The Halogenation Effects of Electron Acceptor ITIC for Organic Photovoltaic Nano-Heterojunctions.

Molecular engineering plays a critical role in the development of electron donor and acceptor materials for improving power conversion efficiency (PCE) of organic photovoltaics (OPVs). The halogenated acceptor materials in OPVs have shown high PCE. Here, to investigate the halogenation mechanism and the effects on OPV performances, based on the density functional theory calculations with the optimally tuned screened range-separated hybrid functional and the consideration of solid polarization effects, we addressed the halogenation effects of acceptor ITIC, which were modeled by bis-substituted ITIC with halogen and coded as IT-2X (X = F, Cl, Br), and PBDB-T:ITIC, PBDB-T:IT-2X (X = F, Cl, Br) complexes on their geometries, electronic structures, excitations, electrostatic potentials, and the rate constants of charge transfer, exciton dissociation (ED), and charge recombination processes at the heterojunction interface.

Optoelectronic properties of diathiafulvalene-functionalized diketopyrrolopyrrole-fullerene molecular dyad.

Single component molecular dyad donor-acceptor junction is an important type of organic solar cells. Understanding the optoelectronic properties of molecular dyad plays the critical role to develop active layer materials for such kind of solar cells. Here, diathiafulvalene-functionalized diketopyrrolopyrrole-fullerene (DFDPP-Ful) was selected as the representative system, and the geometries, electronic structures and excitation properties of DFDPP-Ful monomer and dimer were systematically investigated based on extensive quantum chemistry calculations.

The bis-dimethylfluoreneaniline organic dye sensitizers for solar cells: A theoretical study and design.

Development of novel dye sensitizers with suitable optoelectronic properties is effective to improve the power conversion efficiency of dye-sensitized solar cells (DSSCs). Considering the effectiveness of conjugate bridges in modification of optoelectronic properties, based on the dye sensitizers C201, C203, C204 and C205, five kinds of organic dye sensitizers are designed with different thiophene-based moieties and the functionalized graphene flakes (GFs) as conjugate bridges. The performances of these dye sensitizers are analyzed in terms of the calculated geometries, electronic structures and excitation properties.

Assessment of Ab Initio and Density Functional Theory Methods for the Excitations of Donor-Acceptor Complexes: The Case of the Benzene-Tetracyanoethylene Model.

The understanding of the excited-state properties of electron donors, acceptors and their interfaces in organic optoelectronic devices is a fundamental issue for their performance optimization. In order to obtain a balanced description of the different excitation types for electron-donor-acceptor systems, including the singlet charge transfer (CT), local excitations, and triplet excited states, several ab initio and density functional theory (DFT) methods for excited-state calculations were evaluated based upon the selected model system of benzene-tetracyanoethylene (B-TCNE) complexes. On the basis of benchmark calculations of the equation-of-motion coupled-cluster with single and double excitations method, the arithmetic mean of the absolute errors and standard errors of the electronic excitation energies for the different computational methods suggest that the M11 functional in DFT is superior to the other tested DFT functionals, and time-dependent DFT (TDDFT) with the Tamm-Dancoff approximation improves the accuracy of the calculated excitation energies relative to that of the full TDDFT.

The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation.

Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures.

The adsorption of α-cyanoacrylic acid on anatase TiO2 (101) and (001) surfaces: a density functional theory study.

The adsorption of α-cyanoacrylic acid (CAA) on anatase TiO2 (101) and (001) surfaces, including adsorption energies, structures, and electronic properties, have been studied by means of density functional theory calculations in connection with ultrasoft pseudopotential and generalized gradient approximation based upon slab models. The most stable structure of CAA on anatase TiO2 (101) surface is the dissociated bidentate configuration where the cyano N and carbonyl O bond with two adjacent surface Ti atoms along [010] direction and the dissociated H binds to the surface bridging O which connects the surface Ti bonded with carbonyl O. While for the adsorption of CAA on (001) surface, the most stable structure is the bidentate configuration through the dissociation of hydroxyl in carboxyl moiety.