associated with liquid electrolytes.
Solution Approach 2:
The patent creates a composite solid electrolyte system by blending PEGylated imidazolium iodide with fluorinated imidazolium iodide. This composite approach combines the advantages of both components: PEGylation provides high ionic conductivity through ether oxygen coordination, while fluorination enhances thermal stability and reduces viscosity, achieving a balance between conductivity and stability.
2Quantity of substance
If liquid electrolytes are used in DSSCs, then efficient ion conduction is achieved, but leakage due to thermal expansion occurs at elevated temperatures
Solution Approach 1:
The patent exploits the phase transition from liquid to solid state by designing imidazolium iodide compounds with controlled melting points. The solid electrolyte maintains structural integrity at elevated temperatures, preventing leakage while preserving ionic conductivity through the ordered arrangement of ions and PEG chain flexibility.
3Productivity
If liquid electrolytes are used in DSSCs, then high power conversion efficiency is achieved, but chemical degradation of electrodes occurs
Solution Approach 1:
The patent creates a chemically inert solid electrolyte environment using fluorinated imidazolium iodides. The fluorinated groups and solid matrix structure reduce chemical reactivity with electrode materials, preventing degradation while maintaining the I−/I3− redox couple functionality necessary for high power conversion efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solid organic electrolytes exhibit enhanced thermal stability up to 250-300°C, with ionic conductivities of 1.11×10−4 S/cm at 30°C and 2.88×10−3 S/cm at 90°C, overcoming the limitations of liquid electrolytes and enabling stable operation in energy conversion and storage devices.
Implementation Method 1
ionic conductivities of 1.11×10−4 S/cm at 30°C and 2.88×10−3 S/cm at 90°C
Data Source
AI summary
Solid, or highly viscous, organic electrolytes consisting of alkylimidazolium cation with alkyl, PEGylated and fluorinated side chains of different molecular weights were synthesized and characterized (cf. chemical structures in Schemes 1 and 2). The PEGylated/fluorinated imidazolium iodide is a solid organic electrolyte that has a conductivity of about 2×10−5 S/cm at 30° C. The ionic conductivity could be significantly increased (1.11×10−4 S/cm at 30° C. and S/cm at 2.88×10−3 at 90° C.) by blending the PEGylated/fluorinated imidazolium iodide with another solid electrolyte, 1-ethyl-3-methylimidazolium iodide (EtMImI). The PEGylated imidazolium iodides synthesized in the present work have conductivities in the range 1.6×10−4 S/cm to 2×10−4 S/cm at 30° C. and viscosities in the range 620 cP to 720 cP at 30° C. The iodide counter ion in the present electrolytes supplies the anion for the I−/I3− redox mediators for DSSCs. Therefore, the organic electrolytes of the present invention can be used even without the addition of inorganic salts such as LiI or KI. We found that the addition of an organic solid electrolyte, EtMImI, resulted in an increase in the ionic conductivity of the PEGylated/fluorinated imidazolium iodides, whereas the addition of the inorganic LiI led to a decrease in ionic conductivity. All the electrolytes are thermally stable until high temperatures (250° C. to 300° C.).