This review discusses recent progress and the rational design criteria used in the structural design of organic dyes and porphyrin photosensitizers for DSSCs. The effects of molecular structural engineering on the photophysical and electrochemical properties, photovoltaic parameters, and efficiency of DSSCs are presented.
A new series of 4-hexyl-4H-thieno[3,2-b]indole (HxTI) based organic chromophores is developed by structural engineering of the electron donor (D) group in the D-HxTI-benzothiadiazole-phenyl-acceptor platform with different fluorenyl moieties, such as unsubstituted fluorenyl (SGT-146) and hexyloxy (SGT-147), decyloxy (SGT-148) and hexyloxy-phenyl substituted (SGT-149) fluorenyl moieties. In comparison to a reference dye SGT-137 with a biphenyl-based donor, the effects of the donating ability and bulkiness of the fluorenyl based donor in this D-π-A-structured platform on molecular properties and photovoltaic performance are investigated to establish the structure-property relationship. The photovoltaic performance of dye-sensitized solar cells (DSSCs) is improved according to the bulkiness of the donor groups. As a result, the DSSCs based on SGT-149 show high power conversion efficiencies (PCEs) of 11.7% and 10.0% with a [Co(bpy) 3 ] 2+/3+ (bpy = 2,2′-bipyridine) and an I − /I 3 − redox electrolyte, respectively. Notably, the co-sensitization of SGT-149 with a SGT-021 porphyrin dye by utilizing a simple "cocktail" method, exhibit state-of-the-art PCEs of 14.2% and 11.6% with a [Co(bpy) 3 ] 2+/3+ and an I − /I 3 − redox electrolyte, respectively.
A new class of multifunctional polymers based on poly(l,6heptadiyne) derivatives with various functional groups such as carbazole unit for photoconductive polymers and nonlinear optical (NLO) chromophores for NLO polymers were synthesized by metathesis polymerization. The polymerizations were carried out with MoCI,-and WCI,-based catalysts. The catalytic activity of MoCI, was found to be greater than that of WCI , . The resulting polymers exhibited photoconductivity and large optical nonlinearity. These conjugated polymers have good solubility in common organic solvents, long-term stability toward air oxidation, and high electrical conductivity.
Highly efficient counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) were developed using thin films of scalable and high-quality, nitrogen-doped graphene nanoplatelets (NGnP), which was synthesized by a simple two-step reaction sequence. The resultant NGnP was deposited on fluorine-doped SnO2 (FTO)/glass substrates by using electrospray (e-spray) coating, and their electrocatalytic activities were systematically evaluated for Co(bpy)3(3+/2+) redox couple in DSSCs with an organic sensitizer. The e-sprayed NGnP thin films exhibited outstanding performances as CEs for DSSCs. The optimized NGnP electrode showed better electrochemical stability under prolonged cycling potential, and its Rct at the interface of the CE/electrolyte decreased down to 1.73 Ω cm(2), a value much lower than that of the Pt electrode (3.15 Ω cm(2)). The DSSC with the optimized NGnP-CE had a higher fill factor (FF, 74.2%) and a cell efficiency (9.05%), whereas those of the DSSC using Pt-CE were only 70.6% and 8.43%, respectively. To the best of our knowledge, the extraordinarily better current-voltage characteristics of the DSSC-NGnP outperforming the DSSC-Pt for the Co(bpy)3(3+/2+) redox couple (in paticular, FF and short circuit current, Jsc) is highlighted for the first time.
Edge‐selectively fluorinated graphene nanoplatelets (FGnPs) are prepared by mechanochemically driven reaction between fluorine gas (20 vol% in argon) and activated carbon species from graphitic C–C bonds unzipped by high‐speed stainless steel balls with a high kinetic energy. The fluorination at edges of the unzipped graphene nanoplatelets (GnPs) is confirmed by various analytical techniques while the content of fluorine in FGnPs is determined to be 3.0 and 3.4 at% by X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectroscopy, respectively. Because of the large difference in electronegativity between carbon (χ = 2.55) and fluorine (χ = 3.98) and the strong C–F bond, the edge‐fluorination of GnPs can provide the maximized charge polarization with an enhanced chemical stability. Thus, electrodes based on the resultant FGnPs demonstrate superb electrochemical performance with excellent stability/cycle life in dye‐sensitized solar cells (FF: 71.5%; Jsc: 14.44 mA cm−2; Voc: 970 mV; PCE: 10.01%) and lithium ion batteries (650.3 mA h g−1 at 0.5 C, charge retention of 76.6% after 500 cycles).
Nitrogen fixation is essential for the synthesis of many important chemicals (e.g., fertilizers, explosives) and basic building blocks for all forms of life (e.g., nucleotides for DNA and RNA, amino acids for proteins). However, direct nitrogen fixation is challenging as nitrogen (N2) does not easily react with other chemicals. By dry ball-milling graphite with N2, we have discovered a simple, but versatile, scalable and eco-friendly, approach to direct fixation of N2 at the edges of graphene nanoplatelets (GnPs). The mechanochemical cracking of graphitic C−C bonds generated active carbon species that react directly with N2 to form five- and six-membered aromatic rings at the broken edges, leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb catalytic performance in both dye-sensitized solar cells and fuel cells to replace conventional Pt-based catalysts for energy conversion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.