Graphene: Polymer composites as moisture barrier and charge transport layer toward solar cell applications

Abstract: It is generally known that significant improvements in the properties of nanocomposites can be achieved with graphene types currently commercially available. However, so far this is only possible on a laboratory scale. Thus, the aim of this study was to transfer results from laboratory scale experiments to industrial processes. Therefore, nanocomposites based on polyamide (PA) and graphene nanoplatelets (GnP) were prepared in order to produce membranes with improved gas barrier properties, which are characterized by reduced permeation rates of helium. First, nanocomposites were prepared with different amounts of commercial availably graphene nanoplatelets using a semi-industrial-scale compounder. Subsequently, films were produced by compression molding at different temperatures, as well as by flat film extrusion. The extruded films were annealed at different temperatures and durations. In order to investigate the effect of thermal treatment on barrier properties in correlation to thermal, structural, and morphological properties, the films were characterized by differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), optical microscopy (OM), transmission electron microscopy (TEM), melt rheology measurements, and permeation measurements. In addition to structural characterization, mechanical properties were investigated. The results demonstrate that the permeation rate is strongly influenced by the processing conditions and the filler content. If the filler content is increased, the permeation rate is reduced. The annealing process can further enhance this effect.

Abstract: The recent years have seen numerous developments in the research and headway of graphene, the thinnest two-dimensional nuclear material. Graphene-based materials and their composites have promising applications in an extensive variety of fields; for example, gadgets, biomedical guides, films, adaptable wearable sensors, and actuators. The most recent investigations and movement in this branch of knowledge regularly deliver conflicting or uncertain outcomes. This article evaluates and outlines the distributed information in order to give a basic and complete diagram of the cutting edge. Initially, the particular basic nature of accessible graphene materials is illustrated as well as the distinctive generation methods accessible thus far. The appraisal at that point talks about the different composites that center diverse sub-practical routines; for example, mechanical and aggregate utilitarian applications (e.g., vitality, hardware biomedical, layers, and sensors). The use of graphene and its subsidiaries in the fabricate of nanocomposites with various polymer frameworks has been inspected. And finally, an ending and point of view are given to talking about the rest of the difficulties for graphene nanocomposites in useful science and building.

Abstract: In this study, black titanium dioxide (B–TiO2) nanoparticles were synthesised by the hydrogenation of white anatase TiO2 with the simultaneous formation of oxygen depletion regions. The oxygen deficient regions of B–TiO2 offer additional energy transport states, which accelerate electron extraction. The B–TiO2 nanoparticles were introduced into PC70BM as electron transport layer in an inverted perovskite solar cell. The optimised concentration of B–TiO2 improved the extraction and transport of the electrons, which led to an increased power-conversion efficiency than that of the reference device considered in this study (over 10% enhancement). The role of B–TiO2 in boosting the electron flow within the device has been elucidated using atomic force microscopy, reflectance, photoluminescence spectroscopy, space-charge-limited current mobility, and electrical impedance. Furthermore, the device stability was influenced by the water-repellent property arising from the self-orientation of PC70BM due to the difference in surface energy.

Abstract: Recently, polymer nanocomposites have become among the most effective approaches to creating multifunctional materials with significant improvement in their electrical, physical, and chemical properties. This nanocomposite material has been widely studied in both academia and industry due to its outstanding properties for various energy-related applications. Polymer nanocomposites based on silica, carbon nanotubes, graphene, boron nitride, and metal oxides are chosen for energy-related applications. Various synthesis methods to achieve polymer nanocomposites have been discussed. In addition, the surface morphological characteristics have been highlighted to realize the structure-property relationship. Finally, this chapter describes recent promising research on polymer nanocomposites for applications in supercapacitors, solar cells, lithium-ion batteries, lithium-sulfur batteries, lithium-air batteries, and fuel cells in detail, including the future scope of the study.

Abstract: The energy costs associated with separating tightly bound excitons (photoinduced electron-hole pairs) and extracting free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. We report a low-cost, solution-processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite.

Abstract: Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

Abstract: Within the space of a few years, hybrid organic–inorganic perovskite solar cells have emerged as one of the most exciting material platforms in the photovoltaic sector. This review describes the rapid progress that has been made in this area.

Abstract: Chemically derived graphene oxide (GO) is an atomically thin sheet of graphite that has traditionally served as a precursor for graphene, but is increasingly attracting chemists for its own characteristics. It is covalently decorated with oxygen-containing functional groups - either on the basal plane or at the edges - so that it contains a mixture of sp(2)- and sp(3)-hybridized carbon atoms. In particular, manipulation of the size, shape and relative fraction of the sp(2)-hybridized domains of GO by reduction chemistry provides opportunities for tailoring its optoelectronic properties. For example, as-synthesized GO is insulating but controlled deoxidation leads to an electrically and optically active material that is transparent and conducting. Furthermore, in contrast to pure graphene, GO is fluorescent over a broad range of wavelengths, owing to its heterogeneous electronic structure. In this Review, we highlight the recent advances in optical properties of chemically derived GO, as well as new physical and biological applications.

Abstract: Hybrid organic/inorganic perovskites (e.g., CH3NH3PbI3) as light absorbers are promising players in the field of third-generation photovoltaics. Here we demonstrate a low-temperature vapor-assisted solution process to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale. Solar cells based on the as-prepared films achieve high power conversion efficiency of 12.1%, so far the highest efficiency based on CH3NH3PbI3 with the planar heterojunction configuration. This method provides a simple approach to perovskite film preparation and paves the way for high reproducibility of films and devices. The underlying kinetic and thermodynamic parameters regarding the perovskite film growth are discussed as well.