Application of Chlorophyll as Sensitizer for ZnS Photoanode in a Dye-Sensitized Solar Cell (DSSC)

Abstract

Zinc sulphide thin films have been synthesized by the electrodeposition method onto stainless steel substrate followed by dipping in acetone solution of chlorophyll in different time intervals to form photosensitised thin films. The photoelectrochemical parameters of the films have been studied using the photoelectrochemical cell having the cell configuration as follows \( {\rm{photoelectrode/NaOH}}\left({1\;{\rm{M}}} \right) + {\rm{S}}\left({1\;{\rm{M}}} \right) + {\rm{N}}{{\rm{a}}_2}{\rm{S}}\left({1\;{\rm{M}}} \right){\rm{/C}}\,\,\left({{\rm{graphite}}} \right)\). The photoelectrochemical characterization of the semiconductor film and dye-sensitised films has been carried out by measuring current–voltage (I–V) in the dark, power output and photoresponse. The study proves that the conductivity of both ZnS film and dye-sensitised ZnS films are n-type. The power output curves illustrate that open circuit voltage (Voc) and short circuit current (Isc) increase from 0.210 V to 0.312 V and from 0.297 mA to 0.533 mA, respectively. The fill factor initially decreases from 0.299 to 0.213 and then increases to 0.297 irregularly whereas efficiency increases from 0.047% to 0.123%. The UV–Vis absorbance spectrum of chlorophyll in acetone shows the presence of chlorophyll. The structural morphology of the ZnS thin films has also been analysed by using x-ray diffraction technique (XRD) and a scanning electron microscope (SEM). The XRD pattern shows the formation of nanocrystalline ZnS thin films of size 65 nm and the SEM images confirm the formation of fibrous film of ZnS. The energy diffraction analysis of x-ray confirms the formation of ZnS thin films.