In organic solar cells (OSCs), the electron donor (D) and electron acceptor (A) blended active layer is the most crucial component for governing the power conversion efficiency (PCE). Various ...efficient donor materials with wide structural variations have been developed to couple with high-electron mobility fullerene-based acceptors, giving PCEs beyond 12%. However, fullerene-embedded OSCs encounter great challenges of low flexibility for structural modifications, poor absorption and blend morphological stability. The demand for alternative acceptors drives current OSC research towards non-fullerene acceptors (NFAs). Tailor-made NFAs of polymer or small molecule (SM) can typically exhibit tunable optical and electrochemical properties, high solubility, air stability, and favorable intermolecular interactions leading to compact packing and good nano-phase segregation in the active blend. In this review, we systematically depict the effects of molecular structures on the physical properties and device performances. The promising/most popular cores and general molecular design strategies of NFAs are outlined. The polymeric and SM NFAs were classified into several sub-groups based on their structural features, and in every sub-group, the structural evolution, current status, the champion case as well as the future challenges were highlighted and discussed. For polymeric NFAs, naphtalene diimide (NDI) and perylene diimide (PDI) are most promising and widely explored due to their easy synthesis, high electron affinity and mobility, leading to promising PCE when NDI and PDI units are conjugated with various electron-rich/deficient aromatics. Various electron-deficient core-based polymeric NFAs were also employed. Aromatic diimides (NDI and PDI) were also widely employed as the central core or terminal unit for SM NFAs. In particular, PDI was interested in electron deficient core, and their monomers, dimers, and trimers gave various degrees of success. PDI trimeric NFA showed superior PCE (∼9.3%) because of its twisted 3D or fused geometry capable of interlocking the polymer donor allows optimum molecular packing, morphology and, therefore, efficient charge separation and transport. The excellent photochemical stability, strong absorption and synthetic flexibility of diketopyrrolopyrrole (DPP) produced promising SM NFAs. The rigid and co-planar indacenodithiophene (IDT) cores bearing various electron-deficient terminal groups were extensively explored, and the structural engineering on both the core and side chain groups together with post-treatments produced the highest PCE (∼13.2%). These results conclude that NFAs possess the better possibility for tuning absorption profile, matched energy levels and optimal D/A nano-morphology for delivering promising PCEs. We highlighted the structure-property-performance relationships and future challenges, and hope this article can trigger new ideas for designing more promising NFAs.
A new low‐band gap dyad DPP‐Ful, which consists of covalently linked dithiafulvalene‐functionalized diketopyrrolopyrrole as donor and fullerene (C60) as the acceptor, has been designed and ...synthesized. Organic solar cells were successfully constructed using the DPP‐Ful dyad as an active layer. This system has a record power‐conversion efficiency (PCE) of 2.2 %, which is the highest value when compared to reported single‐component organic solar cells.
Climbing alone: The combination of dithiafulvalene‐functionalized diketopyrrolopyrrole (DPP) as donor with fullerene (Ful) as acceptor has been successfully explored. Its utilization in single‐component organic solar cells (SC‐OSCs) was investigated, and it was shown to have a record power‐conversion efficiency. ITO=indium tin oxide.
A series of new metal free organic dyes containing carbazole as donor and π-linker have been synthesized and characterized as effective sensitizers for dye sensitized solar cells (DSSCs). The ...carbazole functionalized at C-2 and C-7 served as electron-rich bridge. The donor property of the carbazole is substantially enhanced on introduction of tert-butyl groups at C-3 and C-6 positions and the oxidation propensity of the dyes increased on insertion of thiophene unit in the conjugation pathway. These structural modifications fine-tuned the optical and electrochemical properties of the dyes. Additionally, the presence of tert-butyl groups on the carbazole nucleus minimized the intermolecular interactions which benefited the performance of DSSCs. The dyes served as efficient sensitizers in DSSCs owing to their promising optical and electrochemical properties. The efficiency of DSSCs utilizing these dyes as sensitizers ranged from 4.22 to 6.04%. The tert-butyl groups were found to suppress the recombination of injected electrons which contributed to the increment in the photocurrent generation (J SC) and open circuit voltage (V OC). A dye with carbazole donor functionalized with tert-butyl groups and the conjugation bridge composed of 2,7-disubstituted carbazole and thiophene fragments exhibited higher V OC value. However, the best device efficiency was observed for a dye with unsubstituted carbazole donor and the π-linker featuring carbazole and bithiophene units due to the high photocurrent generation arising from the facile injection of photogenerated electrons into the conduction band of titanium dioxide (TiO2) facilitated by the low-lying LUMO.
A new thermoreversible organogel based on diketopyrrolopyrrole dye (DPP-NCO) is reported for the first time and evolved as a new building block for the fabrication of 1D supramolecular assembly. AFM ...analysis illustrated that its gel state is composed of different sized 1D rods. DPP-NCO gel used as an additive in organic solar cells yields high efficiency of 7.9% owing to better nanophase separation of its active layer.
New hybrid materials featuring the dipolar fragment 6H-indolo2,3-bquinoxaline attached to the bulkier polyaromatic hydrocarbons such as fluoranthene, triphenylene, or polyphenylated benzene have been ...synthesized by a two-step procedure involving Sonogashira and Diels–Alder reactions. They were characterized by absorption, emission, electrochemical, thermal, and theoretical investigations. The electronic properties of the compounds were dominated by the 6H-indolo2,3-bquinoxaline chromophore, and the incorporation of polyaromatic hydrocarbons reduces the chances of nonradiative deactivation processes associated with the excited state and improves the emission properties. The compounds displayed cyan emission with moderate quantum efficiency when excited at the absorption maximum. All of the compounds exhibited an irreversible reduction process corresponding to the addition of electron at the quinoxaline segment. They showed moderate thermal stability and glass transition temperature greater than 100 °C. The presence of rigid 6H-indolo2,3-bquinoxaline and bulkier polyaromatic hydrocarbon segments enhances the thermal stability and glass transition temperature significantly. Finally, the dyes were successfully applied as an electron-transporting and emitting layer in multilayered organic light-emitting diodes comprising a N,N′-bis(l-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine hole-transporting layer. The cyan emitting devices were characterized by moderate device performance parameters.
Abstract
Concrete is the most preferable and widely used construction material in the infrastructure development. For concreting and curing huge amount of potable water is required and it is ...difficult to get this at all places and all times. One of the best alternative solution for this problem is using the self curing concrete. In this experimental study the mechanical properties of hardened concrete by partial replacement of cement by 0, 40 an 60% of GGBS for M20 and M35 grades of concrete using 0.5 and 1 percent of Poly ethylene glycol as self curing agent. Cubes and cylinders are cast and tested at age of 7 and 28 days, for compressive strength and split tensile strength. The results of conventional concrete are compared with the results of concrete with GGBS and Polyethylene glycol 400 for both grades of concrete. The test results have revealed that addition of 0.5% of self curing agent show higher strengths for 60% replacement of cement with GGBS while 1.0% of self curing agent showed good results for 40% replacement for M20 grade of concrete.
Organic dyes containing a triarylamine donor, a cyanoacrylic acid acceptor and a conjugation pathway composed of 2,7-carbazole, thiophene and fluorene have been synthesized and characterized as ...sensitizers for TiO 2 -based dye-sensitized solar cells. The effect of the nature of the conjugation bridge on the optical, electrochemical and photovoltaic properties has been investigated. Elongation of conjugation by the insertion of 2,7-carbazole or 2,7-fluorene π-linkers led to an increase in the molar extinction coefficients while the use of terthiophene red-shifted the absorption. Also the lengthening of the π-bridge helped to raise the lowest unoccupied molecular orbital of the dyes relative to the conduction band of TiO 2 . This increased the thermodynamic driving force for the electron injection from the excited dyes into the conduction band of TiO 2 . The trends in the optical properties of the dyes were also substantiated by TDDFT computations. DSSCs based on a dye containing terthiophene in the conjugation bridge exhibited the highest power conversion efficiency (4.9%) in the series attributable to its higher photocurrent ( J SC = 13.08 mA cm −2 ) generation. However, the dye with a fluorene linker exhibited high open circuit voltage ( V OC = 632 mV) and prolonged electron lifetime for the device. The role of the π-bridge in the charge transfer and electron recombination kinetics in the DSSC was elucidated by electrochemical impedance spectroscopic studies.
A new low‐band gap dyad DPP‐Ful, which consists of covalently linked dithiafulvalene‐functionalized diketopyrrolopyrrole as donor and fullerene (C60) as the acceptor, has been designed and ...synthesized. Organic solar cells were successfully constructed using the DPP‐Ful dyad as an active layer. This system has a record power‐conversion efficiency (PCE) of 2.2 %, which is the highest value when compared to reported single‐component organic solar cells.
Allein unterwegs: Die Kombination von Dithiafulvalen‐funktionalisiertem Diketopyrrolopyrrol (DPP) als Donor mit Fulleren (Ful) als Akzeptor erwies sich als nützlich. Die Dyade überzeugt mit einer außergewöhnlich hohen Effizienz bei der Stromumwandlung in organischen Einzelkomponenten‐Solarzellen (SC‐OSC). ITO=Indiumzinnoxid.
New organic dyes containing indolo2,3-bquinoxaline donor have been synthesized for application in dye sensitized solar cells as sensitizers. The dyes exhibited interesting optical properties tuneable ...by the nature of the conjugation bridge. Origin of the optical transitions in the dyes was corroborated by the TDDFT computations. The LUMO and HOMO of the dyes were found to be favourable for electron injection into the conduction band of TiO2 and the regeneration of the dye by the redox shuttle in the electrolyte, respectively. Since the dyes exhibited solvent dependent absorption properties, DSSC were fabricated from two different dye bath solutions, DCM and acetonitrile/tert-butanol/dimethylsulphoxide mixture. The dyes adsorbed from the later bath solution led to better device performance owing to the comparatively less charge transfer resistance arising from the well-spaced dye packing. Among all dyes, a dye containing thiophene in the π-spacer exhibited the highest device efficiency.
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A series of new organic dyes containing fluoreneamine-based donor and carbazole π-spacer are reported. These dyes displayed longer wavelength charge transfer absorption when compared to that of the ...corresponding phenylamine analogs. Fluoreneamine-based donors shifted the lowest unoccupied molecular orbital upwardly which is beneficial for the injection of electrons from the excited dye into the conduction band of TiO2 and lowered the oxidation potential of the dyes. The electronic perturbations caused by the fluorene unit have been confirmed by the density functional theoretical calculations. A device fabricated using a dye featuring difluorenylaminocarbazole donor and thiophene in the π-spacer exhibited promising power conversion efficiency (6.4%). The interfacial electron transfer kinetics has been elucidated by electrochemical impedance spectroscopy which showed the beneficial role of difluorenylamine unit in suppressing the electron recombination.
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•Organic dyes containing fluoreneamine donor and carbazole linker are reported.•The optical and photovoltaic properties are tuneable by fluorene substitution in donor.•A dye with difluorenylamine donor exhibited high power conversion efficiency (6.4%).•Difluorenylamine donor is beneficial to retard electron recombination.
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