Effect of π-Spacer Length in Novel Xanthene-Linked l-(D−π–A)2-Type Dianchoring Dyes for Dye-Sensitized Solar Cells

The effect of thiophene π-spacer length was studied in xanthene-linked l-(D−π–A)2-type dianchoring dye performance in dye-sensitized solar cells. The photophysical, electrochemical, and photovoltaic performances of KS-19 with single thiophene and KS-21 with dithiophene units as π-spacers were compared. The overall result showed that the presence of an extra thiophene unit in KS-21 led to the extension of conjugation, causing broadening and a red-shift of light absorption which in turn resulted in increased JSC and power conversion efficiency (PCE).