Tuning the physical properties of organic sensitizers by replacing triphenylamine with new donors for dye sensitized solar cells - a theoretical approach

Synthesis and characterization of a new phenothiazine-based sensitizer/co-sensitizer for efficient dye-sensitized solar cell performance using a gel polymer electrolyte and Ni–TiO2 as a photoanode

Efficiency enhancement of a DSSC using a metal-free co-sensitizer, Ni–TiO2 photoanode, and blend gel polymer electrolyte.

Tuning optoelectronic properties of triphenylamine based dyes through variation of pi-conjugated units and anchoring groups: A DFT/TD-DFT investigation

Dye-sensitized solar cells (DSSCs) have attracted widespread attention due to their unique features. In the present work, molecular engineered triphenylamine based dyes featuring donor-bridge-acceptor architecture have been considered and investigated for suitable properties for DSSCs applications. Hydantoin anchoring group has been introduced replacing the commonly used cyanoacrylic acid to improve the long-term stability of the device. Results on the effects of varied anchoring groups and pi-spacers have been interpreted from the viewpoint of DFT/TD-DFT calculations. Designed sensitizers exhibit suitable light-harvesting efficiencies, excited-state lifetimes, electron injection and regeneration abilities. Red-shifted electronic spectra are observed for three hydantoin dyes compared to others in the same family. Further analysis of chemical descriptors and observation from full-electron donor-acceptor map reveal that the three dyes among nine are potential materials with promising properties towards improving DSSCs performance.

DFT/TD-DFT study of novel T shaped phenothiazine-based organic dyes for dye-sensitized solar cells applications

Five novel T shaped phenothiazine-based organic dyes DTTP1~5 with different spacers at N (10) position were designed. The geometries, electronic structures, absorption spectra, electron transfer and injection properties of these isolated dyes and dye/(TiO₂)₉ systems were investigated via density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculation. The optimized geometries indicate that these T shaped dyes show non-planar conformations, which are helpful in suppressing the close intermolecular π-π aggregation in device and enhancing thermal stability. The calculated results indicate that type of π-conjugated spacers can affect the molecular absorption spectra. Introduction of thiophene-benzothiadizole-thiophene unit as π-conjugated spacer can most effectively shift the light absorption to near infrared region and enhance the light harvesting efficiency (LHE). Moreover, it is found that these dyes show a good performance of electron injection and dye regeneration owing to the proper electron injection driving force (ΔG_inject) and dye regeneration driving force (ΔG_reg). The theoretical results reveal that these dyes could be used as potential sensitizers for DSSCs, and DTTP4 would be the most plausible sensitizer for high-efficiency DSSCs due to the narrow HOMO-LUMO energy gap (Δ_H-L), broad absorption spectrum, high LHE value, and large dipole moment (μ_normal).

Theoretical Study of Phenothiazine Organic Dyes with Different Spacers for Dye-Sensitised Solar Cells

In this paper, six organic dyes have been studied by density functional theory (DFT). The electron-acceptor group is the cyanoacrylic acid unit for all sensitisers, and the electron-donor unit is a phenothiazine (PTZ) fragment substituted by an ethynyl-pyrene unit; the π-linker was varied, and the influence was investigated. The dye bearing the divinylthiophene linker showed the highest absorption maximum. The theoretical photovoltaic properties revealed that the overall efficiency of the solar cell could be remarkably improved using the designed dyes. The results indicated that all of the studied organic dyes are good candidates as photosensitisers for dye-sensitised solar cells (DSSCs).

Quantum efficiency of the photo-induced electronic transfer in dye-TiO2 complexes

We present a method based on a time-dependent self-consistent density functional tight-binding (TD-DFTB) approach, able to predict the quantum efficiency of the photoinjection process in a dye-TiO₂ complex from a fully atomistic picture. We studied the process of charge transfer of three systems with different dyes: catechol (CAT), alizarin (ALZ) and FSD101. Each system was excited with lasers of different energies in the range of 300-2500 nm, studying the efficiency of the induced charge transfer process at the incident energies. We show that the perturbation can produce either hole transfer or electron transfer from the dye to the nanoparticle, therefore affecting the efficiency of the charge transfer in the solar cell when illuminated by broadband radiation.

Physical Insight on Mechanism of Photoinduced Charge Transfer in Multipolar Photoactive Molecules

Two series of novel dyes were designed based on the multipolar structures of the red dye D35 and blue dye DB, by introducing the furan (F), benzene ring (B) and benzo[c]thiophene (BT) groups into the conjugated bridge of D35 in proper order and adjusting the position of diketopyrrolopyrrole(DPP) unit and the incorporation of fluorine in the conjugated bridge of DB, respectively. We performed the quantum chemistry calculation to investigate the ground state and excited properties in a direct correlation with the spectra properties and abilities of losing or accepting electron for the original and designed molecules. Furthermore, the absorption spectra characteristics in consideration of the aggregation of dyes on the TiO₂ layer and intermolecular charge transfer rate of the dimers were calculated. The obtained results indicate that the larger intermolecular charge transfer rate leads to the poor photoelectrical properties of the dyes, and the designed dyes D35-3 and DB-2 would exhibit the best photoelectrical properties among the investigated dyes due to their lower energy gaps, widened absorption spectra and prominent charge transfer properties.