We propose a theory of thin film photovoltaics in which one of the polycrystalline films is made of a pyroelectric material grains such as CdS. That film is shown to generate strong polarization improving the device open circuit voltage. Implications and supporting facts for the major photovoltaic types based on CdTe and CuIn(Ga)Se2 absorber layers are discussed.
In this Letter we demonstrate that hydrogen‐terminated porous silicon (PSi) layers and powders can serve as highly efficient reductive templates for noble metal salts. The reduction results in metal nanoparticle (NP) formation in the pores of PSi. Gold NP formation has been monitored in‐situ by measuring the plasmon resonance response. Pt NPs, formed in the PSi matrix, were investigated by transmission electron microscopy and energy‐dispersive X‐ray analysis. Furthermore, hybrid Pt/PSi nanocomposites exhibit a high catalytic activity for CO oxidation.
We report on wet etching of photomodified regions in crystalline sapphire using KOH solution. Tightly focused femtosecond laser pulses (150 fs at 800 nm wavelength) were used to create void structures enclosed in an amorphised sapphire shell inside the bulk of a crystalline host. The diameter of the amorphous regions can be controlled by pulse energy and was typically 0.5–1.5 µm. The etching rate depends on the distance between adjacent irradiation spots, pulse energy, concentration of etchant and ultrasonic agitation.
We report on solution‐processible polymer solar cells (PSCs) fabricated on a papery substrate using carton. Highly conductive PEDOT:PSS was used as a bottom anode and planarization layer, and a semi‐transparent top cathode was applied. This research could be an important approach to the development of all‐solution‐processible papery PSCs as well as paper electronics.
Metallic single‐walled carbon nanotubes (m‐SWCNTs) with excellent conductivity and transparency are considered to be eminent electrode materials. However, it still remains a challenge to separate m‐SWCNTs by their diameters. As reported in this Letter, by effective purification treatment of SWCNTs, we succeeded in achieving diameter separation of m‐SWCNTs using gel column chromatography. TEM and Raman characterizations revealed that metal catalysts and amorphous carbon on tube surfaces were largely reduced, which contributed to the diameter separation of m‐SWCNTs.
Epitaxial TiC/SiC multilayers were grown by magnetron sputtering at a substrate temperature of 550 °C, where SiC is normally amorphous. The epitaxial TiC template induced growth of cubic SiC up to a thickness of ～2 nm. Thicker SiC layers result in a direct transition to growth of the metastable amorphous SiC followed by renucleation of nanocrystalline TiC layers.
A passive micro‐displacement sensor (for ～μm displacement) was fabricated based on a magnetoelectric laminate, in which the displacement change can result in a change of the magnetic flux around the magnetoelectric sensor. The displacement measurement was realized by measuring the magnetoelectric output voltage. The displacement detecting coefficient was ～2.5 mV/μm at a frequency of ～1 kHz. This passive displacement sensor possesses the advantages of low cost, high resolution, low energy consumption and good linearity and has potential for application in future displacement detectors.
Heteroepitaxial growth of kesterite Cu2ZnSnS4 (CZTS) thin film on cubic ZnS(100) single crystal substrate was achieved by radio frequency magnetron sputtering from a single CZTS target. An optimal substrate temperature in the range of 470–500 °C is found suitable for this epitaxial growth. The growth of CZTS was confirmed to be along a‐axis. The sputtered CZTS thin film is homogeneous throughout the whole film. The band gap of the film is found to be approximately 1.51 eV, i.e., promising for high efficiency thin film solar cells.
Optically transparent and high‐quality hybrid ZnO nanoparticle and anthracene embedded polyphenylsiloxane (PPS) glass films were spin‐coated on quartz substrates. A strong Förster resonant energy transfer (FRET) process was indicated by the observation of quenching of the ZnO emission and an enhancement of the anthracene emission at room temperature. The efficiency of this energy transfer between ZnO and the S1 vibronic states of the anthracene molecules can be optimized to exceed 90%.
A facile metal catalyst free route to synthesize boron doped (0.6%–1.0%) carbon nanotubes via ceramic nanowires in which the formation of the nanowires (probably serving as templates), the carbon nanotubes and their doping all occur unanimously in the reaction, is presented.
This Letter reports on the assembly on the tip of an optical fibre of a metamaterial film fabricated by a self‐assembly bottom‐up method, composed of silver nanowires embedded in an alumina matrix. By illuminating the film through the fibre in a reflection configuration, we observe experimentally the optical response of the metamaterial in agreement with theoretical predictions and interpreted as the excitation of surface plasmon‐polaritons in the cylindrical surface of the nanowires. These results pave the way for low‐cost optical fibre devices that incorporate metamaterial films.
Osmium diboride has been known for some time as a low compressibility material and a superhard material. It is suitable for hard coating applications. It is also a superconductor below 2.1 K. Using first‐principles calculations, the author investigated the geometry of its Fermi surface (FS) and calculated the related physical quantities. The theoretical results are used to predict the frequencies of the Shubnikov–de Haas quantum oscillations. Comparison with recent measurements of the magneto‐resistance oscillations in osmium diboride is made.
The Fe3O4(111)/graphene/Ni(111) trilayer is proposed to be used as an ideal spin‐filtering sandwich where the half‐metallic properties of magnetite are used. Thin magnetite layers on graphene/Ni(111) were prepared via successive oxidation of a thin iron layer predeposited on graphene/Ni(111) and the formed system was investigated by means of low‐energy electron diffraction and photoelectron spectroscopy. The electronic structure and structural quality of the graphene film sandwiched between two ferromagnetic layers remain unchanged upon magnetite formation as confirmed by experimental data.
Ultrafast transverse thermoelectric voltage response has been observed in c‐axis inclined epitaxial La0.5Sr0.5CoO3thin films. Voltage signals with the rise time of 7 ns have been detected under the irradiation of pulse laser with duration of 28 ns. A concept, named response rate ratio, has been proposed to evaluate the intrinsic response rate, and this ratio in La0.5Sr0.5CoO3is smaller than that in other reported materials. The low resistivity is thought to be responsible for the ultrafast response, as low resistivity induces small optical penetration depth, and response time has a monotonous increasing relationship with this depth.
We report on the photoconductance in two‐dimensional arrays of gold nanorods. The arrays are formed by a combination of droplet deposition and stamping methods. We find that the plasmon induced photoconductance is sensitive to the linear polarization of the exciting photons consistent with the excitation of the longitudinal surface plasmon resonance of the nanorods.
Steady‐state and time‐resolved photoluminescence of silicon nanoparticles dispersed in low‐polar liquids at above room temperature is studied. The roles of low‐polar liquids as well as mechanisms responsible for their temperature‐dependent photoluminescence are discussed. The thermal sensitivity of the photoluminescence is estimated and application of the nanoparticles as nanothermometers is proposed.
We have shown that nitrophenyl groups may be added to the surface of few‐layer epitaxial graphene (EG) by the formation of covalent carbon–carbon bonds thereby changing the electronic structure and transport properties of EG from near‐metallic to semiconducting. In the present Letter we discuss the opportunities afforded by such chemical processes to engineer device functionality in graphene by modification of the electronic properties without physical patterning.
