Enhanced photovoltaic performance of photoanodes based on Eu-doped ZnO nanowire arrays for dye-sensitized solar cells

Eu-doped ZnO nanowire (NW) arrays were grown on fluorine-doped tin oxide (FTO) substrates with assistance of hexamethylenetetramine (HMTA) and polyethylenimine (PEI) through Mannich reactions and used as photoanodes for dye-sensitized solar cells (DSCs). Structural characterizations indicate the Eu ions have been incorporated into the ZnO crystalline lattice. An overall light-to-electricity conversion efficiency (η) of 2.64 % was achieved for the DSC based on the 6 % Eu-doped ZnO NW array under AM 1.5 G illumination, and this η was found to significantly increase compared with that of the DSC with undoped ZnO NW array as the photoanode (2.01 %). Meanwhile, the fill factor (FF) of the DSC was upgraded from 63.2 to 78 %. Furthermore, the enhanced electron injection and transport abilities of Eu-doped ZnO NW arrays based on the DSC were revealed by the incident photon-to-electron conversion efficiency (IPCE) spectrum. This research demonstrates an effective way to resolve the low efficiency of DSCs due to the FF drop as well as a great potential for the expanding practical application of rare earth metals.