Iron pyrite (FeS(2)) is a naturally abundant and nontoxic photovoltaic material that can potentially make devices as efficient as silicon-based ones; however existing iron pyrite photovoltaic devices contain thermodynamically unstable FeS(2) film surfaces that lead to low open circuit voltages. We report the rational synthesis of phase pure, highly crystalline cubic FeS(2) nanocrystals (NCs) using a trioctylphosphine oxide (TOPO) assisted hot-injection method. The synthesized pyrite NC films have excellent air stability over one year. In contrast, obvious surface decomposition was observed on the surface of FeS(2) NCs synthesized without TOPO. A high carrier mobility of 80 cm(2)/(V s) and a strong photoconductivity were observed for the first time for pyrite films at room temperature. Our results indicate that TOPO passivates both iron and sulfur atoms on FeS(2) NC surfaces, efficiently inhibiting surface decomposition.

Thermoelectric properties, X-ray photoelectron spectroscopy, Raman spectroscopy, and electronic structures have been studied for Mn-substituted CuInSe 2 chalcopyrites. Raman spectroscopy verifies the lattice disorder due to the introduction of Mn into the CuInSe 2 matrix, leading to a slight suppression of thermal conductivity. On the other hand, the Mn substitution significantly increases the electrical conductivity and Seebeck coefficient. Therefore the thermoelectric figure of merit, ZT, has been enhanced by over two orders of magnitude by the introduction of Mn into CuInSe 2 . These materials are p-type degenerate semiconductors, containing divalent Mn species as confirmed by X-ray photoelectron spectroscopy. The crystal structure of Mn-substituted CuInSe 2 , as well as related ternary and quaternary diamond-like semiconductors, can be viewed as a combination of an electrically conducting unit, the

Part of the Electrical and Computer Engineering CommonsOlejníček, J.; Kamler, Chad A.; Mirasano, A.; Martinez-Skinner, A. L.; Ingersoll, M. A.; Exstrom, C. L.; Darveau, S. A.; Huguenin-Love, J. L.; Diaz, M.; Ianno, Natale J.; and Soukup, Rodney J., "A non-vacuum process for preparing nanocrystalline CuIn 1−x Ga x Se 2 materials involving an open-air solvothermal reaction" (Abstract A non-vacuum, two-step process has been used to prepare a series of nanocrystalline CuIn 1−x Ga x Se 2 (x = 0, 0.25, 0.5, 0.75, 1) materials.An open-air solvothermal preparation in triethylenetetramine solvent was followed by annealing at 500 °C in a nitrogen atmosphere for 20 min. All materials have mixed clustered plate, spherical particle, and nanorod morphologies with the smallest particle diameters ranging between 20 and 40 nm. Raman spectroscopy and X-ray diffraction (XRD) confirm that indium/gallium ratio control is possible over a wide range. The solvothermal reaction step yields a mixture of chalcopyrite and Cu 2−x Se. This is converted to pure chalcopyrite product by annealing at 500 °C.

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