Polyvinylidene Fluoride (PVDF) piezoelectric electrospun nanofibers have been intensively used for sensing and actuation applications in the last decade. However, in most cases, random PVDF piezoelectric nanofiber mats have moderate piezoelectric response compared to aligned PVDF nanofibers. In this work, we demonstrate the effect of alignment conducted by a collector setup composed of two-metal bars with gab inside where the aligned fiber can be formed. That is what we called static aligned nanofibers, which is distinct from the dynamic traditional technique using a high speed rotating drum. The two-bar system shows a superior alignment degree for the PVDF nanofibers. Also, the effect of added carbon nanotubes (CNTs) of different concentrations to PVDF nanofibers is studied to observe the enhancement of piezoelectric response of PVDF nanofibers. Improvement of β-phase content of aligned (PVDF) nanofibers, as compared to randomly orientated fibers, is achieved. Significant change in the piezoelectricity of PVDF fiber is produced with added CNTs with saturation response in the case of 0.3 wt % doping of CNTs, and piezoelectric sensitivity of 73.8 mV/g with applied masses down to 100 g.

This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria nanoparticles reduce Ce⁴⁺ to Ce³⁺ which follow the rule of improving conductivity of solar cells through the hopping mechanism. The existence of Ce³⁺ helps in the down-conversion from 430 nm excitation to 530 nm emission. The erbium dopant forms energy levels inside the low-phonon ceria host to up-convert the 780 nm excitations into green and red emissions. When coating reduced erbium-doped ceria nanoparticles on the back side of a solar cell, a promising improvement in the solar cell efficiency has been observed from 15% to 16.5% due to the mutual impact of improved electric conductivity and multi-optical conversions. Finally, the impact of the added coater on the electric field distribution inside the solar cell has been studied.

A series of novolac phenolic polymeric networks (NPPN) were prepared via an acid-catalyzed polycondensation reaction of formaldehyde with chalcones possessing a p-phenolic OH group. When p-hydroxybenzaldehyde was treated with formaldehyde under the same conditions, a phenolic polymer (PP) was obtained. The resulting polymers were isolated in excellent yields (83–98%). Isolated polymers (NPPN, PP) were characterized using FTIR, TGA, and XRD. The results obtained from the TGA revealed that all prepared phenolic polymers have high thermal stability at high temperatures and can act as thermosetting materials. XRD data analysis showed a high degree of amorphousness for all polymers (78.8–89.2%). The electrical conductivities and resistivities of all chalcone-based phenolic networks (NPPN) and p-hydroxybenzaldehyde polymer (PP) were also determined. The physical characteristics obtained from the I-V curve showed that the conductivity of phenolic polymers has a wide range from ultimately negligible values of 0.09 µS/cm up to 2.97 μS/cm. The degree of polarization of the conjugated system’s carbonyl group was attributed to high, low, or even no conductivity for all phenolic polymers since the electronic effects (inductive and mesomeric) could impact the polarization of the carbonyl group and, consequently, change the degree of the charge separation to show varied conductivity values.

This paper introduces electrospun nanofibers embedded with ceria nanoparticles as silicon solar cells coaters, showing their influence on the solar cells efficiency. Ceria nanoparticles can be synthesized to have formed oxygen vacancies (O-vacancies), which are associated with converting cerium ions from the Ce⁴⁺ state ions to the Ce³⁺ ones. These O-vacancies follow the rule of improving silicon solar cellconductivity through the hopping mechanism. Besides, under violet excitation, the reduced trivalent cerium Ce³⁺ ions are directly responsible for down-converting the un-absorbed violet or ultra-violet (UV) wavelengths to a resulted green fluorescence emission at ~520 nm. These are absorbed through the silicon solar cells active layer. When electrospun Poly(vinyl alcohol) (PVA) is embedded with ceria nanoparticles on the rear surface of silicon solar cell, a promising enhancement in the behavior of solar cells current–voltage (I–V) curve is observed. The efficiency has improved by about 24% of its initial value due to the mutual impact of improving both electrical conductivity and optical conversions from the higher surface-to-volume ratio of electrospun nanofibers embedded by ceria nanoparticles. The solar cell efficiency improvement is due to the mutual impact of both optical down-conversion and better electric paths via the used nanocomposite. The added nanostructures coating can utilize part of the transmitted UV or violet spectrum through the cell as optical conversion from violet to the visible region. In addition, the formed active tri-valent states are associated with O-vacancies which can help in a better conductivity of the generated photoelectrons from the cell through the hopping mechanism. The PVA nanofibers host offers a better distribution of ceria nanoparticles and better conductivity paths for the photoelectrons based on the better surface-to-volume ratio of the nanofibers.