Abstract. Magnesium oxide (MgO) nanostructures were synthesized by microwave-assisted
thermal oxidation at various amount of activated carbon additive. The MgO nanostructures were
characterized by scanning electron microscopy (SEM), Transmission electron microscopy (TEM),
X-ray diffractrometry (XRD) and UV-Visible spectroscopy, respectivly. It was observed that, the
obtained MgO have nanocube shape. The MgO nanostructures were applied as a blocking layer in
ZnO dye-sensitized solar cells (DSSCs). The photovoltage, photocurrent, and power conversion
efficiency characteristics of DSSCs were measured under illumination of simulated sunlight
obtained from a solar simulator with the radiant power of 100 mW/cm2. The DSSCs with MgO
layer exhibited higher current density, open circuit voltage and photoconversion efficiency than
those without MgO layer The optimum power conversion efficiency (PCE) was 2.49 % with short
circuit current density (Jsc) of 6.61 mA/cm2, the open circuit voltage (Voc) of 0.66 V and the fill
factor (FF) of 0.59, respectively.