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

Abstract 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 ( $$\:{q}_{\text{CT}}$$ , $$\:{d}_{\text{CT}}$$ ) were evaluated at the CAM-B3LYP/LANL2DZ level using C-PCM solvation, while Multiwfn characterized wavefunction density differences. Interfacial chemisorption on anatase TiO 2 (101) was simulated using GGA/PBE-DNP on a $$\:{\left({\text{TiO}}_{2}\right)}_{36}\:$$ cluster model. For baseline dyes I–X , amino (-NH 2 ) donor substitution reduces the HOMO–LUMO gap (E g ) and alters orbital alignment. Target dyes XI and XII exhibit significantly narrowed HOMO–LUMO gaps $$\:({E}_{g}=3.68{-}3.70\text{\:eV}$$ in THF), intensified Q-band light-harvesting efficiency (LHE Q = 0.88), enhanced charge transfer $$\:{q}_{\text{CT}}=0.47{-}0.48\hspace{0.17em}e$$ , $$\:{d}_{\text{CT}}=3.10{-}3.17\text{ A}^\circ$$ ), and remarkably low internal reorganization energies ( $$\:{\lambda\:}_{i}=0.319{-}0.377\text{ eV}$$ ), accelerating Marcus interfacial electron injection kinetics. Furthermore, dyes XI and XII demonstrate exothermic bidentate bridging chemisorption ( $$\:\varDelta\:{E}_{\text{ads}}=-15.21\text{ to }-16.71\text{ kcal/mol}$$ ) with strong orbital coupling across the semiconductor interface. These findings establish a predictive computational framework for high-efficiency porphyrin photosensitizers.