wangzhaowei

A novel crosslinkable amino-functionalized conjugated polymer PFN-V is used as the cathode interlayer for high performance polymer solar cells, as reported by Lei Ying, Fei Huang, and co-workers in article number 1502563. The film can be rapidly crosslinked by UV-curing within 5 s in a nearly quantitative yield based on “thiol-ene” click reaction. This time- and labor-saving strategy may have practical applications in high throughput industrial production.

A new approach is presented to control the nanomorphology of organic solar cells in a predictable, controllable, and easily-scalable way. The nanoimprint lithography (NIL) is combined with a subsequent molecular diffusion step controlled by thermal annealing. The new approach is realized by using nanointerdigitated donor–acceptor structure, consisting of poly(3-hexylthiophene-2,5-diyl) nanopillar arrays surrounded by phenyl-C61-butyric acid methyl ester. Subsequent thermal annealing leads to vertically aligned ordered quasi-bulk heterojunctions with hierarchical nanostructure. The changes are studied in nanostructural and electrical properties of the pillar samples using scanning probe microscopy. In addition, grazing-incidence small and wide angle X-ray scattering yield detailed quantitative information on the molecular- to domain-scale nanostructures. The changes in crystal size, chain orientation, and domain composition as a function of thermal anneal temperature and time are obtained. In addition, the conductive scanning force microscopy in quantitative imaging mode, applied to the pillar-based samples for the first time, allows us to establish a clear relationship between nanomorphology, nanoelectrical property, and macroscale device performance. It is believed that the NIL combined with controlled molecular diffusion is a powerful method, which could be easily extended to other materials and processes to realize a whole variety of other hierarchical nanomorphologies.

With controlled mutual diffusion of donor and acceptor molecules on well-defined nanointerdigitated donor–acceptor pillar structure, quasi-bulk heterojunction pillars are formed in large area. The pillar nanostructures are effectively controlled by varying the thermal annealing conditions, showing nano- to macroscale structural and electrical properties easily monitored by grazing-incidence X-ray scattering, and scanning force microscopy.

For the first time, a new re-engineered polarized capacitor architecture for high energy density storage is demonstrated. Thin charge blocking layers are introduced at the electrode/dielectric interfaces. The insertion of these blocking layers leads to a likely reduction of charge injection into the dielectric material and a more than 200 V μm⁻¹ increase in the electric field breakdown of the dielectric.

Carrier dynamics in methylammonium lead halide (CH₃NH₃PbI_3–xCl_x) perovskite thin films, of differing crystal morphology, are examined as functions of temperature and excitation wavelength. At room temperature, long-lived (>nanosecond) transient absorption signals indicate negligible carrier trapping. However, in measurements of ultrafast photoluminescence excited at 400 nm, a heretofore unexplained, large amplitude (50%–60%), 45 ps decay process is observed. This feature persists for temperatures down to the orthorhombic phase transition. Varying pump photon energy reveals that the fast, band-edge photoluminescence (PL) decay only appears for excitation ≥2.38 eV (520 nm), with larger amplitudes for higher pump energies. Lower photon-energy excitation yields slow dynamics consistent with negligible carrier trapping. Further, sub-bandgap two-photon pumping yields identical PL dynamics as direct absorption, signifying sensitivity to the total deposited energy and insensitivity to interfacial effects. Together with first principles electronic structure and ab initio molecular dynamics calculations, the results suggest the fast PL decay stems from excitation of high energy phonon modes associated with the organic sub-lattice that temporarily enhance wavefunction overlap within the inorganic component owing to atomic displacement, thereby transiently changing the PL radiative rate during thermalization. Hence, the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies.

Ultrafast photoluminescence dynamics in CH₃NH₃PbI_3–xCl_x perovskite thin films are examined as functions of pump wavelength, temperature, and film morphology. A previously unexplained, rapid decay feature in emission, which occurs only for above-gap excitation and lacks thermal activation, arises from organic-to-inorganic thermalization of phonons. Density functional theory and transient mid-infrared spectroscopy further support the assignment of this important dissipation mechanism.