Thin-film of Nd3+–Yb3+ co-doped low silica calcium aluminosilicate glass grown by a laser deposition technique

Abstract

Recent theory has predicted that spectral converters would be a promising pathway to improve the spectral response of silicon solar cells. As a consequence, new materials and methods of coupling these sensitizers in photovoltaic cells have been investigated. In this work, a UV pulsed laser deposition technique was used to grow thin films of Nd3+–Yb3+ co-doped low silica calcium aluminosilicate glass on silicon substrates, aiming for the development of hybrid solar cells with spectral converters. The role of both laser shots and substrate temperature was investigated, as well as the film's optical and structural properties. Our films present no crystalline order (amorphous) and present a surface with a roughness of the order of sub-nanometers. Significant flat regions between grains were observed by AFM analyses. Photoacoustic spectroscopy was successfully developed to determine the thicknesses of thin films in a range higher than the limit of the x-ray reflectivity technique (≥170 nm). From 1000 to 20 000 laser shots, the film thicknesses increased from 27 to 680 nm. The photoluminescence measurements demonstrated efficient energy transfer processes toward the Yb3+ 950–1200 nm emission, suggesting this material as a promising spectral converter for the development of hybrid solar cells.