Propping the optical and electronic properties of potential photo-sensitizers with different π-spacers: TD-DFT insights

The influence of the position and quantity of thiophene or acetylene groups on the photoelectric properties of dye-sensitized solar cells

To investigate the influence of the position and quantity of thiophene or acetylene groups on the photoelectric properties of dye-sensitized solar cells (DSSCs), density functional theory (DFT) were employed to simulate five zinc porphyrin dye molecules (T-3, T-3-D, T-3-A, T-3-AD, and T-3-ace). The optimized geometry indicated that T-3-ace possessed superior planar properties, attributed to incorporating the acetylene groups, facilitating the charge transfer process. The lower lowest unoccupied molecular orbital (LUMO) energy levels of T-3-ace and T-3-D suggested that introducing thiophene or acetylene groups on the donor side enhanced the electron absorption capability of the dyes. The analysis of optical properties revealed that the incorporation of thiophene or acetylene groups on the donor side (T-3-D or T-3-ace) exhibited a more prominent red shift and a broader absorption range, which was beneficial for promoting electron excitation and optical properties. The low reorganization energy suggested these two molecules have better structural stability during photoexcitation. The prediction of photoelectric conversion efficiency (PCE) showed that introducing thiophene was beneficial for improving the PCE, with the most significant effect observed when introducing thiophene groups on the donor side (T-3-D). The T-3-ace demonstrated the highest maximum short circuit current density Jmax; however, the lower electron injection efficiency (φinject) led to a lower short circuit current density JSC and consequently a lower PCE. This work is conducive to providing valuable insights into the molecular structure of zinc porphyrin dyes and their photoelectric properties.

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 s c of 5.480 mA·cm−2, V o c of 0.582 V, η of 2.151% larger than R with J s c of 1.826 mA·cm−2, V o c 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 ( μ n o r m a l ) were calculated, and the shift of conduction band edge of a semiconductor (ΔECB) has been analyzed, which has a close relationship with J s c and V o c . The results demonstrated that, due to the higher LHE, τ, μ n o r m a l , and red-shifted absorption peak, Q has better photoelectric properties than R as a promising sensitizer.

A first-principles roadmap and limits to design efficient supercapacitor electrode materials

A road map to guide researchers to predict the desired properties is presented based on the DFT calculations to allow researchers decide which property of the material they wish to predict or develop and how to choose the proper DFT route to do so.

Photoactuated Properties of Acetylene-Congeners Non-Metallic Dyes and Molecular Design for Solar Cells

This paper theoretically simulated (using DFT and TD-DFT in N,N-dimethylformamide (DMF) solvent) the photodynamic properties of three non-metallic dye molecules with D-π-A₁-π-A₂ structure. The total photoelectric conversion efficiency (PCE) could be evaluated by the following parameters: the geometric structures, the electronic structures, and the absorption spectra, the analyses of charge difference density (CDD) and natural bond orbitals (NBO), the analyses of ionization potential (IP) and electron affinity (EA) from electronic contribution capacity, the reorganization energies (λh, λe, and λtotal), and the chemical reaction parameter (h, ω, ω−, and ω+) for intramolecular charge transfer (ICT) processing, the excited lifetime (τ) and the vertical dipole moment (μnormol). The ∆Ginject, the ∆Gdyeregen, the light harvesting efficiencies (LHE) and the excited lifetime (τ) were used to explain experimental JSC. The experimental trend of VOC was explained by the calculation of ∆ECB and μnormol. Moreover, the 15 dyes were designed by adding the electron-donor groups (–OH, –NH₂, and –OCH₃) and the electron-acceptor groups (–CF₃, –F, and –CN) to the LS-387 molecular skeleton, which improved electronic contribution, intramolecular charge transfer (ICT), and optoelectronic performance.