Hierarchical architecture of CuInS2 microsphere thin films: altering laterally aligned crystallographic plane growth by Cd and V doping†
The hierarchical architecture of pristine and cadmium (Cd) and vanadium (V) doped copper indium disulphide (CuInS2 (CIS)) microsphere thin films grown on spray coated seed layers by a wet chemical method is demonstrated. First, nano-flakes of self-assembled porous (NFSAP)-CIS microspheres have been optimized on a CIS seed layer by controlling the synthesis strategy. Later, Cd and V were incorporated as foreign impurity ions into the NFSAP-CIS microspheres. The pristine and doped CIS microsphere films resulted in a body-centered-tetragonal crystal structure which was confirmed from the XRD and SAED patterns. The electron microscope images clearly depict the formation of a solid and an elongated NFSAP-CIS microsphere under Cd and V doping, respectively. The change in morphological structure was attributed to the suppression and expansion of the laterally oriented crystallographic plane. The chemical composition and optical and electrical properties of the pristine and Cd and V doped CIS films were determined by UV-vis, photoluminescence, XPS, and Hall measurements. The Cd and V doped CIS microsphere films have superior photoelectric response compared to the pristine CIS films. The controlled laterally oriented crystallographic plane in CIS microspheres brought about by doping induces the modification in the surface morphological structure that results in improved electrical and photo-physical properties. The results of this study provide a framework for fabricating an optimized CIS absorber layer in photovoltaic devices.