Facile synthesis of Cr doped hierarchical ZnO nano-structures for enhanced photovoltaic performance

Transition metal doped ZnO has been widely used in various research areas such as optoelectronics, chemical sensors, solar cells and photo catalysts. Herein, we fabricated Cr-doped ZnO nanospheres by a facile solvothermal treatment for enhanced photovoltaic performance. A systematic study of the structural and optical properties of Cr doped ZnO were investigated by scanning electron microscopy (SEM), X-ray diffraction technique (XRD), Ultra violet-Visible spectroscopy (UV–Vis) respectively. XRD patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peaks, which suggests that Cr ions replaces the regular Zn sites in the ZnO crystal structure. Furthermore, doped ZnO nanospheres were employed in the hybrid solar cells in combination with P3HT and gave better current densities than their corresponding undoped counterparts. The increase in solar cell efficiency of doped ZnO nanospheres is solely due to the improvement in the charge separation efficiency in the 4% Cr doped ZnO nanospheres. Optoelectronic analysis of the Cr doped ZnO hybrid solar cell showed comparable results of J_SC −3.7 (mAcm⁻²), V_OC 0.44 (V), Fill Factor 0.49 and Efficiency (ƞ) 0.79 (%). The enhanced photovoltaic activity of the Cr doped hierarchical ZnO nanostructures provides an interesting grounds for the design and enhancement of the low cost, feasible synthesis of photovoltaic nanostructure materials.