Bandgap Engineering in Doped ZnO Nanostructures for Dye Sensitized Solar Cell Applications

Pure ZnO and dZnO (doped ZnO) systems of type Zn_1−x M _x O (M = Co, Cu, Fe and Mn) synthesised by co-precipitation method were evaluated for DSSC studies. Tween-80, a non-ionic surfactant which was used during preparation process also acted as binder for coating the nanoparticles on the FTO glass plate. In order to reduce the band gap, transition metal dopants have been incorporated into ZnO so that it changes the photo electrochemical properties. The conduction band edge minimum (CBM) potentials and valence band edge maximum (VBM) potentials were calculated. The CBM and VBM potentials varied with different dopants. The band gap were engineered such that it shifts the conduction band minimum (CBM) to less negative potential than LUMO (Lower Unoccupied Molecular Orbital) of the dye (Rhodamine B). Pure ZnO showed highest open circuit voltage (V _oc) of 631.7 mV and short-circuit current density (J _sc) of 3.5031 μA/cm². In case of dZnO, 5% doping showed highest short-circuit current density and highest power conversion efficiency for all dopants (Co, Cu, Fe and Mn). Nanoparticles with remarkable morphologies influence the efficiency of dye sensitized solar cell (DSSC). The DSSC parameters such as open circuit voltage (V _oc), short-circuit current density (J _sc), Fill factor (FF) and photovoltaic efficiency (η) was calculated. The effect and variation of CBM and VBM in DSSC parameter are discussed.