A cadmium-free CuInS2 quantum dot (QD)-sensitized solar cell (QDSC) has been fabricated by taking advantage of the ex situ synthesis approach for fabricating highly crystalline QDs and the in situ successive ionic-layer adsorption and reaction (SILAR) approach for achieving high surface coverage of QDs. The ex situ synthesized CuInS2 QDs can be rendered water soluble through a simple and rapid two-step method under the assistance of ultrasonication. This approach allows a stepwise ligand change from the insertion of a foreign ligand to ligand replacement, which preserves the long-term stability of colloidal solutions for more than 1 month. Furthermore, the resulting QDs can be utilized as sensitizers in QDSCs, and such a QDSC can deliver a power conversion efficiency (PCE) of 0.64%. Using the SILAR process, in situ CuInS2 QDs could be preferentially grown epitaxially on the pre-existing seeds of ex situ synthesized CuInS2 QDs. The results indicated that the CuInS2 QDSC fabricated by the combined ex situ/in situ growth process exhibited a PCE of 1.84% (short-circuit current density = 7.72 mA cm(-2), open-circuit voltage = 570 mV, and fill factor = 41.8%), which is higher than the PCEs of CuInS2 QDSCs fabricated by ex situ and in situ growth processes, respectively. The relative efficiencies of electrons injected by the combined ex situ/in situ growth approach were higher than those of ex situ synthesized CuInS2 QDs deposited on TiO2 films, as determined by emission-decay kinetic measurements. The incident photon-to-current conversion efficiency has been determined, and electrochemical impedance spectroscopy has been carried out to investigate the photovoltaic behavior and charge-transfer resistance of the QDSCs. The results suggest that the combined synergetic effects of in situ and ex situ CuInS2 QD growth facilitate more electron injection from the QD sensitizers into TiO2.

A synthetic route to CdTe/CdS and CdTe/CdSe core/shell type-II quantum dots in noncoordinating solvents (1-octadecene) was obtained. The results showed redshift in the emission spectra of CdTe/CdS and CdTe/CdSe compared with the CdTe core nanocrystals. This phenomenon is believed to indicate the formation of core/shell nanostructures. Transmission electron microscopy and powder x-ray diffraction were also consistent with nanocrystals containing a core of nearly monodisperse CdTe with CdS or CdSe capping. The photoluminescence quantum yield was enhanced by epitaxial growth of CdS or CdSe shells. Stepwise increasing concentration of sulfur or selenium monomers into the CdTe core solution allowed the examination of monomer activities, which are very relevant for synthesizing core/shell quantum dots.

Four novel red phosphorescent emitter compounds bis(1-phenylisoquinolinato-N,C 2' )iridium(acetylacetonate), (piq) 2 Ir(acac), bis(1-(1'-naphthyl)isoquinolinato-N,C 2' )iridium(acetylacetonate), (1-niq) 2 Ir(acac), bis(1-(2'naphthyl)isoquinolinato-N,C 2' )iridium(acetylacetonate), (2-niq) 2 Ir(acac) and bis(1-phenyl-5methylisoquinolinato-N,C 2' )iridium(acetylacetonate), (m-piq) 2 Ir(acac), have been synthesized and fully characterized. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ 3 /Al were fabricated. All devices emitted in the red region with an emission ranging from 624 to 680 nm. (m-piq) 2 Ir(acac) shows a maximum brightness of 17 164 cd m 22 at a current density of J ~300 mA cm 22 and the best luminance efficiency of 8.91 cd A 21 at a current density of J ~20 mA cm 22 . (1-niq) 2 Ir(acac) exhibits pure-red emission with 1931 CIE (Commission International de L'Eclairage) chromaticity coordinates x ~0.701, y ~0.273.

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