IR-Luminescent PbS−Polystyrene Nanocomposites Prepared from Random Ionomers in Solution

Structural design considerations of solution-processable graphenes as interfacial materials via a controllable synthesis method for the achievement of highly efficient, stable, and printable planar perovskite solar cells

Solution-processable graphenes (represented by reduced graphene oxides, rGOs) have shown promising abilities as HTLs in perovskite solar cells (PeSCs). However, there has been no attempt to systematically tailor the characteristics of rGOs to the specifications of PeSCs. Furthermore, the applications of rGO HTLs have been limited to the spin-coating system, which is incompatible with roll-to-roll manufacturing. Here, with the aid of a polymer-graphene hybrid structure and a controllable synthesis method, we successfully developed a much more feasible rGO HTL and demonstrated highly efficient, stable, and printable p-i-n planar PeSCs with facile one-step processing. The characteristics of the developed polyacrylonitrile-grafted rGOs (PRGOs) were optimized by varying the synthesis conditions including the γ-radiation intensity (200, 400, and 600 kGy) and the concentration of the acrylonitrile (AN) precursor (2, 4, and 6 wt%). It is revealed that the PRGO synthesized with a lower AN concentration and a higher irradiation intensity (PRGO_2-600) is the most suitable one for PeSC HTL. PRGO_2-600 effectively raises the average power conversion efficiencies (PCEs) of PeSCs by ∼36% compared to those of conventional PeSCs using PEDOT:PSS HTL. The comprehensive investigations confirm that the enhanced device efficiency stems from (1) the favorable interlayer characteristics of the PRGO itself and (2) the well-crystallized perovskite layer grown on the PRGO. In addition to the PCE, thechemically inert PRGOs can also maintain their electrical properties over time and retard the decomposition of perovskite films, thereby prolonging the operation time of PeSCs in the atmosphere. More importantly, the applicability of the PRGO HTL is clearly verified even in the roll-to-roll compatible slot-die coating system, exhibiting comparable performances to those of the spin-coating system.

Dip-coated PbS/PVP nanocomposite films with tunable band gap

PbS/PVP nanocomposite films with tunable band gap from 0.8 to 1.92 eV.

Fabrication of composite polymer foam films at the liquid/liquid interface through emulsion-directed assembly and adsorption processes

The foam films of polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-b-PAA-b-PS) doped with Cd(II) or Pb(II) species were fabricated at the planar liquid/liquid interfaces between a DMF/chloroform (v/v: 1/1) solution of the polymer and aqueous solutions containing cadmium acetate or lead acetate at ambient temperature. Optical microscopic observation shows the thin film is uniform on a larger length scale. Transmission electron microscopic (TEM) investigations reveal that the foam films are made up of microcapsules with the size of several hundreds of nanometers to micrometers. The walls of the microcapsules have a layered structure decorating with nanofibers and hollow nanospheres, where numerous inorganic fine nanoparticles are dispersed homogeneously. The film formation is a result of emulsion droplet-templated assembly and adsorption of the formed microcapsules at the planar liquid/liquid interface. Because of the miscibility of DMF with chloroform and water, DMF migrates to the aqueous phase while water migrates to the organic phase across the interface, resulting in the formation of a W/O emulsion, as revealed by optical microscopic observation, freeze fracture transmission electron microscopic (FF-TEM) observation, and dynamic laser scattering (DLS) investigation. The triblock copolymer molecules and the inorganic species adsorb and self-assemble around the emulsion drops, leading to the formation of the composite microcapsules. X-ray photoelectron spectroscopic (XPS) and FTIR spectroscopic results indicate that two kinds of Cd(II) or Pb(II) species, metal oxide or hydroxide, resulting from the hydrolysis of the metal ions and the coordinated metal ions to the carboxyl groups coexist in the formed thin films, which transform to metal sulfide completely after treating with hydrogen sulfide to get metal sulfide nanoparticle-doped polymer thin films.

Infrared-emitting colloidal nanocrystals: synthesis, assembly, spectroscopy, and applications

Semiconductor nanocrystals produced by means of colloidal chemistry in a solvent medium are an attractive class of nanometer-sized building blocks from which to create complex materials with unique properties for a variety of applications. Their optical and electronic properties can be tailored easily, both by their chemical composition and particle size. While colloidal nanocrystals emitting in the infrared region have seen a burst of attention during the last decade there is clearly a paucity of review articles covering their synthesis, assembly, spectroscopic characterization, and applications. This Review comprehensively addresses these topics for II-VI, III-V, and IV-VI nanocrystals, examples being HgTe and Cd(x)Hg(1-) (x)Te, InP and InAs, and PbS, PbSe, and PbTe, respectively. Among the applications discussed here are optical amplifier media for telecommunications systems, electroluminescence devices, and noninvasive optical imaging in biology.

Sonochemical synthesis of hollow PbS nanospheres

PbS hollow nanospheres with diameters of 80-250 nm have been synthesized by a surfactant-assisted sonochemical route. The nanostructures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), (high-resolution) transmission electron microscopy [(HR)TEM], and scanning electron microscopy (SEM) images. Structural characterization indicates that shells of the hollow spheres are composed of PbS nanoparticles with diameters of about 12 nm. The formation of the hollow nanostructure was explained by a vesicle-template mechanism, in which sonication and surfactant play important roles. Furthermore, uniform silica layers were successfully coated onto the hollow spheres via a modified Stöber method to enhance their performance for promising applications.