Abstract

Electronic Absorption Spectra of Platinum (II) complexes used for Sensitized Solar Cells: DFT/TDDFT Study

Author(s): S Brahim

Using the time dependent density functional theory, we studied in this work the electronic absorption spectra of a series of heteroleptic complexes the form [M(dppf)L] [where dppf =1,10-bis(diphenylphosphino)ferrocene, M=Pt and L= p-tolylsulfonyl dithiocarbimate, p-CH3C6H4SO2NCS2 (1). M=Pt and L= p-chlorobenzene sulfonyl dithiocarbimate, p-ClC6H4SO2NCS2 (2). M=Pt and L= p-bromobenzene sulfonyl dithiocarbimate, p-BrC6H4SO2NCS2 (3). M=Pt and L= 1-ethoxycarbonyl-1- cyanoethylene-2,2-dithiolate(ecda). These complexes have been synthesized and characterized experimentally using the spectroscopy methods (IR, 1H, 13C and 31P NMR and UV-Vis) and crystal X-ray diffraction. Due to their photo-physical and photochemical properties, they have been used as photo sensibilisator in the DSSC (Dye Sensitized Cell Solar). The conversion efficiency of DSSC is defined by the ability of the electron transport, cheap fabrication, flexibility and intense absorption in the visible region of the spectrum. In order to find dyes satisfying these restrictions, many experimental researches have been done to synthesize and to analyze different molecules. In this sense, the Pt (II) complexes quoted above have been selected as efficient photosensitizer because they have shown the best conversion efficiency. In this work, our contribution to study these complexes is set theorical spectra from quantinum calculation. For each complex the contribution is made in two main steps. The first is a geometry optimization to find the optimal structure with the density functional theory (DFT). We using the hybrid functional B3LYP and PBE0, using 6-31G (d,p) and 6-31+G(d) basis as implemented in Gaussian09. The study of HOMO, LUMO has been used to explicate information about charge transfer in molecules. Lastly, from the frontier molecular orbitals we elucidate the UV-vis spectra and electronic absorption proprieties. The calculated spectrums have been compared with the experimental result.