We report on the fabrication of heterojunction solar cells made by deposition of transparent conducting oxide (TCO) films on Cu2O substrates. The TCO films have been grown by ion beam sputtering on good quality Cu2O sheets prepared by oxidizing copper at a high temperature. The best solar cell has reached an open-circuit voltage of 0.595V, a short-circuit current density of 6.78mA∕cm2, a fill factor of 50%, and a conversion efficiency of 2% under simulated AM1.5G illumination, which is the highest efficiency value reported for this kind of heterojunction devices. These devices represent a good starting point for the development of very low cost solar cells.

Novel polymer-based piezoelectric nanocomposites with enhanced electromechanical properties open new opportunities for the development of wearable energy harvesters and sensors. This paper investigates how the dissolution of different types of hexahydrate metal salts affects β-phase content and piezoelectric response (d33) at nano- and macroscales of polyvinylidene fluoride (PVDF) nanocomposite films. The strongest enhancement of the piezoresponse is observed in PVDF nanocomposites processed with Mg(NO3)2⋅6H2O. The increased piezoresponse is attributed to the synergistic effect of the dipole moment associated with the nucleation of the electroactive phase and with the electrostatic interaction between the CF2 group of PVDF and the dissolved salt through hydrogen bonding. The combination of nanofillers like graphene nanoplatelets or zinc oxide nanorods with the hexahydrate salt dissolution in PVDF results in a dramatic reduction of d33, because the nanofiller assumes a competitive role with respect to H-bond formation between PVDF and the dissolved metal salt. The measured peak value of d33 reaches the local value of 13.49 pm/V, with an average of 8.88 pm/V over an area of 1 cm2. The proposed selection of metal salt enables low-cost production of piezoelectric PVDF nanocomposite films, without electrical poling or mechanical stretching, offering new opportunities for the development of devices for energy harvesting and wearable sensors.

SummaryGraphene films were produced by chemical vapor deposition (CVD) of pyridine on copper substrates. Pyridine-CVD is expected to lead to doped graphene by the insertion of nitrogen atoms in the growing sp2 carbon lattice, possibly improving the properties of graphene as a transparent conductive film. We here report on the influence that the CVD parameters (i.e., temperature and gas flow) have on the morphology, transmittance, and electrical conductivity of the graphene films grown with pyridine. A temperature range between 930 and 1070 °C was explored and the results were compared to those of pristine graphene grown by ethanol-CVD under the same process conditions. The films were characterized by atomic force microscopy, Raman and X-ray photoemission spectroscopy. The optical transmittance and electrical conductivity of the films were measured to evaluate their performance as transparent conductive electrodes. Graphene films grown by pyridine reached an electrical conductivity of 14.3 × 105 S/m. Such a high conductivity seems to be associated with the electronic doping induced by substitutional nitrogen atoms. In particular, at 930 °C the nitrogen/carbon ratio of pyridine-grown graphene reaches 3%, and its electrical conductivity is 40% higher than that of pristine graphene grown from ethanol-CVD.

The optical limiting properties of a one-dimensional, transparent metallodielectric photonic band\ud gap structure are studied. Due to light confinement in the structure that enhances the nonlinear\ud response of the layers, a nonlinear transmission dependence on the incident light intensity is found.\ud Experimental results are reported for a four period sample where the single period consists of ZnO\ud and Ag layers 109 and 17 nm thick, respectively. The structure was designed to exhibit a\ud transmission resonance at 532 nm. Under the action of a Q-switched frequency doubled\ud Nd:yttrium–aluminum–garnet laser, a decrease in transmission of approximately 50% is obtained\ud for a maximum incident light intensity of 2 GW/cm2. These results are explained in terms of a\ud dynamic change of the absorption coefficient due to the enhancement of the two-photon absorption\ud process. These results suggest that the structure is suitable for optical limiting applications in the\ud visible range

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