Influence of donor substitution at D-π-A architecture in efficient sensitizers for dye-sensitized solar cells: first-principle study

Using density functional theory and time-dependent density functional theory, we theoretically studied a new series of five novel metal-free organic dyes, namely D1-D5, for application in dye-sensitized solar cells based on donor-p-spacer-acceptor (D-pi-A) groups. In this present study, five different donor groups have been designed based on triphenylamine-stilbene-cyanoacrylic acid (TPA-St-CA). The electronic structures, UV-visible absorption spectra and photovoltaic properties of these dyes were investigated. Different exchange-correlation functionals were used to establish a proper methodology procedure for calculation and comparison to experimental results of dye TPA-St-CA. The TD-WB97XD method, which gives the best correspondence to experimental values, is discussed. The calculated results reveal that the donor groups in D2 and D3 are promising functional groups for D-pi-A. In particular, the D2 dye showed small energy levels and red-shift, negative Delta G(inject), fastest regeneration and largest dipole moment and exciton binding energy when compared with TPA-St-CA.