Advancing dye sensitized solar cell efficiency and computational insights into porphyrin based dyes

A comparative density functional theory (DFT) and time-dependent DFT (TD-DFT) study was conducted on twelve tetraphenylporphyrin sensitizers (I-XII), including five free-base/zinc complex pairs and two novel asymmetric dyes (XI, XII) modeled from the benchmark GY50 framework, to evaluate their potential for dye-sensitized solar cells (DSSCs). Electronic structures, vertical excitations, and spatial charge-transfer metrics ([Formula: see text], [Formula: see text]) were evaluated at the CAM-B3LYP/LANL2DZ level using C-PCM solvation, while Multiwfn characterized wavefunction density differences. Interfacial chemisorption on anatase TiO₂(101) was simulated using GGA/PBE-DNP on a [Formula: see text]cluster model. For baseline dyes I-X, amino (-NH₂) donor substitution reduces the HOMO-LUMO gap (E_g) and alters orbital alignment. Target dyes XI and XII exhibit significantly narrowed HOMO-LUMO gaps [Formula: see text]in THF), intensified Q-band light-harvesting efficiency (LHE_Q = 0.88), enhanced charge transfer [Formula: see text], [Formula: see text]), and remarkably low internal reorganization energies ([Formula: see text]), accelerating Marcus interfacial electron injection kinetics. Furthermore, dyes XI and XII demonstrate exothermic bidentate bridging chemisorption ( [Formula: see text]) with strong orbital coupling across the semiconductor interface. These findings establish a predictive computational framework for high-efficiency porphyrin photosensitizers.