Light harvesting and optical-electronic properties of two quercitin and rutin natural dyes

The photovoltaic properties of two dyes (quercitin (Q) and rutin (R)) were experimentally investigated. The results showed that Q had excellent photoelectric properties with J_sc of 5.480 mA·cm^-2, V_oc of 0.582 V, η of 2.151% larger than R with J_sc of 1.826 mA·cm^-2, Voc of 0.547 V, and η of 0.713%. For a better understanding of the photoelectric properties of two molecules and illustrating why the performances of Q is better than R from the micro-level, the UV-VIs spectrum, Fourier transforms infrared (FT-IR) spectrum, and cyclic voltage current characteristics were experimentally investigated. What is more, density functional theory (DFT) and time dependent density functional theory (TD-DFT) have been implemented in theoretical calculation. Based on the calculated results, frontier molecular orbitals (FMOs), charge differential density (CDD), infrared vibration, first hyperpolarizability, projected density orbital analysis (PDOS), electrostatic potential (ESP), and natural bond orbital (NBO) were analyzed. Hole/electron reorganization energies (λ_h/λ_e), light harvesting efficiency (LHE), fluorescent lifetime (τ), absorption peak, and the vertical dipole moment (μnormal) were calculated, and the shift of conduction band edge of a semiconductor (δE_CB) has been analyzed, which has a close relationship with J_sc and V_oc. The results demonstrated that, due to the higher LHE, τ, μnormal, and red-shifted absorption peak, Q has better photoelectric properties than R as a promising sensitizer.