Structural and electronic study of iron-based dye sensitizers for solar cells using DFT/TDDFT

Rational Design of Broadly Absorbing Boron Dipyrromethene-Carbazole Dyads for Dye-Sensitized Solar Cells: A DFT Study

Structure engineering of boron dipyrromethene (BODIPY) organic dye, to increase its light-harvesting efficiency in dye-sensitized solar cells, has been the subject of rigorous research recently. Herein, we report on the rational designing of BODIPY-carbazole (D-π-A-A) dyads using density functional theory (DFT). The structure of BODIPY-carbazole was first modified by substituting an electron-donating -N(CH3)2 group at the electron-rich carbazole moiety, and two electron-accepting -COOH groups at the BODIPY core. The DFT calculations showed a significant lowering of the band gap from 2.9 eV (pristine BODIPY-carbazole dyad) to 1.87 eV (modified BODIPY-carbazole dyad). Further modification was demonstrated by the incorporation of heterocyclic rings such as thiophene (denoted as D1T), furan (D1F), and phosphole (D1P) into BODIPY-carbazole moiety, which red-shifted the light absorption spectra and consequently improved the light-harvesting efficiency of the dyes. The interactions at the dye/semiconductor interface were studied by employing their bridged-bidentate adsorption models over the titanium dioxide (TiO2)38 nanocluster. Results suggested that the electrons can be efficiently injected from the lowest unoccupied molecular orbital (LUMO) of dyes into the conduction band of TiO2. Among the three dyads, D1P exhibited superior photovoltaic performance with a maximum power conversion efficiency of 13.50%, a short-circuit current density (J sc) of 27.2 mA·cm-2, and an open-circuit voltage (V oc) of 731 mV. The structurally configured new D1P dye can be used as a potential alternative photosensitizer for high-performance dye-sensitized solar cells.

Exploring the effect of oxygen-containing functional groups on the water-holding capacity of lignite

Graphene oxide with different degrees of oxidation was prepared and selected as a model compound of lignite to study quantitatively, using both experiment and theoretical calculation methods, the effect on water-holding capacity of oxygen-containing functional groups. The experimental results showed that graphite can be oxidized, and forms epoxy groups most easily, followed by hydroxyl and carboxyl groups. The prepared graphene oxide forms a membrane-state as a single layer structure, with an irregular surface. The water-holding capacity of lignite increased with the content of oxygen-containing functional groups. The influence on the configuration of water molecule clusters and binding energy of water molecules of different oxygen-containing functional groups was calculated by density functional theory. The calculation results indicated that the configuration of water molecule clusters was totally changed by oxygen-containing functional groups. The order of binding energy produced by oxygen-containing functional groups and water molecules was as follows: carboxyl > edge phenol hydroxyl >epoxy group. Finally, it can be concluded that the potential to form more hydrogen bonds is the key factor influencing the interaction energy between model compounds and water molecules.