Al-doped ZnO thin films grown onto ITO substrates as photoanode in dye sensitized solar cell

The photovoltaic performance of dye sensitized solar cells using Al-doped ZnO thin films (ZnO:Al) grown onto ITO substrates as photoanode and natural dye as sensitizer had been studied. The effects of [Al/Zn] ratio on structural, microstructural, optical and electrical properties of these films were investigated. X-ray diffraction analysis of pure and Al-doped ZnO thin films revealed the polycrystalline nature with wurtzite-type structure and preferential orientation along the c-axis. FESEM images revealed granular and porous nanostructure for lower content of Al, whereas nanosheet morphology for higher Al content. Uniform distribution of grains with columnar-like nanostructure was observed by AFM analysis and confirmed the c-axis orientation. EDAX analysis confirmed the presence of Zn and O along with dopant Al. Higher transmittance around 95% was observed for AZO film (1.5 at.%) in the visible region with an absorption edge around 350 nm, while band gap energy was found to vary in the range 3.26–3.42 eV. PL spectra exhibited a ultra-violet emission centered at 385 nm and an intense violet emission centered at 444 nm. A decrease in the electrical resistivity was noticed upto 1.5 at.% of Al doping and increased for further increase of Al content. Dye sensitized solar cell fabricated with pure and AZO films as photoanodes sensitized with different natural dye extracts showed improved cell performance. © 2016 Elsevier Ltd