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A new dyad of fullerene/disperse-red, denoted as PCBDR, strongly absorbs visible light in the range of 400–600 nm. PCBDR showed advantages over PCBM in several aspects such as enhanced visible-light absorption, improved solubility, and the possibility to facilitate cascaded electron transfer. P3HT:PCBDR bulk heterojunction (BHJ) solar cells, nevertheless, so far have not outperformed P3HT:PCBM BHJ solar cells under similar conditions. Among factors that affect the efficiency of P3HT:PCBDR BHJ solar cells, the suppression of the interchain interaction of P3HT in the P3HT:PCBDR blend played a major role, presumably due to better interfacial miscibility between P3HT and PCBDR than that in blends of P3HT:PCBM. In contrast, benzoporphyrin (BP), due to its unique crystallinity, morphology, and nonsolubility, afforded a better control of the morphology and the interface of the p/n junctions. As a consequence, the performance of solar cells with BP/PCBDR as the active layer was comparable to that of BP/PCBM solar...

The evaluation of the power conversion efficiency (PCE) of new materials for organic bulk heterojunction (BHJ) photovoltaics is difficult due to the large number of processing parameters possible. An efficient procedure to determine the optimum conditions for thermal treatment of polymer-based bulk heterojunction photovoltaic devices using in situ current-voltage measurements is presented. The performance of a new fullerene derivative, 1,9-dihydro-64,65-dihexyloxy-1,9-(methano[1,2] benzomethano)fullerene[60], in BHJ photovolatics with poly(3-hexylthiophene) (P3HT) was evaluated using this methodology. The device characteristics of BHJs obtained from the in situ method were found to be in good agreement with those from BHJs annealed using a conventional process. This fullerene has similar performance to 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methano fullerene in BHJs with P3HT after thermal annealing. For devices with thickness of 70 nm, the short circuit current was 6.24 mA/cm2 with a fill factor of 0.53 and open circuit voltage of 0.65 V. The changes in the current-voltage measurements during thermal annealing suggest that the ordering process in P3HT dominates the improvement in power conversion efficiency. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

A straightforward, "one-pot" approach to the construction of a new class of molecular tweezers and their heterogenization onto various aminated materials is reviewed here. It is based on nucleophilic substitution of the cyanuric chloride scaffold with tailored aminoporphyrin subunits. The molecular recognition properties of these porphyrinic materials for diamine sensing are also discussed.

A new method for synthesizing gold, nickel, and cobalt metal nanoparticles at room temperature from metal salts employing plasmid DNA in a toroidal topology as a sacrificial mold is presented. The diameter of the toroidal DNA drives the formation and size of the nanoparticle, and UV light initiates the oxidation of the DNA and concomitant reduction of the DNA bound metal ions. The nanoparticles were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and electron diffraction (ED).

Stepwise amination of cyanuric chloride (1) with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (2) and/or its zinc(II) complex (3) enables the synthesis of porphyrin-porphyrin dyads with predetermined free base-free base forms or free base-zinc and zinc-zinc metalation states. Furthermore, the use of aminopropyl-silanized silica gel as a scavenger for unwanted byproducts allowed the one-pot synthesis of title porphyrin compounds in high yield and purity with minimum use of preparative column chromatography.

A core phthalocyanine platform allows engineering of the solubility properties the band gap, shifting the maximum absorption toward the red. A simple method for increasing the efficiency of heterojunction solar cells uses a self-organized blend of phthalocyanine chromophores fabricated by solution processing.

The improvement of the power conversion efficiency (PCE) of polymer bulk heterojunction (BHJ) solar cells has generally been achieved through synthetic design to control frontier molecular orbital energies and molecular ordering of the electron-donating polymer. An alternate approach to control the PCE of a BHJ is to tune the miscibility of the fullerene and a semiconducting polymer by varying the structure of the fullerene. The miscibility of a series of 1,4-fullerene adducts in the semiconducting polymer, poly(3-hexylselenophene), P3HS, was measured by dynamic secondary ion mass spectrometry using a model bilayer structure. The microstructure of the bilayer was investigated using high-angle annular dark-field scanning transmission microscopy and linked to the polymer-fullerene miscibility. Finally, P3HS:fullerene BHJ solar cells were fabricated from each fullerene derivative, enabling the correlation of the active layer microstructure to the charge collection efficiency and resulting PCE of each system. The volume fraction of polymer-rich, fullerene-rich, and polymer-fullerene mixed domains can be tuned using the miscibility leading to improvement in the charge collection efficiency and PCE in P3HS:fullerene BHJ solar cells. These results suggest a rational approach to the design of fullerenes for improved BHJ solar cells.

A straightforward, "one-pot" approach to the construction of a new class of molecular tweezers and their heterogenization onto various aminated materials is reviewed here. It is based on nucleophilic substitution of the cyanuric chloride scaffold with tailored aminoporphyrin subunits. The molecular recognition properties of these porphyrinic materials for diamine sensing are also discussed.

We have designed the synthesis of “deconvoluted fullerene” derivatives that present an ordered pattern of hexagons and pentagons in the backbone of the molecule. We not only mimicked the fullerene structure in dihedral planes, but also preserved its electron accepting behavior and enlarged its optical absorption. Moreover, very preliminary photoluminescence (PL) quenching experiments also confirmed the potentiality of these materials as acceptors in the field of organic photovoltaics (OPV)s. A brief discussion of the surface morphology, based on AFM analysis, is also presented.

Light and flexible photovoltaic devices based on organic materials are extensively studied as an alternative to expensive and fragile silicon-based solar cells. The efficiency of these devices is rapidly increasing with the most recent power conversion efficiency (PCE) of greater than 8% bringing them closer to commercial viability. Further improvements are needed and can be achieved by optimizing the ratio between donor and acceptor, modifying the electronic properties of the materials, and optimizing the morphology of the resulting bulk heterojunction (BHJ). A direct way to increase the efficiency is to lower the band gap of the donor material in order to absorb a greater fraction of the solar spectrum. This concept has been explored through the synthesis of a series of new low band gap polymers, which exhibit a decreased band gap as a result of lowering the lowest unoccupied molecular orbital (LUMO). An emerging challenge is the need for electronically compatible acceptors with sufficiently low LUMO levels so that charge separation is efficiently promoted. Optimum miscibility of a specific polymer and fullerene combination to create the optimum degree of phase separation is also a feature to take into account. Typically, the approach used to test new donor materials is to fabricate devices using PC61BM ([6,6]-phenyl-C61-butyric acid methyl ester), a well-studied benchmark acceptor. Only a limited number of other fullerene derivatives have been successfully employed. Although these fullerene derivatives bear different functional groups, they are related by the positioning of the substituents on carbons 1 and 2 of a six-membered ring. From literature studies it is apparent that even subtle modification of the nature and especially position of substituents can drastically alter the electronic properties of fullerene derivatives. For example, PC71BM has reduced symmetry that increases visible light absorption and has a positive effect on current generation in polymer BHJ cells. Here we report the synthesis of a series of novel fullerene derivatives functionalized through the “1,4” position and their use in organic photovoltaics (OPVs). Features that distinguish this class of fullerene derivatives are: 1) straightforward synthesis which includes versatility of functionalization with different substrates starting from the same material (fullerenol, Scheme 1); 2) tunable LUMO energy by appending electron-donating or electron-withdrawing groups; 3) lower symmetry which decreases the optical gap and produces an increased absorption in the visible (the extinction coefficient at 480 nm of a 1,4-adduct is approximately 8 times larger than that of PCBM) ; 4) tunable solubility which influences the morphology of the BHJ. Like PC71BM, 1,4addends have increased light absorption at ca. 500 nm (Figure 1) with the advantage that all the C60 derivatives

The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices.

The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices.

Dimeric metalloporphyrin hosts with tweezer-like structures have been synthesized by reacting the cyanuric chloride scaffold, CC, with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, P, and 5-(4-aminophenyl)-10,15,20-trimesitylporphyrin, M, to yield the homoconjugates free bases PP and MM and the heterodyad PM. Metalation with Zn(II), gives three structurally related ditopic receptors P(Zn)P(Zn), P(Zn)M(Zn), and M(Zn)M(Zn) with differential steric hindrance and conformational rigidity. The solution structure and supramolecular properties of these porphyrin dimers have been investigated as isolated molecules and in the presence of aliphatic alpha,omega-diamines of general formula H(2)N-(CH(2))(n)-NH(2) (n = 4-8) by spectroscopic and theoretical studies including multidimensional NMR, UV-vis, molecular modeling, and computational NMR methods. Binding constants in the range 4.2 x 10(6) to 3.4 x 10(7) M(-1) are observed in dichloromethane at 298 K, with a 3 orders of magnitude increase as compared to monodentate nBuNH(2), thus indicating the occurrence of a host-guest ditopic interaction. Linear correlation graphs are obtained by plotting the Soret band shift (Delta nu, cm(-1)) of the complex as a function of the diamine chain length. Combined NMR evidence and OPLS 2005 Force Field conformational analysis point to a mutual adaptation of both the binding partners in the host-guest complex, whose geometry is mainly dictated by the steric impact of the bulky substituents at the porphyrin periphery.

The highly fluorinated alkyl moieties of a new porphyrin drive the self-organization of thin films with C(60) on ITO electrodes.

Clicking thiols onto a core fluorous phthalocyanine (Pc) platform yields alkyl and fluoroalkyl derivatives. The Zn(II) Pc with 16 thioalkanes self-organizes with fullerene C60 into nearly monodispersed nanoparticles when cast on ITO surfaces. Particle size and surface density is controlled by varying the Pc/fullerene ratio and concentration. Fluorescence quenching indicates electronic interaction between the component molecules in the films of nanoparticles. The strong supramolecular interactions between the Pc with 8 or 16 fluorous alkanes inhibit incorporation of the fullerene.

Multifunctional molecules bearing different dyes, such as donor–acceptor systems, synthesized by covalent chemistry have provided a wealth of information on the fundamental nature of electron and energy transfer in organic systems and there is a growing literature on the materials properties of dyes on surfaces. However, in the vast majority of cases the synthetic costs of producing these covalently bound systems prohibit them from deployment in commercially viable devices. Thus, to achieve both the needed multifunctionality and to bring the synthetic costs in line with potential commercialization, supramolecular approaches to the formation of photonic materials can be exploited. This perspective focuses on porphyrinoids as exemplary dyes, but the concepts and design principles extend to other chromophores.