Synthesis and application of stilbenoid phenothiazine dendrimers as additives for dye-sensitized solar cells

Abstract

Stilbenoid dendrimers with phenothiazine as a surface group were synthesized in good yields by the Heck and Horner–Wadsworth–Emmons coupling reaction and characterized by spectral and analytical data. Various core units such as trimethylbenzene, pyridine, and triphenylamine with phenothiazine as the surface unit were employed for the synthesis of dendrimers. The photophysical properties of the dendrimers reveal that as the generation increases the light absorption ability also increases. Furthermore, as the generation increases the absorption maxima show a hypsochromic shift for the n–π* transition and a bathochromic shift for the π–π* transition. However, the fluorescence emission in general increases as the dendrimer generation increases. When the synthesized stilbenoid dendrimers are utilized as an additive in the redox couple (I⁻/I₃⁻) of a Dye Sensitized Solar Cell (DSSC), the solar energy conversion efficiency increases with an increase in generation and reaches a maximum of 7.3% with the higher generation dendrimer 10.