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The currently most efficient polycrystalline solar cells are based on the Cu(In,Ga)Se compound as a light absorption layer. However, in view of new concepts of nanostructured solar cells, CuInSe nanostructures are of high interest. In this work, we report CuInSe nanodots grown through a vacuum-compatible co-evaporation growth process on an amorphous surface. The density, mean size, and peak optical emission energy of the nanodots can be controlled by changing the growth temperature. Scanning transmission electron microscopy measurements confirmed the crystallinity of the nanodots as well as chemical composition and structure compatible with tetragonal CuInSe. Photoluminescence measurements of CdS-passivated nanodots showed that the nanodots are optoelectronically active with a broad emission extending to energies above the CuInSe bulk bandgap and in agreement with the distribution of sizes. A blue-shift of the luminescence is observed as the average size of the nanodots gets smaller, evidencing quantum confinement in all samples. By using simple quantum confinement calculations, we correlate the photoluminescence peak emission energy with the average size of the nanodots., The authors would like to acknowledge the CAPES (CAPESINL 04/14), CNPq, and FAPEMIG funding agencies for financial support. We acknowledge the collaboration project with IMM-CSIC (AIC-B-2011-0806). P. M. P. S. acknowledges financial support from EU through the FP7 Marie Curie IEF 2012 Action No. 327367. The projects RECI/FIS-NAN/0183/ 2012 (COMPETE: FCOMP-01-0124-FEDER-027494) and UID/CTM/50025/2013 from the Fundação para a Ciência e a Tecnologia (Portugal) and the project Nanotechnology Based Functional Solutions (NORTE-01-0145-FEDER-000019) are also acknowledged.

The currently most efficient polycrystalline solar cells are based on the Cu(In,Ga)Se2 compound as a light absorption layer. However, in view of new concepts of nanostructured solar cells, CuInSe2 nanostructures are of high interest. In this work, we report CuInSe2 nanodots grown through a vacuum-compatible co-evaporation growth process on an amorphous surface. The density, mean size, and peak optical emission energy of the nanodots can be controlled by changing the growth temperature. Scanning transmission electron microscopy measurements confirmed the crystallinity of the nanodots as well as chemical composition and structure compatible with tetragonal CuInSe2. Photoluminescence measurements of CdS-passivated nanodots showed that the nanodots are optoelectronically active with a broad emission extending to energies above the CuInSe2 bulk bandgap and in agreement with the distribution of sizes. A blue-shift of the luminescence is observed as the average size of the nanodots gets smaller, evidencing quantum confinement in all samples. By using simple quantum confinement calculations, we correlate the photoluminescence peak emission energy with the average size of the nanodots.