Development of functional organics materials for high efficient dye sensitized solar cell: a challenge for sustainable alternative energy

In this research, the structure and energetic properties of sensitizer for dye-sensitized solar cell were investigated, the ground-state structure of all molecules were fully optimized using density functional theory (DFT) method. Optimized structures were then be used to calculate excitation energy (Eg), maximum absorption wavelength (max), and oscillator strength () in dichloromethane solvent (CH2Cl2), by applying Time-Dependent Density Functional Theory (TDDFT). Furthermore, the adsorption complexes of dyes on the TiO2 anatase (101) surface were carried out by mean of the periodic calculation. The optical properties and electron-injection characteristics from dyes to the TiO2 surface are then computed by TDDFT method. The D--A structural system is the basis of metal-free dyes owing to its effective photoinduced intramolecular charge transfer properties. Moreover, in order to possess broad and intense spectral absorption in the visible light region, one strategy for optimizing dye structure is to introduce more -conjugation linker between the donor and acceptor, Another strategy is to incorporate a donor-donor moiety into the framework, D-D--A structural system, resulting in stronger electron-donating ability but also greater steric hindrance, which can prevent unfavorable dye aggregation. However, more bulky of the donor moiety could reduce the number density of the adsorbed dye on the TiO2 surface. In addition, increase conjugated bridge between the donor and acceptor units and auxiliary acceptor to farm a D--A--A and D-A--A frameworks owing to the expended conjugation. It was found that a system can improve light harvesting efficiency. Furthermore, we also study in the effect of substitution position of anchoring groups on indole derivatives. It was found that the effect of substitution position of anchoring groups on indole ring affected to the absorption properties of dyes molecule. In conclusion, it has been shown that these computational tools described above can provide the detailed characterizations which are in agreement with experimental efficiency and therefore can be of valuable help in further design of novel organic sensitizer for higher efficiency of photovoltaic device.