Chalcopyrite copper indium sulfide (CuInS2) and copper indium gallium selenide (Cu(InxGa(1-x))-Se2; CIGS) nanocrystals ranging from approximately 5 to approximately 25 nm in diameter were synthesized by arrested precipitation in solution. The In/Ga ratio in the CIGS nanocrystals could be controlled by varying the In/Ga reactant ratio in the reaction, and the optical properties of the CulnS2 and CIGS nanocrystals correspond to those of the respective bulk materials. Using methods developed to produce uniform, crack-free micrometer-thick films, CulnSe2 nanocrystals were tested in prototype photovoltaic devices. As a proof-of-concept, the nanocrystal-based devices exhibited a reproducible photovoltaic response.

We report a chemical route to colloidal silicon (Si) nanocrystals, or quantum dots, with widely tunable average diameter, from less than 3 nm up to 90 nm and peak photoluminescence (PL) from visible wavelengths to the bulk band gap of Si at 1100 nm. The synthesis relies on the high temperature (>1100 °C) decomposition of hydrogen silsesquioxane (HSQ) to obtain Si quantum dots with good crystallinity and a narrow size distribution with tunable size embedded in SiO 2 . The oxide matrix is removed by hydrofluoric acid etching in the dark. Subsequent thermal hydrosilylation with alkenes yields free, solvent-dispersible Si nanocrystals with bright PL. The relationship between PL energy and size, exhaustively characterized by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD), is reported.

Cu(2)ZnSnS(4) (CZTS) is a promising new material for thin-film solar cells. Nanocrystal dispersions, or solar paints, present an opportunity to significantly reduce the production cost of photovoltaic devices. This communication demonstrates the colloidal synthesis of CZTS nanocrystals and their use in fabricating prototype solar cells with a power conversion efficiency of 0.23% under AM 1.5 illumination.

A nonwoven fabric with paperlike qualities composed of silicon nanowires is reported. The nanowires, made by the supercritical-fluid-liquid-solid process, are crystalline, range in diameter from 10 to 50 nm with an average length of >100 μm, and are coated with a thin chemisorbed polyphenylsilane shell. About 90% of the nanowire fabric volume is void space. Thermal annealing of the nanowire fabric in a reducing environment converts the polyphenylsilane coating to a carbonaceous layer that significantly increases the electrical conductivity of the material. This makes the nanowire fabric useful as a self-supporting, mechanically flexible, high-energy-storage anode material in a lithium ion battery. Anode capacities of more than 800 mA h g(-1) were achieved without the addition of conductive carbon or binder.

We show a method to produce biocompatible polymer-coated silicon (Si) nanocrystals for medical imaging. Silica-embedded Si nanocrystals are formed by HSQ thermolysis. The nanocrystals are then liberated from the oxide and terminated with Si-H bonds by HF etching, followed by alkyl monolayer passivation by thermal hydrosilylation. The Si nanocrystals have an average diameter of 2.1 ± 0.6 nm and photoluminesce (PL) with a peak emission wavelength of 650 nm, which lies Correspondence to: Brian A. Korgel, korgel@che.utexas.edu. NIH Public AccessAuthor Manuscript Small. Author manuscript; available in PMC 2011 September 20.