Charge carrier mobilities in conjugated semicrystalline polymers depend on morphological parameters such as crystallinity, crystal orientation, and connectivity between ordered regions. Despite recent progress in the development of conducting polymers, the complex interplay between the aforementioned parameters and their impact on charge transport is not fully understood. By varying the casting solvents and thermal annealing, we have systematically modulated the crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[2,5-bis(3-hexadecylthiophen-2yl)thieno(3,2-b)thiophene] (PBTTT) thin films to examine the role of microstructure on charge mobilities. In particular, we achieve equal crystallinities through different processing routes to examine the role of structural parameters beyond the crystallinity on charge mobilities. As expected, a universal relationship does not exist between the crystallinity in either P3HT and PBTTT active layers and the charge mobility in devices. In P3HT films, higher boiling point solvents yield longer conjugation lengths, an indicator of stronger intracrystalline order, and therefore higher device mobilities. In contrast, the charge mobilities of PBTTT devices depend on the interconnectivity between crystallites and intercrystalline order in the active layer.

Ceramic anodes comprising infiltrated SrMoO 4 in porous ytttria-stabilized zirconia were investigated. Upon reduction at 1073 K, the electronically insulating SrMoO 4 phase transformed to SrMoO 3 , which has a bulk electronic conductivity of 10 3 S cm −1 under fuel cell conditions. An anode conductivity of 20 S cm −1 was achieved with a low SrMoO 4 loading of 13 vol % of the total anode. The infiltrated composite is dimensionally stable upon redox cycling, and a Pd catalyst was required to achieve good fuel cell performance. Fuel cell performance with methane was lower than with hydrogen. This lower methane performance could be due to coking.Solid oxide fuel cells ͑SOFCs͒ are a promising fuel flexible technology for clean and efficient conversion of chemical energy to electrical energy. While the fuel flexibility of SOFCs is widely considered a key benefit, it is well known that the conventional nickelyttria-stabilized zirconia ͑Ni-YSZ͒ cermet anode catalyzes the formation of deleterious carbon filaments in the presence of hydrocarbons. 1 This carbon fiber formation results in deactivation of the Ni surface, loss of Ni by metal dusting, 2 and anode fracture induced by carbon fiber growth. 3 Other drawbacks of Ni include catalytic poisoning in the presence of sulfur and low redox stability. 4,5 Replacement of Ni with an electronic conducting ceramic has generated great interest because ceramics tend to be more fuel flexible and sulfur tolerant than Ni. The target anode must offer ionic/ electronic conductivity, gas transport, and catalytic activity for fuel oxidation. Of these requirements, Ni provides both electronic conductivity and catalytic activity for the oxidation reaction. With a single metal oxide material, it is difficult to achieve high electronic conductivity and catalytic activity. Implementation of a single metal oxide to fulfill both roles would be simpler; however, incorporating two separate materials allows for independent optimization of an electronic conductor and oxidation catalyst. 6 In this paper, we focus on the development of a highly conductive ceramic anode into which any catalyst of choice can be incorporated.The target electronic conductivity for anode materials has been outlined in a review by Atkinson et al. 7 These authors have argued that the required anode conductivity under operating conditions can be relaxed to as low as 1 S cm −1 depending on cell design. The highest performing anodes are typically porous composites of the electrolyte ͑YSZ͒ and an electronic conductor. The composite conductivity of the electrode is strongly dependent on the structure. For example, the conductivity of a conventional Ni-YSZ composite is 10 3 S cm −1 , even though Ni has a conductivity of 10 6 S cm −1 . 8 Compared to conventional cosintering methods, composites formed by infiltration have the advantage of providing higher conductivity at lower volume percent ͑vol. %͒ loadings of the electronic conductor. 9 However, even with infiltrated composites, the conductivity of the composite will be at leas...

A comprehensive experimental study was conducted on the dealloying of PdNi6 nanoparticles under various conditions. A two-stage dealloying protocol was developed to leach >95% of Ni while minimizing the dissolution of Pd. The final structure of the dealloyed particle was strongly dependent on the acid used and temperature. When H2SO4 and HNO3 solutions were used in the first stage of dealloying, solid and porous particles were generated, respectively. The porous particles have a 3-fold higher electrochemical surface area per Pd mass than the solid ones. The dealloyed PdNi6 nanoparticles were then used as a core material for the synthesis of core-shell catalysts. These catalysts were synthesized in gram-size batches and involved Pt displacement of an underpotentially deposited (UPD) Cu monolayer. The resulting materials were characterized by scanning transmission electron microscopy (STEM) and in situ X-ray diffraction (XRD). The oxygen reduction reaction (ORR) activity of the core-shell catalysts is 7-fold higher than the state-of-the-art Pt/C. The high activity was confirmed by a more than 40 mV improvement in fuel cell performance with a Pt loading of 0.1 mg cm(-2) by using the core-shell catalysts.

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Microphase-separated block copolymers composed of electron donor and acceptor blocks may provide morphology control to address many challenges in organic electronics. Crucial to controlling the self-assembly of fully conjugated block copolymers is tuning the interplay between crystallization of the individual blocks and microphase separation between the donor and the acceptor. Thus, we have examined the kinetics of the morphological evolution in P3HT-b-PFTBT block copolymer films during two processes: solution casting and thermal annealing. We use in situ wide-angle and small-angle grazing incidence X-ray scattering to monitor the crystallization of P3HT and microphase separation between the two blocks. We find that during film drying, initial P3HT crystallization happens quickly, before phase separation of the two blocks. However, crystallization is significantly suppressed with respect to neat materials, enabling microphase separation to proceed at time scales after some initial crystallization of the donor block takes place. This enables a mesoscale structure to develop during processes such as thermal annealing because self-assembly of the lamellar structure takes place before the crystallization of the donor block is complete. We also find that significant crystallization of PFTBT blocks after P3HT crystallization is possible at elevated temperatures. Crystallization of both blocks is important to maximize the performance of solar cells and transistors with block copolymer active layers. As a consequence, we exceed 3% average power conversion efficiencies in P3HT-b-PFTBT photovoltaic devices.