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With the massive growth of the global capacity of photovoltaics (PV) over the last decade, the PV waste is expected to increase dramatically in the near future. Having potential to reduce the use of raw materials and preserve natural resources, PV recycling is attracting more and more attention. This being said, the environmental impacts over the life cycle of PV technologies, including the end-of-life (EoL) stage, should be evaluated carefully. Life cycle assessment (LCA) is currently the most common methodology to assess the potential environmental impacts of a product throughout its entire life cycle. However, the modelling of recycling in LCA has always been a challenge and no consensus has yet been reached, since the treatment of recycling does not only involve an EoL management of waste, but also the production of recycled material. Perovskite on silicon tandem is a widely investigated emerging PV technology having the potential to overcome the power conversion efficiency (PCE) limit of the single-junction crystalline silicon technology. The EoL modelling seems more challenging in the case of emerging technologies for which the EoL is more uncertain than for established technologies. In this article, six common and important approaches of EoL modelling in LCA were applied to future perovskite/silicon tandem modules to analyze the effect of the different EoL modelling approaches on the LCA results. The aim was to identify the most suitable methodological approaches to account for recycling, when modelling the life cycle of PV modules. The environmental performance of perovskite/silicon tandem modules was assessed over their life cycle and expressed in terms of impacts per m2 of module. After testing the six EoL modelling approaches and comparing the LCA results, the EoL modelling choice was found to lead to non-negligible differences. For example, in terms of climate change, the impact of the tandem modules ranges from 45 to 59 kg CO2-eq/m2. Among the six EoL modelling options, the approaches of simple cut-off and cut-off with economic allocation are more oriented towards the promotion of high rates of recycled material integrated as an input to the assessed product among industrial actors, while the approach of closed-loop allocation provides incentives to maximize the ratio of recycling at the EoL, regardless the initial ratio of recycled content within the product. Some approaches such as the circular footprint formula (CFF) tend to provide both incentives to increase the content of recycled input material in the manufacturing of the product and the recycling ratio at the EoL of such product. After applying the different alternatives, a set of recommendations to select the relevant EoL modelling approaches are provided: 1) the CFF is recommended as a representative approach due to its wide applicability, tending to provide an intermediate result and reflecting the characteristics of materials; 2) sensitivity analysis should be applied to check the robustness of the results, 3) the cut-off approach and the closed-loop allocation should be used at least for the sensitivity analysis.

Perovskite on silicon tandem technologies offer a promising way to overcome the efficiency limit of single-junction crystalline silicon modules and are therefore widely studied. Besides the cost reduction potential of using tandem modules in utility-scale PV plants, the application of bifacial PV modules offers additional opportunities to reduce costs by increasing the energy yield. However, the bifaciality factor of tandem PV modules using bifacial crystalline silicon solar cells is typically lower than that of single-junction bifacial modules, considering the asymmetric architecture of the module with higher front-side than rear-side efficiency. In this study, we assess a symmetrical bifacial triple-junction perovskite/silicon/perovskite PV module architecture which allows for a significant improvement of the PV module rear side efficiency. Cost of ownership, energy yield and levelized cost of energy modeling show the superior performance of such modules compared to crystalline silicon and perovskite/silicon tandem modules specifically in vertical mounting applications that are used e.g.in AgriPV or noise protection PV walls on highways.

The structural and electronic properties of nanocrystalline Si epitaxial layers at low temperatures are examined.

The capacitance behavior of metal insulator metal (MIM) structures with Zr1-xAlxO2 dielectrics and TiN metal electrodes is analyzed. The capacitance nonlinearity, the dielectric relaxation, and the loss phenomena are found to depend strongly on the Al content, the dielectric thickness, and the amorphous/crystalline phase of the dielectric layer. Two different kinds of phenomena—crystallization-related and interface-related, are considered to explain the observed results, especially the polarity asymmetry in the dielectric behavior. It is found that crystallization of the films enhances the effects of dielectric relaxation and loss, most likely due to charge trapping at grain boundaries. Further on, reactions between the oxidizing ambient (ozone) and the bottom electrode during high-k deposition result in structural changes (formation of TiOx interfacial layer) and thus in generation of defects which cause a different electrical behavior of the two TiN/Zr1-xAlxO2 interfaces at the top and the bottom electrode and a polarity asymmetry of the capacitance performance. [ABSTRACT FROM AUTHOR]

The capacitance behavior of metal insulator metal (MIM) structures with [Zr.sub.1-x][Al.sub.x][O.sub.2] dielectrics and TiN metal electrodes is studied. The reactions between the oxidizing ambient and the bottom electrode during high-k deposition has resulted in structural changes and thus in generation of defects that cause a different electrical behavior of the two TiN/[Zr.sub.1-x][Al.sub.x][O.sub.2] interfaces at the top and the bottom electrode and a polarity asymmetry of the capacitance performance.

HfTiO2 layers of various stoichiometries where deposited by physical vapor depostion on TiN and TiN/Ru bottom electrodes (BE) in order to determine the influence of composition, conduction band offset, and BE morphology on the overall leakage current characteristics. Current-voltage spectroscopy, transmission electron microscopy, electron energy loss spectroscopy, and conductive atomic force microscopy studies show increased leakage current and charge trapping with increased Ti content. The interplay of conduction band offset and trap density were studied. The influence of Ru bottom electrode roughness on the leakage current is higher than the influence of Ti content and low conduction band offset. [ABSTRACT FROM AUTHOR]

Abstract-Long-term reliability results over six orders of magnitude in time are presented showing that the voltage acceleration model for ZrO[sub2]/SiO[sub2]/ZrO[sub2] exhibits an exponential dependence with voltage, down to 2 V. The voltage acceleration parameter γ is between 10 and 15 V[sup-1], depending on the biasing polarity. Softbreakdown behavior (SILC) is evident prior to the onset of hard breakdown as a result of barrier lowering or charge accumulation in the high-k film. Under ac stress conditions, this SILC branch is lowered in magnitude, translating to a gain in lifetime to breakdown. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the deposition temperature and layer thickness on the physical and electrical properties of ZrO2-based high-k metal–insulator–metal (MIM) capacitors was studied. The increasing thickness of ZrO2 layer leads to decreasing the leakage current and capacitance of the device. The microstructure investigation shows that after the deposition of the complete MIM stack layer, all samples reveal similar degree of crystallinity, independent of the dielectric deposition temperature, hence it cannot explain completely the different electrical performance of the device. We found that the impurities concentration in the stack decreases as the deposition temperature increases. As a result, we obtain low leakage current (<10− 8 A/cm2) with highest k value(~43) for 8 nm ZrO2 layer deposited at a temperature of 275 °C. [Copyright &y& Elsevier]

Abstract: Atomic layer deposition was applied to fabricate metal oxide films on planar substrates and also in deep trenches with appreciable step coverage. Atomic layer deposition of Ru electrodes was realized on planar substrates. Electrical and structural behaviour of HfO2–TiO2 and Al2O3–TiO2 nanolaminates and mixtures as well as Al2O3 films were evaluated. The lowest leakage current densities with the lowest equivalent oxide thickness were achieved in mixed Al2O3–TiO2 films annealed at 700 °C, compared to all other films in as-deposited state as well as annealed at 900 °C. The highest permittivities in this study were measured on HfO2–TiO2 nanolaminates. [Copyright &y& Elsevier]