The authors show that a photovoltaic device composed of a -donor-bridge–acceptor-bridge- type block copolymer thin film exhibits a significant performance improvement over its corresponding donor/acceptor blend (Voc increased from 0.14to1.10V and Jsc increased from 0.017 to 0.058mA∕cm2) under identical conditions, where donor is an alkyl derivatized poly-p-phenylenevinylene (PPV) conjugated block, acceptor is a sulfone-alkyl derivatized PPV conjugated block, and bridge is a nonconjugated and flexible unit. The authors attribute such improvement to the block copolymer intrinsic nanophase separation and molecular self-assembly that results in the reduction of the exciton and carrier losses.
We report residual resistivity ratio (RRR) values (up to RRR-541) measured in thin film
Nb grown on MgO crystal substrates, using a vacuum arc discharge, whose 60–160 eV
Nb ions drive heteroepitaxial crystal growth. The RRR depends strongly upon
substrate annealing and deposition temperatures. X-ray diffraction spectra and
pole figures reveal that, as the crystal structure of the Nb film becomes more
ordered, RRR increases, consistent with fewer defects or impurities in the lattice
and hence longer electron mean free path. A transition from Nb(110) to purely
Nb(100) crystal orientation on the MgO(100) lattice occurs at higher temperature.
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