Sputter deposited transition metal nitrides as back electrode for CIGS solar cells

Abstract

4add to my program 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. 5add to my program EMRS -Strasbourg

Study on reactive sputtering of yttrium oxide: Process and thin film properties

“…A difference between the high energy species bombarding the target is of importance. Indeed as shown by S. Mahieu et al [45,46] there is a clear relationship between the momentum flux and the film density. In poisoned mode the contribution of reflected neutrals can be ruled out, as the average mass of the atoms in the top layer will drastically decrease.…”

Optimisation of rear reflectance in ultra-thin CIGS solar cells towards >20% efficiency

“…Some studies have already shown that replacing molybdenum with gold or silver improve the rear reflectance, thus increasing the cell performances (Dahan et al, 2012;Li-Kao et al, 2012). Other metals like W, Cr or Ta (Orgassa et al, 2003a), zirconium nitride (ZrN) (Krc et al, 2016;Schleussner et al, 2009) or titanium nitride (TiN) (Mahieu et al, 2011) have been tested and have shown good results. The backwall supersaturate structure, where the glass substrate is used as the front-part of the device, gives an other effective alternative to improve ultra-thin film solar cell performances by using silver (Ag) reflector on the rear side (Larsen et al, 2014;Simchi et al, 2014).…”

Three-dimensional kinetic Monte Carlo simulations of cubic transition metal nitride thin film growth

“…Transition metal nitrides (TMNs) belonging to group IV-VI are a fascinating class of materials which offer, due to their unique combination of metallic, ionic, and covalent bonding, a broad range of applications in manufacturing, semiconductor, optoelectronic, plasmonic, and photovoltaics industries [1][2][3][4][5][6]. Their refractory character imparts high hardness [7][8][9], chemical inertness, and thermal stability up to 1000 • C for specific alloys [10][11][12], which make them widely used as protective and wear-resistant coatings for cutting tools [1].…”