CuInSe2 quantum dots grown by molecular beam epitaxy on amorphous SiO2 surfaces.

Henrique Limborço,Joaquim P Leitão,Juan C Gonzalez,Pedro Mp Salomé,Sascha Sadewasser,Kamal Abderrafi,Jennifer P Teixeira,Rodrigo Ribeiro-Andrade,Nicoleta Nicoara

doi:10.3762/bjnano.10.110

Abstract

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.

Highlights

The chalcopyrite compound Cu(In,Ga)Se2 (CIGS) is used as the light absorber layer in thin film solar cells that typically consist of a glass substrate, a Mo back contact, the CIGS layer, and aCdS/i-ZnO/ZnO:Al front contact
It is the first time that CIS nanodots were prepared in a single step under vacuum conditions on an amorphous substrate
The same analysis hints to a Cu-poor and Se-rich CIS wetting layer, but the effects, structure, and exact composition of this layer have to be studied in more detailed

Summary

Introduction

The chalcopyrite compound Cu(In,Ga)Se2 (CIGS) is used as the light absorber layer in thin film solar cells that typically consist of a glass substrate, a Mo back contact, the CIGS layer, and aCdS/i-ZnO/ZnO:Al front contact. The motivation behind the present work is to grow CIS nanodots on substrates covered with an amorphous layer using co-evaporation.

Results

Conclusion