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Abstract The properties of three D1-π-D2-A dyes with dithiafulvenyl as donor (D1), phenothiazine as ancillary donor (D2), cyanoacrylic acid as acceptor along with different π groups, diphenyl for 1 , dithienyl for 2 , and thiopheneyl-benzothiadiazole for 3 , are studied. Besides the isolated dyes, the monomeric and dimeric adsorptions are also studied by combination of first principle and molecular dynamic simulations. There is no distinct difference among three dyes on the basis of only isolated dyes. When the dye-TiO 2 adsorption is considered, 3 is excluded because of its inferior items. However, it is still a difficult task to differentiate 1 and 2 even if the aggregation effect is included. The fluctuation of 1 is larger than that of 2 during the dynamic simulation resulting in the larger electronic coupling. The aggregation, especially for the aggregation during the dynamic simulation, is necessary to evaluate the performance of organic dye. Additionally, a new D-π-A dye 4 with the identical donor, π-bridge and acceptor is designed to compare with 2. 2 is totally superior to 4 indicating that suitable groups and appropriate configuration are both important to enhance the performance of organic dye. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Aggregation is inevitable for the organic dyes, and it is difficult to evaluate its effects due to its complexity. Herein, we combine first principles and molecular dynamics (MD) simulations to explore the influence of aggregation on the optical and electronic properties for THI-BTZ-2T-C . If only the static properties are considered, the configuration of dye is not varied greatly when the adsorbed dyes are increased from monomer to hexamer. However, the absorption spectrum varies regularly with the increased aggregation order. In addition, the contribution of different orbitals of various atoms to density of states (DOS) gradually increases with the aggregation order increasing. When dynamics simulation is performed, the torsion between different components of dye is enlarged. Meanwhile, the perpendicular model is altered during the dynamics simulations, the dye would like to bend towards the TiO 2 surface. Moreover, the electronic coupling is greatly improved during the molecular dynamics simulations especially for the H-aggregation. The dye aggregation mainly affects the electrons injection process resulting in the reduction of the photoelectric conversion efficiency for dye sensitized solar cells (DSSCs). Reduction of perfect face to face stacking would be an efficient pathway to weaken the aggregation. [ABSTRACT FROM AUTHOR]

Two new indoline-based D-A-π-A dyes, D3F and D3F2 (see Scheme 1), are developed on the basis of the reported D3 by insertion of one or two F atoms on benzothiadiazole group. Our central aim is to explore high-efficiency organic dyes applied in dye-sensitized solar cells by inclusion of a simple group rather than by employment of new complicated groups. The performance of two new designed organic dyes, D3F and D3F2 , is compared with that of D3 from various aspects including absorption spectrum, light harvesting efficiency, driving force, and open-circuit voltage. Besides the isolated dye, the interfacial property between dye and TiO 2 surface is studied. D3F and D3F2 do not show absolute superiority than D3 not only for the isolated dyes but also for the monomeric adsorption system. However, D3F and D3F2 would effectively reduce the influence of aggregation resulting in the much smaller intermolecular electronic coupling. Although the aggregation has attracted much attention recently, it is studied alone in most of studies. To comprehensively evaluate the performance of dye-sensitized solar cells, it is necessary to consider aggregation along with electron injection time from dye into TiO 2 rather than only static items, such as, band gap and absorption region. [ABSTRACT FROM AUTHOR]