Photo-Physical Investigations of Ionic Liquid (IL) Based ZnO Dye Sensitized Solar Cells

In this research work, we describe the preparation process, characterization, and photo-physical studies of an ionic liquid (IL) based semiconductor Zinc Oxide (ZnO) nanoparticles synthesized by an economical wet chemical precipitation method. For the first time, an IL was synthesized with the help of a chemical reaction between triethylamine (TEA) and bromoacetic acid (BAA). A polyamide dye was prepared by a reaction between two monomers, ethylenediamine (EDA) and trimesoylchloride (TMC), under room temperature conditions. The polyamide dye was capped on ZnO nanoparticles, and the final product was divided into three different samples, A, B, and C, according to level of concentrations of IL and Polyamide dye. These samples were characterized with X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Dynamic Light Scattering (DLS) spectra, Ultraviolet-Visible (UV-Vis), and Fluorescence spectroscopies. The formation of polyamide linkages in the ionic liquid has been confirmed by a spectroscopic method using Fourier Transform Infrared (FTIR) spectroscopy. The capping of polyamide dye molecules on the surface of ZnO nanoparticles revealed two things: (i) improved UV absorption spectra and (ii) enhanced luminescence in the photoluminescence spectra. Hence, during investigations, broad absorption bands were observed at peaks 263 nm, 278 nm, and 276 nm respectively for samples A, B, and C. Further, IL was used as an electrolyte or redox mediator and polyamide as a dye material in the fabrication of ZnO Dye-Sensitized Solar Cells (DSSCs). The samples A, B, and C were used in the fabrication of photo-anode assemblies for ZnO DSSCs. The ZnO DSSCs were tested under strong simulated light at Air Mass (AM) 1.5 solar irradiations. The observed photovoltaic results shown that solar cell SCB generated a maximum power conversion efficiency (η) of 5.65%, higher than the power conversion efficiencies of solar cells SCA (3.99%) and SCC (4.46%) respectively. The Incident Photon to Current Conversion Efficiency (IPCE) spectra values of ZnO DSSCs shown a significant improvement in the incident photon to current conversion efficiency of solar cell SCB (IPCE=61%) as compared to SCC (enhanced by 6%) and SCA (enhanced by 4%). Such solar cell assemblies can be suitable for green and clean energy applications.