Synthesis of nanocrystalline ZnO powder via sol–gel route for dye-sensitized solar cells

This paper reports the growth mechanism of sol–gel-derived nanocrystalline ZnO powder. The influence of pH value of the sol on the crystallite size, morphology and structure of ZnO powder was investigated by using X-ray diffraction, transmission and scanning electron microscopy. Maximum size nanocrystallite (∼14 nm) of ZnO powder was obtained for pH value of 9. An increase in the band gap (blue shift) was observed with decrease in the size of the ZnO nanocrystallites. The variation in band gap was found to be in agreement with theoretical calculations using effective mass model. The growth mechanism of ZnO particles from zinc acetate dihydrate precursor by the sol–gel process has been discussed in terms of solvation, hydrolysis and polymerization. The synthesized ZnO powders were successfully used as the electrode material for dye-sensitized solar cells.