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.
Multicrystalline silicon wafer solar cells reveal performance‐ reducing defects by luminescence. X‐ray fluorescence spectra are used to investigate the elemental constituents from regions of solar cells yielding reverse‐bias or sub‐bandgap luminescence from defects. It is found that a higher concentration of metals is present in regions yielding reverse‐bias electroluminescence than in regions yielding sub‐bandgap electroluminescence. This suggests, dislocations do not create strong breakdown currents in the absence of impurity precipitates.
The growth, structural and optical characterisation of dilute nitride alloys of InSb grown by plasma‐assisted molecular beam epitaxy is presented. The layers were characterised by high‐resolution X‐ray diffraction indicating high crystalline quality and nitrogen incorporations up to 0.68%. Fourier‐transform infrared absorption measurements reveal the position of the absorption edge to be a result of the competing effects of bandgap reduction (due to nitrogen incorporation and bandgap renormalisation) and Moss–Burstein band filling.
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 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.
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.
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.
The authors describe an organic complementary inverter with N,N′‐ditridecyl‐3,4,9,10‐perylenetetracarboxylic diimide as an n‐type semiconductor and pentacene as a p‐type semiconductor. Each transistor of the inverter exhibited high carrier mobility: 1.62 cm2/Vs for an n‐type drive transistor and 0.57 cm2/Vs for a p‐type switch transistor. The gain of the inverter reached 125. Another inverter using Ta2O5 as a high κ gate dielectric performed well with a gain of 500 and an operation voltage of only 5 V.
We report the fabrication procedure and the characterization of an Al0.3Ga0.7As solar cell containing high‐density GaAs strain‐free quantum dots grown by droplet epitaxy. The production of photocurrent when two sub‐bandgap energy photons are absorbed simultaneously is demonstrated. The high quality of the quantum dot/barrier pair, allowed by the high quality of nanostructured strain‐free materials, opens new opportunities for quantum dot based solar cells.
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.
Here, we demonstrate the synthesis of graphene on Ag foil by an atmospheric‐pressure (AP) chemical vapor deposition (CVD) process as tarnish‐resistant coating. Synthesis of a continuous graphene film on Ag foil is achieved using the solid camphor as carbon precursor in a gas mixture of Ar and H2. Tarnishing of the Ag surface through sulfidation is investigated with and without coating of the graphene film. It is observed that the bare Ag surface immediately reacts with sulfur vapor to turn black, whereas graphene coating passivates the Ag surface robustly and thereby restrains the sulfur reaction to preserve from tarnishing. Our findings show that a large‐area graphene film can be effectively grown on Ag surface by a CVD process as a tarnish and corrosion resistance barrier.
We demonstrate the monolithic integration of a microstructured organic photodiode with a planar optical stripe waveguide. The manufacturing of this waveguide‐integrated organic photodiode is based on an UV photolithography process. The integration of photodiodes with optical waveguides represents an essential building block in the field of optoelectronic‐photonic integrated circuits.
A high‐stability Eu complex has been achieved by coating with a silica glass via a low temperature sol–gel process using deuterated methanol. A three‐dimensional glass network protects the Eu complex from free oxygen and/or water to change the ligand structure. In addition, the chemical bond of the deuterated Eu complex is more stable than that of the conventional Eu complex. Therefore, we achieved a high‐thermal‐stability Eu complex encapsulated by a sol–gel derived silica glass using deuterated methanol instead of ethanol.
Bi2Te3 doped p‐type Pb0.13Ge0.87Te samples were prepared by hot pressing. We report on very high power factor values of ～30 μW/cm K2 at 500 °C, as were determined from Seebeck coefficient and electrical resistivity measurements. From dilatometric characterization, the phase transition from the low temperature rhombohedral to the high temperature cubic NaCl structures, takes place at 373 °C. This transition is accompanied by a continuous and gradual change of the lattice parameters, as was observed by hot stage XRD, suggesting a good mechanical durability upon thermal cycling and operating in large thermal gradients.
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.
An original approach is proposed to study the magnetic phase separation phenomenon. It is based on the registration of the noise‐like FMR Fine Structure (FMR FS) caused by the magnetic interparticle dipole–dipole interaction between spatially separated ferromagnetic regions. Data obtained for a La0.7Pb0.3MnO3 single crystal point to the existence of spatially separated ferromagnetic regions. It is shown that FMR FS of the La0.7Pb0.3MnO3 single crystal is temperature reversible and disappears at the maximum of magnetoresistance.
The rising interest in low temperature heat energy conversion encourages the application of thermoelectric devices. However, conventional thermoelectric devices used in the Seebeck mode as thermoelectric generators have several shortcomings and thus are inefficient when used as a generator. Additionally, the high cost–power ratio of these modules anticipates the commercial success on a broad basis. One way to achieve better suited products is provided by miniaturization of thermoelectric devices in order to enable the use of mass production methods. But in small devices the contact effects become dominant and reduce the efficiency and power density considerably. We show that using pn‐junctions with thermal generation of free carriers offers the possibility to achieve better contact properties and thus higher efficiencies and power densities.
We demonstrated important changes produced on the modulation frequency of hybrid organic–inorganic light‐emitting diodes to examine the applicability as a light source for visible optical communications. The fabricated device structure was 4,4′‐bis[N ‐(1‐napthyl)‐N ‐phenyl‐amino]biphenyl/4,4′‐(bis(9‐ethyl‐3‐carbazovinylene)‐1,1′‐biphenyl:4,4′‐bis[9‐dicarbazolyl]‐2,2′‐biphenyl/ZnS/LiF/MgAg. This device showed an improvement in the modulation frequency using ZnS instead of an organic material, tris(8‐hydroxyquinoline)aluminum. A maximum cutoff frequency of 20.6 MHz was achieved.
