A dye-sensitized solar cell (DSSC) consists of photoelectrode, dye sensitizer, and electrolyte. Among them, electrolytes mainly play the role of transporting charges and regenerating dyes in DSSCs. The composition, content, electrical conductivity and hole transport rate of the electrolyte have a very important influence on the performance of DSSC. Ionic liquids are salts that are completely composed of ions and appear liquid at room temperature (generally not exceeding 25°C). Compared with organic solvents, ionic liquids have the advantages of non-volatility, good thermal and chemical stability, good solubility, easy encapsulation, large electrochemical window, and strong designability. Ionic liquid electrolytes are composed of redox pairs, ionic liquids and additives. As a new type of solar cell, DSSC with ionic liquid as electrolyte has the advantages of safety and stability, simple cell preparation process, easy large-scale industrial production, green and pollution-free, and low production cost, which promotes the large-scale application of DSSC devices.
Figure 1. Imidazole-based ionic liquids for DSSC
- Electrolyte of DSSC: Ionic liquids are liquids composed entirely of ions. In general, the molecular formula of ionic liquids is an asymmetric structure formed by relatively small inorganic anions and relatively large organic cations, and has strong controllability. The basic requirements for DSSC ionic liquids are: (1) stable to water and air; (2) low viscosity and low melting point; (3) high electrical conductivity; (4) good stability. For DSSC ionic liquid electrolytes, it is very important to use a low viscosity ionic liquid system. On the one hand, reducing the apparent viscosity of the original high viscosity electrolyte can increase the physical diffusion of the electrolyte. On the other hand, the addition of low-viscosity ionic liquids also reduces the concentration of electrolyte redox pairs and reduces the charge exchange rate. This allows the electrolyte to better achieve a balance between physical diffusion and charge exchange diffusion during the diffusion process. Common ionic liquids used as DSSC electrolytes are imidazole-based ionic liquids. Replacing the organic solvent in the electrolyte with a non-volatile, high-conductivity ionic liquid in DSSC is beneficial to improve the life and stability of the battery, and has broad application prospects.
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