(Invited) Luminescence of Rare Earth Doped Si Based Nanofilms for LED and Photovoltaic Applications
Authors: Ehre Florian , Cardin Julien , Dufour Christian , Gourbilleau Fabrice , Portier Xavier , Frilay Cédric , Marie Philippe , Khomenkova Larysa , Rinnert Hervé , Lagarde Delphine , Marie Xavier , Jadwisienczak Wojciech , Ingram David C. , Yu Ing-Song , Labbé Christophe 
Published: May 2020

Rare earth (RE) doped silicon host matrices have been largely investigated to produce their luminescence's at different wavelengths for many applications such as Light Emitting Diode (LED) or frequency conversion layer to improve Solar Cells (SCs) efficiency. To achieve such a goal, RE ions-doped silicon oxynitride-based (SiOxNy) films have been deposited by reactive magnetron co-sputtering. A oxynitride host matrix allows a high RE ions incorporation while avoiding the clustering effect observed in silicon oxide host matrix.
In a first step, two different RE, Tb3+ and Ce3+, have been investigated. The Tb3+ ions present intra 4f transitions, whereas the Ce3+ ions have 4f-5d transitions. [1] These two different electronic configurations are investigated by means of luminescence spectroscopy. Indeed, the first step of this work is motivated by achieving an intense emission of Tb3+ and Ce3+ ions by optimizing the deposition parameters. The SiOxNy: RE layers were deposited on silicon substrates by using RF magnetron sputtering technique under N2 reactive flow, with a typical thickness of 20-50 nm. A deep investigation is performed to obtain an intense Ce3+ photoluminescence signal according to the Ce and N concentrations. Up to 6 at. % of Ce3+, no saturation of the PL intensity has been observed, demonstrating the absence of Ce clusters and/or silicate phase formation thanks to the nitrogen content. The influence of the nitrogen on current injection will be presented and the electroluminescence (EL) properties (I-V characteristic, EL spectra) will be analyzed.[2]

In a second step, down-converter (DC) layers compatible with the silicon industry which absorb UV photons and convert them into IR ones at an energy just above the Si band gap, were developed, taking account these two donors Tb3+ and Ce3+ and as acceptor the Yb3+ ion. Two different co-doping have been chosen i.e. Tb3+-Yb3+ and Ce3+-Yb3+ with the aim at obtaining an intense emission of the Yb3+ at 980 nm (1.265 eV). Furthermore the excitation mechanisms of acceptor ions Yb3+ will be discussed in both cases. [3, 4] At last, efficiency measurements with our DC layers on homemade and industrial Si-SCs have been carried out.[5]

[1] C. Labbé, Y.T. An, G. Zatryb, X. Portier, A. Podhorodecki, P. Marie, C. Frilay, J. Cardin, F. Gourbilleau, Structural and emission properties of Tb3+-doped nitrogen-rich silicon oxynitride films, Nanotechnology, 28 (2017) 115710-115714.

[2] F. Ehre, C. Labbé, C. Dufour, W. Jadwisienczak, J. Weimmerskirch-Aubatin, X. Portier, J.-L. Doualan, J. Cardin, A. Richard, D.C. Ingram, C. Labrugère, F. Gourbilleau, Nitrogen concentration effect on Ce doped SiOxNy emission: towards optimized Ce3+ for DEL application Nanoscale, 20 (2018) 4818-4830.

[3] Y.-T. An, C. Labbé, M. Morales, F. Gourbilleau, Highly efficient infrared quantum cutting in Tb3+-Yb3+ codoped silicon oxynitride for solar cell applications, Advanced Optical Materials, 1 (2013) 855-862.

[4] L. Dumont, P. Benzo, J. Cardin, I.S. Yu, C. Labbé, P. Marie, C. Dufour, G. Zatryb, A. Podhorodecki, F. Gourbilleau, Down-shifting Si-based layer for Si solar applications, Solar Energy Materials and Solar Cells, 169 (2017) 132-144.

[5] L. Dumont, J. Cardin, C. Labbé, C. Frilay, P.-M. Anglade, I.S. Yu, M. Vallet, P. Benzo, M. Carrada, D. Stiévenard, H. Mérabet, F. Gourbilleau, First Down Converter multilayers integration in an industrial Si solar cell process, Progress in Photovoltaics: Research and Applications, 27 (2018) 152-162.