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11:00Sputter deposited transition metal nitrides as back electrode for CIGS solar cells Authors : W.P. Leroy, S. Mahieu, D. Depla Research Group DRAFT, Dept. Solid State Sciences, Ghent University Resume : Thin Film solar cells exhibit many advantages over their crystalline counterpart, as e.g. the possibility to apply them to flexible and light-weight substrates. Due to the small thickness of the active layers (and hence only a limited material usage), these solar cells can be produced at a relatively low price, which also gives them advantages in many applications. A possibility to decrease the thickness of the absorber layers is the use of back electrodes which exhibit a high reflectivity in the red and near-infrared region. This would enable to compensate for the absorption losses (and hence a lower efficiency), when the absorber thickness is decreased. Metal foils (stainless steel, Ti or Cu foils) are often used as flexible substrate for the fabrication of the thin film solar cells, as these foils can withstand the relatively high temperatures which are often needed during the fabrication process. However, impurities coming from the metal foils, tend to diffuse into the absorber layer, causing a reduced efficiency of the absorber layer. Transition metal nitrides are known to have good barrier properties and a high thermal stability. Additionally, they have well known electronic properties which predict a good influence on the performance of the solar cell. This work deals with transition metal nitrides (TiN, ZrN) grown via reactive magnetron sputter deposition, where several deposition conditions (total pressure, N2 partial pressure, target-substrate distance and the type of noble gas) were varied. Through a thorough determination of the substrate fluxes such as the total energy flux and the momentum flux, a correlation to the thin film properties is sought. This will allow for a better control and an improved deposition of highly reflective transition metal nitrides. As a second step, the diffusion barrier properties at higher temperatures were investigated on some metal foils.
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EMRS -Strasbourg