Photovoltaic behavior of K-doped ZnO nanorods synthesized by a facile electrochemical route

Well-aligned K-doped zinc oxide (ZnO) nanorods were successfully grown on a FTO substrate using a cost-effective facile electrochemical route. The structural and morphological results indicated the single-crystalline structure of all samples with preferential growth along the c-axis direction. The K doping in the ZnO lattice dramatically influenced the bowing in the valence band edge resulting in the band gap reduction and increased the optical absorption. According to the optical results, the incorporation of K+ ions as the donors into ZnO lattice substantially modulated the bandgap structure of ZnO nanorods leading to formation of new emission centers. This in turn resulted in the redshift of the ultraviolet emission peaks. The optical band gap reduces from 3.26 eV for the undoped ZnO to 3.21 eV for K (10 wt%)-doped ZnO nanorods. The high conversion efficiency of approximately 4.34% is attained for 6 wt% K-doping contents. The good photovoltaic behavior of the K (6 wt%)-doped ZnO nanorods can be attributed to the higher surface-to-volume ratio and the large K-doped ZnO nanorods/FTO interfacial band bending. The findings indicated that K doping of the ZnO nanostructures significantly affects the dye-sensitized solar cells performance.