Hole-induced polymerized interfacial film of polythiophene as co-sensitizer and back-electron injection barrier layer in dye-sensitized TiO₂ nanotube array

In this work, we demonstrate that an ultra-thin film of polythiophene deposited interfacially via hole-induced polymerization on the surface of dye-sensitized TiO₂ nanotube array acts as co-sensitizer, and hinders back-electron transfer in a DSSC. Consequently, the dark current, and the recombination reactions can be suppressed, leading to an improved number of electron density at the TiO₂ array electrode. Thus, an enhanced photocurrent, and power conversion efficiency of the device is achieved. This logical concept is experimentally justified, and the device, after polythiophene interfacial treatment, demonstrates an enhanced power conversion efficiency by the factor of 39.19%.