Al-doped ZnO film as a transparent conductive substrate in indoline-sensitized nanoporous ZnO solar cell

We have deposited porous ZnO films on aluminum-doped ZnO (ZnO/AZO) and fluorine-doped tin oxide (ZnO/FTO) transparent substrates, and annealed both in air at 500°C. X-ray diffraction measurements of the nanoporous ZnO films after heat treatment showed that, ZnO/AZO film exhibited a dominant (002) diffraction while the ZnO/FTO showed mixed diffraction peaks with the (100) and (101) being dominant. Dye-sensitized solar cells (DSC) based on the sensitization of the porous ZnO films on AZO and FTO substrates with an indoline dye were constructed. The photoaction spectrum, which is a measure of the degree of sunlight harvesting, was broad and higher in the ZnO/AZO DSC than that of the ZnO/FTO DSC. Conversion efficiency of 7.3% was obtained for the ZnO/AZO DSC while 4.5% was recorded for the ZnO/FTO. The superior photovoltaic performance of the ZnO/AZO DSC is attributed to better ZnO film orientation after thermal treatment and the higher sunlight harvesting.