Photoabsorption-enhanced dye-sensitized solar cells using localized surface plasmon of gold nanoparticles with 16-mercapto hexadecanoic acid

When localized surface plasmon on the surface of metal nanoparticles (Ag, Au, etc.) is excited by light, the irradiated light is scattered and absorbed on the surface of these nanoparticles, and an evanescent wave with a strong electromagnetic field (often called an "optical near field") is generated on their surface. Here, to improve the photocurrent of dye-sensitized solar cells (DSSCs), Au nanoparticles modified with 16-mercapto hexadecanoic acid (AuNP) were inserted into a TiO₂ nanoporous film using a colloidal solution. AuNP was used here because it seems to be more stable than Ag nanoparticles in the electrolyte solution of DSSCs. Considering the overlap between dye and AuNP in their photoabsorption spectrum, a black dye that has photoabsorption over a wide range of wavelength was used in this study. The effect of photoelectrode thickness on the performance of DSSC with AuNP was investigated. The photoelectric conversion efficiency even for a DSSC with a 15-μm-thick photoelectrode, which had the absorbance higher than 2, was improved from 2.41~2.67 to 3.68~3.98% by the addition of AuNP. The plasmon effects due to scattering and to the strong electric field in the DSSC were discussed using the diameter of AuNP, the Haze ratio, the conformation of the carbon chain of AuNP.