Stepped Light-Induced Transient Measurements of Photocurrent and Voltage in Dye-Sensitized Solar Cells:  Application for Highly Viscous Electrolyte Systems

• Published in: Langmuir 2005-11, Vol.21 (23), p.10803-10807
• Main Authors: Nakade, Shogo, Kanzaki, Taisuke, Wada, Yuji, Yanagida, Shozo
• Format: Article
• Language: English
• Subjects: Chemistry; Coloring Agents - chemistry; Electric Power Supplies; Electrolytes - chemistry; Exact sciences and technology; General and physical chemistry; Sunlight; Viscosity
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la051257j

To measure electron diffusion coefficients (D) and electron lifetimes (τ) of dye-sensitized solar cells (DSC), we introduced stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV), which can simplify the optical setup and reduce measurement time in comparison to conventional time-of-flight and frequency-modulated measurements. The method was applied to investigate the influence of the viscosity of a thermally stable high-boiling-point solvent on the energy conversion efficiency of DSCs. By systematic study of the influence of the viscosity, the species of cations as the counter charge of I-/I3 -, and the concentrations of electrolytes, we concluded that a lower dye cation reduction rate due to slower iodine diffusion is a limiting factor for a highly viscous electrolyte system. On the other hand, comparable values of D and increased values of τ were observed in a highly viscous electrolyte. By employing 0.5 M TBAI and 0.05 M I2 in propylene carbonate, the efficiency of the DSC became comparable to that of a DSC using conventional electrolytes consisting of LiI, imidazolium iodide, and 4-tert-butylpyridine in methoxyacetonitrile. The simultaneous evaluation of D and τ through the appropriately simple measurement realizes fast optimization of the efficient and reliable DSC composed of thermally stable but often viscous electrolytes.