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The present work describes the effect of structural modification of carbazole‐based photosensitizers carrying carboxylic acid as a common anchoring functionality, on the photovoltaic parameters of newly fabricated DSSCs. In this study, we have selected our previously reported three carbazole‐based derivatives, viz. S1‐3 having different structural designs, that is, D‐π‐A (S1), D‐D‐π‐A (S2), and A‐π‐D‐π‐A (S3) with different donor units and π‐spacers, but an identical cyanoacetic acid anchoring unit. We have evaluated their optical, electrochemical, and photovoltaic behaviors in order to explore their structure‐property relationships. Also, the theoretical investigations were performed to obtain a deeper understanding of their HOMO‐LUMO levels, charge distribution in FMOs, directional flow of electrons within the push‐pull type sensitizers, and optical behavior. Finally, the DSSCs were constructed by employing these dyes as sensitizers without any co‐absorbents and the performance of the devices was evaluated by using illuminated current‐voltage characteristics. Among the tested dyes, di‐anchoring S3 exhibited improved PCE of 3.77 % due to its strong adsorption on the TiO2 surface that resulted in superior VOC of the cell. While the S2 containing electron‐releasing anisole as an auxiliary donor exhibited better JSC value leading to the optimum PCE of 3.73 % which is comparable to that of S3. Obviously, these results validate the role of the π‐spacer and additional donor of the sensitizers on the overall performance of the DSSCs. [ABSTRACT FROM AUTHOR]

Herein, we report the development of two new low-cost 9-(2-ethylhexyl)-9Hcarbazoles carrying the mono/dimethoxyphenyl substituted cyanovinylene units symmetrically at 3- and 6-positions of the carbazole core (CZ1-2), as potential hole-transporting materials (HTMs) for perovskite solar cell (PSC) application. The current work highlights their structural, photophysical, electrochemical, theoretical, and photoelectrochemical studies, including evaluation of their structure-property relationships. Evidently, the optical studies showcased their excellent fluorescence ability due to their push-pull natured structure; their λabs and λemi values were found to be in the order of 410-430 nm and 530-560 nm, respectively, with a bandgap in the range of 2.5-2.6 eV. Further, their theoretical studies, performed by using the DFT simulations clearly revealed in-depth information on their molecular geometries, FMO, and electronic properties. Finally, new PSCs were fabricated successfully by employing CZ1-2 as HTMs to evaluate their photovoltaic performances. Their results indicated that the device with CZ1 displayed enhanced PCE of 2.55% (JSC = 7.85 mA/cm2, VOC = 0.79 V and FF = 40%) than the cell with CZ2 (PCE = 1.71%, JSC = 8.15 mA/cm2, VOC = 0.4 V, FF = 49%) and the obtained data are well comparable with reference, Sipro- OMeTAD (PCE = 4.76%, JSC = 12.27 mA/cm2, VOC = 0.84 V, FF = 45%). Conclusively, the study furnishes a deeper understanding of the intricacies involved in the structuralmodification of in low-costHTM in achieving an enhanced performance of the devices. [ABSTRACT FROM AUTHOR]

The main objective of our present investigation includes the design synthesis and characterization of two novel D-π-A configured carbazole based dyes C1-2, carrying two different anchors and the same donor system. In the new design, a simple O-alkylated phenyl group as a donor scaffold, cyanovinylene and thiophene group serve as a π-spacer, while cyanoacetic acid, barbituric acid units function as electron acceptor/ anchoring units. The newly synthesized compounds were characterized by FTIR, NMR spectroscopic techniques including the elemental analysis. Further, their optical properties were investigated by using UV-visible, fluorescence spectrophotometer. In addition, the Density functional theory (DFT) calculations were performed to get their electron distribution in FMO levels. In order to investigate their photovoltaic characteristics, the synthesized dyes were employed as sensitizers towards the fabrication of DSSC's. The device fabricated with dye C1 displayed better PCE of 1.2 % with JSC of 3.64 mA·cm-2, VOC of 0.50 V and FF of 65 % than other dye C2. These experimental results provide a better understanding and deeper insight into the intricacies involved in the design of superior sensitizers to further improve the performance of DSSCs. [ABSTRACT FROM AUTHOR]

Herein we report the molecular design, synthesis, and inclusive investigation of four novel di-anchored symmetric dyes (CP 1-4) centered on electron deficient cyanopyridine scaffold as possible photosensitizers for DSSC application. These new chromogens (CP 1-4) comprise a powerful electron-withdrawing cyanopyridine moiety linked with additional electron attracting functionalities such as cyanoacetic acid (CP 1), 3-(carboxymethyl) rhodanine (CP 2), 2,4,6-pyrimidinetrione (CP 3), and 2,6-dihydroxy-2-mercaptopyrimidine (CP 4), as effective acceptor/anchoring units via biphenyl donor units. Their in-depth optical and electrochemical behaviour were investigated to assess their suitability as photosensitizers. Further, the molecular modeling calculations were undertaken to understand their ground state properties and energy level potentials. The comprehensive studies revealed that they own all the requisites to performance as a potential photosensitizer for DSSC application. Four new metal-free novel di-anchored cyanopyridine-centered symmetric dyes (CP 1-4) were successfully designed, synthesized, and fully characterized as possible sensitizers. Further, the experimental results revealed that these push-pull type dyads own all the prerequisites to act as a potential photosensitizer on TiO 2 for DSSC application. [Display omitted] • Designed and synthesized new di-anchored cyanopyridine-centered symmetric dyads (CP 1-4). • Evaluated their optical and electrochemical properties to assess suitability as sensitizers. • Performed DFT studies to gauge their HOMO-LUMO energy levels. • The ESP maps advocates favoring charge movements, hence they are promising sensitizers. [ABSTRACT FROM AUTHOR]