Role of anchoring groups on the light harvesting and optoelectronic properties of triphenylamine derivatives: insights from theory

BACKGROUND

In the present work, DFT and time-dependent DFT calculations were performed to investigate the role of anchoring groups on the photophysical properties and reveal structure-property correlations of triphenylamine (TPA) derivatives. The selected anchoring groups are tetrazole, acrylamide, hydantoin, and rhodanine.

RESULTS

Our results show that the different anchoring groups employed alter the planarity, intramolecular charge transfer properties, and HOMO-LUMO gap and hence influence the optoelectronic properties of the dyes. Although all molecules fulfill the basic requirements with suitable energy levels, band gap, absorption, and charge transfer properties, the dye with rhodanine acceptor (TPA4) was the most promising candidate due to its lowest HOMO-LUMO gap, red-shifted highest λ_max absorption value, better ICT pattern, low total reorganization energy, and good electron injection properties. Overall, it is anticipated that the results of this investigation will point to new avenues for the experimental fabrication of remarkably effective metal-free organic dyes for solar cell applications.

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.

Co-sensitization of the HD-2 complex with low-cost cyanoacetanilides for highly efficient DSSCs

The photophysical and electrochemical properties of new targeted 2-cyanoacetanilide-based dyes are illustrated. New cyanoacetanilides SA7-10 were synthesized and employed as co-sensitizers in DSSCs. The chemical structures of these 2-cyanoacetanilides differ according to the substituent at the benzene ring (-H, -Me, -OMe and -NEt2), with the anchoring moiety being the same, a -COOH group. Furthermore, a density functional theory (DFT) calculation has shown an effective intermolecular charge transfer character, the HOMOs of SA7-10 are mainly located on the corresponding donor part, and their LUMOs are located on carboxylic acid moieties as the acceptor. Interestingly, using photosensitizers SA7-10 as co-sensitizers with HD-2 dye causes an improvement in their photovoltaic performances. Among the dyes, SA10 co-sensitized with HD-2 displayed an overall efficiency of 8.25%, a JSC of 19.5 mA cm-2, a VOC of 0.65 V and an FF of 64.35 compared to 7.46%, 19 mA cm-2, 0.64 V and 60.54, respectively, of HD-2 only. Moreover, the electrochemical impedance spectroscopy (EIS) data of SA7-10 and HD-2 were found to be in accordance with the obtained photovoltaic parameters. Finally, the results indicated that 2-cyanoacetanilide-based dyes were utilized as promising co-sensitizers due to their easy preparation methods and their relatively small size.

Structural studies and photovoltaic investigation of indolo[2,3-b]quinoxaline-based sensitizers/co-sensitizers achieving highly efficient DSSCs

Novel organic sensitizers were designed and synthesized by employing indolo[2,3-b]quinoxaline (IQ) as the main building block. IPCE graphs indicated that both competition and compensation of photon harvesting co-exist during the co-sensitization.

Simple thiophene-bridged D-π-A type chromophores for DSSCs: a comprehensive study of their sensitization and co-sensitization properties

Herein, we report the design and synthesis of four new thiophene-bridged D-π-A configured organic dyes T1-4 comprising different donors, π-spacers and anchoring units, as potential sensitizers and co-sensitizers for DSSCs. The current work also highlights their structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies, including evaluation of their structure-property relationships. The optical results revealed that the dyes T1-4 display λabs and λemi in the range of 402-461 nm and 556-575 nm, respectively, with a bandgap in the order of 2.31-2.58 eV. Furthermore, the results showed that the dyes possess all the pre-requisites to act as sensitizers/co-sensitizers. Among the tested dyes, the device based on sensitizer T2 achieved the highest PCE compared to the other three dyes, under the standard conditions. Furthermore, their co-sensitized devices were fabricated by co-adsorbing them with the well-known Ru-based MH-12 sensitizer and interestingly the co-sensitizer T3 carrying an alkoxy group and a barbituric acid anchor displayed the highest PCE of 8.79%, which is much higher than that of MH-12 alone (8.18%). Conclusively, the study furnishes a deeper understanding of the intricacies involved in the structural modification of sensitizers/co-sensitizers in achieving an enhanced performance of the devices.