Versatility of Photosensitizers in Dye-Sensitized Solar Cells (DSSCs)

Because of their scientific relevance in the field of energy conversion, dye-sensitized solar cells (DSSCs) have become a focus of major studies in the last two decades. At present, DSSC is generally either sensitized with inorganic dyes, metal-free organic dyes, or natural dyes. These dyes have emerged as potential alternatives to costly and scarce Ru-based dyes because of being economical, simple attainability, ease of preparation, and environmental friendliness. The majority of alternatives to Ru-based dyes have so far proved to be inferior to Ru-based dyes due to their fragility, narrow absorption bands, and unfavorable dye aggregation. The present review focuses on recent research about sensitizers comprising inorganic dyes, metal-free organic dyes, and natural dyes for DSSCs. Following the introduction, Section 2 describes the DSSC operation, including the essential operational principles and basic components of a DSSC. Section 3 introduces various photosensitizers used in DSSC, and Section 4 states the conclusion and outlook on the field of DSSC research. It also describes and summarizes related sensitizers and their efficiency.

Synthesis of High-Performance Aqueous Fluorescent Nanodispersions for Textile Printing—A Study of Influence of Moles Ratio on Fastness Properties

Aqueous fluorescent dispersions containing dyed acrylic-based copolymer nanoparticles possess significant credentials concerning green technology as compared to those prepared with the conventional vinyl-based monomers in textile and garment sectors; however, their essential textile fastness properties are yet to achieve. In the present work, a series of acrylic nanodispersions were synthesized by varying the moles ratio of benzyl methacrylate (BZMA), methyl methacrylate (MMA), and 2-hydroxypropyl methacrylate (HPMA) monomers. This was done to study their effect on dye aggregation and dyed polymer particles agglomeration. FT-IR spectral analysis showed the formation of polymer structures, while Malvern Analyzer, Transmission Electron Microscopy, and Scanning Electron Microscopy analysis suggested that the particles are spherical in shape and their size is less than 200 nm. The obtained nanodispersions were later applied on cotton fabrics for the evaluation of wash fastness and colour migration. Premier color scan spectrophotometer and zeta potential measurement studies suggested that colour migration of printed cotton fabrics increased with an increasing agglomeration of particles and it was also observed to increase with the moles ratio of MMA and zeta potentials.

Effect of Chenodeoxycholic Acid as Dye Co-Adsorbent and ZnO Blocking Layer in Improving The Performance of Rose Bengal Dye Based Dye Sensitized Solar Cells

Effective suppression of dye aggregation on the photoanode surface of dye sensitized solar cell plays a key role in improving the solar cell efficiency. Chenodeoxycholic acid (CDCA) is a very popular anti dye aggregation material used in Dye sensitized solar cells. However, the selection of an improper concentration of CDCA may lead to decreased solar cell efficiency by lowering the open circuit voltage and short circuit current as a consequence of reduced dye loading. The influence of chenodeoxycholic acid (CDCA) as a dye co-adsorbent on the performance of DSSCs fabricated using Rose Bengal dye was studied in this paper. The concentration of the CDCA solution was varied to identify the optimum value for the best device performance. Aside from this, the effect of a very thin and compact ZnO blocking layer was also investigated to reduce the recombination. With photovoltaic parameters such as short circuit current density (Jsc) = 1.98 mA/cm2, open circuit voltage (Voc) = 0.58 V, and fill factor (FF) = 0.43, the traditional cell displayed an overall conversion efficiency of 0.50 %, while the power conversion efficiency was found to be increased to 0.97 % ( Jsc = 2.80 mA/cm2, Voc= 0.64, FF = 0.58 ) when CDCA was added at optimised concentration of 8 mM. Reduced dye aggregation and increased electron injection in the presence of CDCA may be accounted for the DSSC's remarkable improvement in efficiency. Moreover, the combined effect of 8 mM CDCA and the compact ZnO blocking layer dramatically enhanced the efficiency further to 1.23 % (Jsc = 3.09 mA/cm2, Voc= 0.66, FF = 60 ). Electrochemical impedance spectroscopic (EIS) analysis revealed that the addition of CDCA as a co-adsorbent in the dye solution and addition of ZnO blocking layer resulted in significantly improved electron lifetime and reduced electron recombination yielding improved Jsc, Voc and η.

Novel Red Light-Absorbing Organic Dyes Based on Indolo[3,2-b]carbazole as the Donor Applied in Co-Sensitizer-Free Dye-Sensitized Solar Cells

Three novel organic dyes (D6, D7 and D8), based on indolo[3,2-b]carbazole as the donor and different types of electron-withdrawing groups as the acceptors, were synthesized and successfully applied in dye-sensitized solar cells (DSSCs). Their molecular structures were fully characterized by 1H NMR, 13C NMR and mass spectroscopy. The density functional theory (DFT) calculations, electrochemical impedance spectroscopy analysis, UV–Vis absorption characterization and tests of the solar cells were used to investigate the photophysical/electrochemical properties as well as DSSCs’ performances based on the dyes. Dye D8 showed the broadest light-response range (300–770 nm) in the incident monochromatic photo-to-electron conversion efficiency (IPCE) curve, due to its narrow bandgap (1.95 eV). However, dye D6 exhibited the best device performance among the three dyes, with power conversion efficiency of 5.41%, Jsc of 12.55 mA cm−2, Voc of 745 mV and fill factor (FF) of 0.59. We also found that dye aggregation was efficiently suppressed by the introduction of alkylated indolo[3,2-b]carbazole, and, hence, better power conversion efficiencies were observed for all the three dyes, compared to the devices of co-sensitization with chenodeoxycholic acid (CDCA). It was unnecessary to add adsorbents to suppress the dye aggregation.

Ultra-Bright Fluorescent Organic Nanoparticles Based on Small-Molecule Ionic Isolation Lattices

Ultra-bright fluorescent nanoparticles hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical co-assembly with cyanostar anion-receptor complexes of associated counterions. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit dye aggregation quenching. We report a simple, one-step supramolecular approach to formulate SMILES materials into nanoparticles. Rhodamine-based SMILES nanoparticles stabilized by glycol amphiphiles show high fluorescence quantum yield (30%) and brightness per volume (5000 M^–1 cm^–1 / nm³) with 400 dyes packed into 16-nm particles, corresponding to an absorption coefficient of 4 × 10⁷ M^–1cm^–1. UV excitation of the cyanostar component leads to highest brightness (>6000 M^–1 cm^–1 / nm³) by energy transfer to rhodamine emitters. Coated nanoparticles stain cells and are thus promising for bioimaging.

Ultra-Bright Fluorescent Organic Nanoparticles Based on Small-Molecule Ionic Isolation Lattices

Ultra-bright fluorescent nanoparticles hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical co-assembly with cyanostar anion-receptor complexes of associated counterions. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit dye aggregation quenching. We report a simple, one-step supramolecular approach to formulate SMILES materials into nanoparticles. Rhodamine-based SMILES nanoparticles stabilized by glycol amphiphiles show high fluorescence quantum yield (30%) and brightness per volume (5000 M^–1 cm^–1 / nm³) with 400 dyes packed into 16-nm particles, corresponding to an absorption coefficient of 4 × 10⁷ M^–1cm^–1. UV excitation of the cyanostar component leads to highest brightness (>6000 M^–1 cm^–1 / nm³) by energy transfer to rhodamine emitters. Coated nanoparticles stain cells and are thus promising for bioimaging.

Effects of alkanolamine solvents on the aggregation states of reactive dyes in concentrated solutions and the properties of the solutions

The solvent, DEA, reduces the dye aggregation that may be caused by the weak hydrogen bonding and relatively smaller steric hindrance effect.