Influence of donor substitution at $$\mathrm{D}{-}\uppi {-}\mathrm{A}$$ 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– $$\uppi $$ -spacer–acceptor ( $$\mathrm{D}{-}\uppi {-}\mathrm{A}$$ ) 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 $$\mathrm{D}{-}\uppi {-}\mathrm{A}$$ . In particular, the D2 dye showed small energy levels and red-shift, negative $$\Delta {G}_{\mathrm{inject}}$$ , fastest regeneration and largest dipole moment and exciton binding energy when compared with TPA–St–CA.