High Open-Circuit Voltage Solid-State Dye-Sensitized Solar Cells with Organic Dye

Solid-state dye-sensitized solar cells were fabricated using an organic dye, 2-cyanoacrylic acid-4-(bis-dimethylfluoreneaniline)dithiophene (JK2), which exhibits more than 1 V open-circuit potential (V-oc). To scrutinize the origin of high voltage in these cells, transient V-oc decay measurements and density functional theroy calculations of the interacting dye/semiconductor surface were performed. A negative conduction band shift was observed due to the favorable dipolar field exerted by the JK2 sensitizer to the TiO2 surface, at variance with heteroleptic Ru(II)-dyes for which an opposite dipole effect was found, providing an increased V-oc.