Theoretical investigation of phenothiazine-triphenylamine-based organic dyes with different π spacers for dye-sensitized solar cells

A study on indolo[3,2,1-jk]carbazole donor-based dye-sensitized solar cells and effects from addition of auxiliary donors

Density functional theory has been employed to study indolo[3,2,1-jk]carbazole donor-based dyes, incorporating one and two units of 2,4-dimethoxybenzene auxiliary donors. Electrostatic potential analysis highlights the dye with one auxiliary donor (D2) as having the highest charge-donating capability. Structural analysis shows that auxiliary donors enhance planarity, reduce steric hindrance, and improve π-conjugation. Highest occupied molecular orbital (-6.025 to -5.660 eV) and lowest unoccupied molecular orbital (-2.927 to -2.844 eV) of all dyes support efficient electron injection into the semiconductor and dye regeneration process. Auxiliary donors enhance chemical reactivity parameters, improving the suitability of these dyes for dye-sensitized solar cells (DSSCs). Inclusion of extra donors reduces the excitonic binding energy, minimizing recombination losses, and increases polarization, enhancing the charge injection efficiency. Additional analyses explored properties such as charge separation, charge transfer length, transition density matrix and non-covalent interactions. All dyes exhibit strong absorption (410-440 nm) in the visible region, confirming their applicability to DSSCs, while emission spectra provide insights into their fluorescence lifetimes. D2 demonstrates improved performance in specific properties. However, D3, with two auxiliary donors, achieves the best overall balance across other computed parameters. Indeed, the inclusion of auxiliary donors induces significant changes and may be considered as a valuable strategy for designing efficient DSSCs.

The Impact of TPA Auxiliary Donor and the π-Linkers on the Performance of Newly Designed Dye-Sensitized Solar Cells: Computational Investigation

The efficiency of the newly designed dye-sensitized solar cells (DSSCs) containing triphenylamine, diphenylamine (TPA), phenothiazine, and phenoxazine as donors and triazine, phenyl with D₁-D₂-π-linker-π-(A)₂ architecture has been investigated using density functional theory (DFT) and time-dependent (TD-DFT) methods. These methods were used to investigate the geometrical structures, electronic properties, absorption, photovoltaic properties, and chemical reactivity. Furthermore, the calculated results indicate that different architectures can modify the energy levels of HOMO and LUMO and reduce the energy gap. The absorption undergoes a redshift displacement. This work aims at calculating the structural geometries and the electronic and optical properties of the designed dyes. Furthermore, the dye adsorption characteristics, such as the optoelectronic properties and the adsorption energies in the TiO₂ clusters, were calculated with counterpoise correction and discussed.

Theoretical study of T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer for DSSCs

Eight novel T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer were designed, and the geometries, electronic structures, and optical features of these isolated dyes and dye-(TiO₂)₉ systems were investigated with density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. Some quantify factors influencing the energy conversion efficiency (PCE) such as the light harvesting efficiency (LHE), electron injection driving force (ΔG_inject) and dye regeneration driving force (ΔG_reg) were also calculated for dye-sensitized solar cells (DSSCs) applications. It is found that these dyes show a good performance of electron injection and dye regeneration owing to the proper value of ΔG_inject and ΔG_reg. The optimized geometries of the non-planar molecular configuration of donor and the planar structure of the naphthalimide conjugated bridge are beneficial to efficient intramolecular charge transfer and the suppression of molecular aggregation. The properties about the electronic structure and absorption spectra indicate that replacement of benzene with thiophene unit near to cyanoacetic acid acceptor can generate more efficient conjugation effect and achieve red shift of absorption spectra, resulting a higher J_sc and V_oc in DSSCs device. The theoretical results reveal that DTPH2, DTPH4, DTCA2 and DTCA4 would be used as potential sensitizers for DSSCs applications.

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).

The number density effect of N-substituted dyes on the TiO2 surface in dye sensitized solar cells: a theoretical study

The bulky of the donor moiety reduces the number density of the adsorbed Dye3 on the surface dramatically, corresponding to poorer energy conversion efficiency of 3.91% in Dye3 compared to the significantly better performance of 5.45% in Dye2.