Nanooptics and photonics

First rare earth ions doped Si based down converter layers integration in an industrial Si solar cell
J. Cardin1, L. Dumont1, C. Labbé1, P.-M. Anglade1 , M. Vallet2, M. Carrada2, S.C. Wu3, I.-S. Yu3, A. L. Richard4, W. M. Jadwisienczak4, X. Portier1, P. Marie1, F. Gourbilleau1
1 CIMAP, Normandie Univ, ENSICAEN, UNICAEN, CEA, CNRS, 6 Boulevard Maréchal Juin 14050 Caen Cedex 4, France, E-mail: Julien.cardin@ensicaen.fr
2 CEMES-CNRS, Université de Toulouse, 29 rue J. Marvig, 31055 Toulouse Cedex 04
3 Department of Materials Science and Engineering, National Dong Hwa University, Hualien, Taiwan
4 Ohio University, Athens, OH 45701, USA
One of the most promising approaches to increase the Silicon Solar Cell (SC) efficiency is its combination with frequency conversion (FC) layers. This additional layer spectrally redistributes irradiance in order to obtain a larger spectral overlapping between the resulting irradiance and the Si-SC absorptivity and therefore may increase efficiency at the expense of the thermalization of photogenerated carriers. FC is either a Down Conversion (DC) or a Down Shifting (DS) when direct sun irradiance is converted or Up Conversion (UC) when the irradiance already transmitted through the SC is converted. Those conversions using absorption and emission of trivalent Rare Earth (RE) ions are either based on couples of ions such as Tb3+(Pr3+)-Yb3+ for DC process or on ions such as Pr3+ or Tb3+ for the DS process. Regrettably, RE ions low excitability and the chemical incompatibility of usual RE host matrix with Si-SC are major disadvantages to their usage. The purpose of this paper is to present the study of DC (DS) layers, which consist in a Si-based matrix doped with Tb3+-Yb3+ ions fabricated by a co-sputtering approach. DC (DS) layers were structurally and optically characterized and the resulting conversion efficiency was estimated [1,2,3]. Modelling by means of Monte-Carlo approach and by rate equations model allowed us to better understand the role of RE ions interdistances on the energy transfer mechanism and consequently on the efficiency of the conversion[4]. We successfully integrated our SiNx Tb3+-Yb3+ DC layer on a silicon based SC [4,5] and determined a relative efficiency improvement up to 1.34%.
1.	SiNx: Tb3+–Yb3+, an efficient down-conversion layer compatible with a silicon solar cell process, L. Dumont et al, Solar Energy Materials and Solar Cells 145, 84-92, 2016 
2.	Frequency Conversion Layers for Si Solar Cell Efficiency Improvement in Frontiers in Electronic Technologies, F. Gourbilleau et al., Springer, Singapore, 85-91, 2017
3.	Down-shifting Si-based layer for Si solar applications, L. Dumont et al, Solar Energy, Materials and Solar Cells 169, 132-144, 2017
4.	First down converter multilayers integration in an industrial Si solar cell process, L. Dumont et al., Progress in Photovoltaics: Research and Application, 27, 2, 152-162, 2019
5.	Monolithic crystalline silicon solar cells with SiNx layers doped with Tb3+ and Yb3+ rare-earth ions, Ing Song Yu, et al, Journal of Rare Earths, 37,5, 515-519, 2019