Characterization and microstructure study of Eriochrome black T- Co (II)- PVA composite film for photovoltaic application

Abstract Film of Eriochrome black T (EBT) and CoCl2 doped with polyvinyl alcohol (PVA) was synthesized by casting technique from their solution. X-ray diffraction peaks for EBT indicates a poly-crystalline structure with random grains orientation of orthorhombic type structure. However, crystallinity of the EBT powder was lost completely on complexation in EBT-Co(II)-PVA composite, showing a glassy behavior. The morphology of surface for composite film is rough, showing irregular grains with nanowire of PVA attached to many grains. FT-IR spectroscopy suggested that the geometrical shape of the EBT-Co(II)-PVA complex is 5-coordinate geometrical structure. Differential and thermogravimetric analysis indicated that Co(II)-PVA chains are well coupled within EBT powder. Furthermore, EBT showed a semiconducting like behavior below 300 K while at higher temperature, EBT showed a metallic like behavior with resistivity values lower than that of the EBT-Co(II)-PVA composite film. 1H-NMR and electron spin resonance (ESR) were investigated. A film of structure Au/EBT-CoCl2.6H2O-PVA/Al was fabricated and studied for photovoltaic cell applications. High rectification characteristic and photovoltaic parameters were determined from current-voltage curves under dark and illumination. The results supports EBT can be developed for the applications in thermistor material for electronics and solar cells.