Rational design of triphenylamine-based sensitizers for DSSCs: a DFT comparison of pyridine and amine donor substituents

Context

The rational design of metal-free organic sensitizers is critical for developing cost-effective, high-efficiency dye-sensitized solar cells (DSSCs). This study uses density functional theory (DFT) to explore how modifying the triphenylamine (TPA) donor with pyridine rings or amino groups at ortho-, meta-, and para-positions affects the optoelectronic properties of D-π-A sensitizers. Our calculations show that para-position amino substitution (dye N3) yields the most red-shifted absorption (\({\lambda }_{max}\)=523, 50 nm beyond reference dyes), the highest theoretical open-circuit voltage (Voc = 1.77 eV, 0.3 eV higher than others), and enhanced charge transfer efficiency. These findings highlight para-position amines as a promising strategy for optimizing DSSC performance and identify N3 as a prime candidate for synthesis and experimental validation.

Methods

Ground-state geometries, vibrational frequencies, and frontier molecular orbitals were calculated using the M06 functional with the 6-31G(d) basis set, chosen for its accuracy in organic systems. UV–Vis absorption and excited-state properties were predicted via time-dependent DFT (TD-DFT) with the M06-2X functional, optimized for excited-state accuracy, and the 6-31G(d) basis set. Solvation effects in acetonitrile were modeled using the IEF-PCM polarizable continuum model. Calculations were performed with Gaussian 16.