Down-shifting Si-based layer for Si solar applications

Abstract

International audienceSiNx and SiNx:Tb3+ thin layers were deposited by reactive magnetron co-sputtering with the objective of optimizing the light management in Si solar cells. Those Si-based layers are developed to be compatible with the Si-PV technology. An efficient energy transfer between SiNx matrix and terbium ions (Tb3+), enhancing this system absorption, has been demonstrated and optimized. The layer composition and microstructure as well as its optical properties have been analyzed with the aim of improving both its anti-reflective properties and its luminescence emission intensity. An optimized layer was obtained by co-sputtering of Si and Tb targets in a nitrogen rich atmosphere. The emission efficiency of the SiNx:Tb3+ layer is compared to the one of previously optimized SiOxNy:Tb3+ layer. Finally we show how SiNx:Tb3+ thin films may be integrated on top of Si solar cells and act simultaneously as a down-shifting layer and antireflective coating

First down converter multilayers integration in an industrial Si solar cell process

“…The comparison of the PL intensities evidences an increase of the emission in the multilayer structure by a factor 1.5. As previously described, the Yb 3+ PL intensity, I PL , is given by the relation: …”

“…For this purpose, the fabrication steps, ie, deposition and post annealing treatment, have been integrated in an industrial cell fabrication process. The process flow of monolithic c‐Si solar cells topped with DC layer has been previously described elsewhere and is schematically presented in inset of Figure . To fit the requirement of DC multilayer deposition due to the chamber geometry, samples needed to be cut into pieces.…”

“…This dipole-dipole interaction process is at the origin of the excitation of Tb 3+ ions even under nonresonant wavelength. 33 Such SiN x :Tb 3+ -Yb 3+ layer showing a high Yb 3+ photoluminescence (PL) peak intensity was obtained and found to transmit more photons to the Si substrate (considered as the solar cell) than a previous system studied SiO x N y :Tb 3+ -Yb 3+ 31 . This improvement was mainly attributed to the higher rare earth ions incorporation in the pure nitride layer without the detrimental clustering effect observed in rare earth doped sputtered oxide Si-based matrix.…”

“…For the two first points, we have recently evidenced that this is the defect states related energy levels in the bandgap of the SiN x host matrix such as silicon‐related defects, for example, which absorb the energetic photons and transfer the energy to the resonant energy levels of Tb 3+ ( 5 G 6 , 5 D 3 ‐ 7 F 6 , 5 D 3 ‐ 7 F 4 , 5 D 4 ‐ 7 F 6 ). This dipole‐dipole interaction process is at the origin of the excitation of Tb 3+ ions even under nonresonant wavelength …”

Effects of d0 and s2 cations on optical properties of silicate glasses

“…Coatings are applied either through a vapour deposition process [85] or a dip coating or spinning technique [67]. Minimising the reflective losses results in a greater intensity of photons available for PV energy generation.…”