Structure–Property Analysis of Thiophene‐Substituted Triphenylamine‐Based Photosensitizers for DSSC Applications

ABSTRACT

One of the main constituents of a dye sensitized solar cell (DSC) that influences its efficiency to transform solar energy into electricity is the photosensitizer or the dye. Accordingly, the choice of donor, π‐bridge and the acceptor is very crucial while designing the dye's architecture. In this work, the influence of one additional donor in the basic D‐π‐A structure of thiophene‐substituted triphenylamine‐donor based organic dye (metal free) has been investigated. Dyes having D‐π‐A and D‐D′‐π‐A architecture were designed. In the dyes with D‐D′‐π‐A architecture, one donor, thiophene‐substituted triphenylamine (D) was kept fixed while the other (D′) was varied to study the effect of the additional donor in a linear chain. Two π‐spacers were used to design 10 molecules. Geometry, charge transfer and optoelectronic properties of the proposed molecules have been studied. For this, the dyes were adsorbed on the nanocrystalline surface of the semiconductor (TiO ₂ ). Theoretical evaluation of various parameters such as energies of frontier molecular orbitals, energy gap between HOMO and LUMO, wavelength of maximum absorbance, electron affinity, ionization potential and photovoltaic parameters has been done in this work using density functional theory (DFT) and time dependent density functional theory (TD‐DFT) methods. Among the studied dye molecules, maximum efficiency of 5.3% at J _SC  = 15 mA cm ⁻² is shown by the dye CB. As it is well known that the device's efficiency depends on photovoltaic parameters, these can be augmented by small variation in the geometry of dye as indicated by this study.