Synthesis and Characterization of Al Doped ZnO Nanorods by Hydrothermal Method for DSSC Applications

Abstract

In the forthcoming times solar energy is viewed as a key participant among all environmentally friendly energy sources. As the sun is providing energy continuously, the scientific community is looking for cost effective, environmentally friendly and highly efficient methods distribute and store solar energy. In this thesis, ZnO nanorods (NRs) and Al doped ZnO (AZO) NRs (different concentration of Al) are synthesized using hydrothermal method. Photo electrodes are fabricated using undoped ZnO NRs, 2% and 4% Al dopped ZnO NRs using hydrothermal method on seed layer precoated with ZnO using dip-coating method for undoped ZnO NRs 2% and 4 % Al-doped ZnO NRs on FTO glass substrate. Prepared samples were characterized using different techniques such as Field Emission Scanning Electron Microscope (FE-SEM) and UV-Vis spectroscopy. SEM analysis showed increase in diameter and length along with increase in spacing between ZnO NRs due to Al doping. The diameter of the NRs vairy from 20 nm to 250 nm and their lengths were increased from 300 nm to 2 micron was observed. For undoped ZnO NRs the average diameter is approximately 30 nm and average length was 300 nm. For 2% Al-doped ZnO NRs the approximate diameter is 100 nm with average length of NRs is of 1 micron and for 4% Al-doped ZnO NRs the diameter of the NRs appears to be ~250 nm having average length of 2 micron. UV-Vis reveal the absorption spectrum for Undoped, 2% Al-doped and 4% Al-doped ZnO NRs. The results reveal that the 4% Al-doped ZnO NRs show maximum absorption and minimum transmission having least bandgap of 3.03 eV calculated using Tauc plot. Moreover, photovoltaic performance was investigated using J-V curves. For undoped ZnO NRs based DSSC produce short-circuit current density (J_sc) of 2.0139 mA/cm2, open circuit voltage (V_oc) of 0.709 V, fill-factor (FF) of 0.5497 and power conversion efficiency (η) of 0.78% while for 2% AZO NRs based DSSC produce J_scof 2.6357 mA/cm2, V_oc of 0.736 V, FF of 0.5565 and efficiency of 1.07% and 4% AZO NRs based DSSC produce J_sc of 2.837 mA/cm2, V_ocof 0.723 V, FF of 0.574 and efficiency of 1.17%. Results indicate that power conversion efficiency is maximum for 4% Al-doped ZnO NRs due to larger spacing between prepared NRs. J-V curve show max efficiency of 1.17% for 4% Al-doped ZnO.