Effect of Co2+ Doped Seed Layer on Morphology and Photoelectric Properties of ZnO Nanoarray

Abstract

ZnO nanoarray were synthesized by hydrothermal method on Co2+-doped Zn1-xCoxO (x（mol%）=0.00, 0.01, 0.02, 0.03, 0.04, 0.05) seed layers pre-coated on ITO substrate. The effects of different Co2+ doping concentrations on morphology and photoelectric properties of ZnO nanoarray including transient photo-current and charge transfer resistance were investigated. The addition of Co2+ in the seed layer could perfect the oriented growth of ZnO nanoarray and apparently enhance its photo current. FESEM observation confirmed that the ZnO nanoarray were grown in the way perpendicular to ITO substrate along the direction of (002). Meanwhile, UV-vis tests shown that the band gap energy was decreased from 3.37 eV to 3.16 eV due to Co2+ doping and the ZnO nanoarray had a strong visible region in the range 400-650 nm. The transient photo-current was found to vary from 0.005 to 0.15 mA/cm2 under AM 1.5G simulated sunlight illumination. Photoelectric properties was correlated with the recombination of photo-generated charge carriers, which was inhibited with optimal Co2+ doping concentrations and was beneficial for application in perovskite solar cells.