“It Keeps Going and Going and Going”: The Expansion of False Advertising Litigation Under the Lanham Act

To improve the conduction band alignment and explore the influence of the buffer-absorber interface, we here investigate an alternative buffer for Cu2ZnSnS4 (CZTS) solar cells. The Zn(O, S) system was chosen since the optimum conduction band alignment with CZTS is predicted to be achievable, by varying oxygen to sulfur ratio. Several sulfur to oxygen ratios were evaluated to find an appropriate conduction band offset. There is a clear trend in open-circuit voltage Voc, with the highest values for the most sulfur rich buffer, before going to the blocking ZnS, whereas the fill factor peaks at a lower S content. The best alternative buffer cell in this series had an efficiency of 4.6% and the best CdS reference gave 7.3%. Extrapolating Voc values to 0 K gave activation energies well below the expected bandgap of 1.5 eV for CZTS, which indicate that recombination at the interface is dominating. However, it is clear that the values are affected by the change of buffer composition and that increasing sulfur content of the Zn(O, S) increases the activation energy for recombination. A series with varying CdS buffer thickness showed the expected behavior for short wavelengths in quantum efficiency measurements but the final variation in efficiency was small

Dynamic parameter estimation of atomic layer deposition kinetics applied to in situ quartz crystal microbalance diagnostics

This paper presents the elaboration of an experimentally validated model of a continuous cross-flow atomic layer deposition (ALD) reactor with temporally separated precursor pulsing encoded in the Modelica language. For the experimental validation of the model, in situ quartz crystal microbalance (QCM) diagnostics was used to yield submonolayer resolution of mass deposition resulting from thin film growth of ZnO from Zn(C2H5)2 and H2O precursors. The ZnO ALD reaction intrinsic kinetic mechanism that was developed accounted for the temporal evolution of the equilibrium fractional surface concentrations of precursor adducts and their transition states for each half-reaction. This mechanism was incorporated into a rigorous model of reactor transport, which comprises isothermal compressible equations for the conservation of mass, momentum and gas-phase species. The physically based model in this way relates the local partial pressures of precursors to the dynamic composition of the growth surface, and ultimately governs the accumulated mass trajectory at the QCM sensor. Quantitative rate information can then be extracted by means of dynamic parameter estimation. The continuous operation of the reactor is described by limit-cycle dynamic solutions and numerically computed using Radau collocation schemes and solved using CasADi's interface to IPOPT. Model predictions of the transient mass gain per unit area of exposed surface QCM sensor, resolved at a single pulse sequence, were in good agreement with experimental data under a wide range of operating conditions. An important property of the limit-cycle solution procedure is that it enables the systematic approach to analyze the dynamic nature of the growth surface composition as a function of process operating parameters. Especially, the dependency of the film growth rate per limit-cycle on the half-cycle precursor exposure dose and the process temperature was thoroughly assessed and the difference between ALD in saturating and in non-saturating film growth conditions distinguished

Se-2 solar cells

Abstract We investigate reactively sputtered films of zirconium nitride, ZrN, for use as highly reflecting back contacts in Cu(In,Ga)Se 2 (CIGS) devices with sub-micrometer absorbers. We identify the nitrogen flow and the sputter current as the decisive parameters for the composition, and demonstrate a method for determining the nitrogen flow at which the transition from metallic to compound sputtering mode occurs for a given current. Films prepared at this working point consist of stoichiometric ZrN with a low resistivity, a high reflectance for red and infrared light, and have a fairly high sputter rate. Calculations show that the reflectance at the ZrN/CIGS interface is significantly superior to that at the standard Mo/CIGS interface

Low temperature (Zn,Sn)O deposition for reducing interface open-circuit voltage deficit to achieve highly efficient Se-free Cu(In,Ga)S2 solar cells

Cu(In,Ga)S-2 holds the potential to become a prime candidate for use as the top cell in tandem solar cells owing to its tunable bandgap from 1.55 eV (CuInS2) to 2.50 eV (CuGaS2) and favorable electronic properties. Devices above 14% power conversion efficiency (PCE) can be achieved by replacing the CdS buffer layer with a (Zn,Mg)O or Zn(O,S) buffer layer. However, the maximum achievable PCE of these devices is limited by the necessary high heating temperatures during or after buffer deposition, as this leads to a drop in the quasi-Fermi level splitting (qFLs) and therefore the maximum achievable open-circuit voltage (V-OC). In this work, a low-temperature atomic layer deposited (Zn,Sn)O thin film is explored as a buffer layer to mitigate the drop in the qFLs. The devices made with (Zn,Sn)O buffer layers are characterized by calibrated photoluminescence and current-voltage measurements to analyze the optoelectronic and electrical characteristics. An improvement in the qFLs after buffer deposition is observed for devices prepared with the (Zn,Sn)O buffer deposited at 120 degrees C. Consequently, a device with a V-OC value above 1 V was achieved. A 14% PCE is externally measured and certified for the best solar cell. The results show the necessity of developing a low-temperature buffer deposition process to maintain and translate absorber qFLs to device V-OC

Cd and Cu interdiffusion in Cu(In,Ga)Se2/CdS hetero-interfaces

We report a detailed characterization of an industry-like prepared Cu(In,Ga)Se2 (CIGS)/CdS heterojunction by scanning transmission electron microscopy (STEM) and photoluminescence (PL). Energy dispersive x-ray spectroscopy (EDS) shows the presence of several regions in the CIGS layer that are Cu deprived and Cd enriched, suggesting the segregation of Cd-Se. Concurrently, the CdS layer shows Cd-deprived regions with the presence of Cu, suggesting a segregation of Cu-S. The two types of segregations are always found together, which, to the best of our knowledge, is observed for the first time. The results indicate that there is a diffusion process that replaces Cu with Cd in the CIGS layer and Cd with Cu in the CdS layer. Using a combinatorial approach we identified that this effect is independent of focused-ion beam sample preparation and of the TEM-grid. Furthermore, photoluminescence measurements before and after an HCl etch indicate a lower degree of defects in the post-etch sample, compatible with the segregates removal. We hypothesize that Cu2-xSe nanodomains react during the chemical bath process to form these segregates since the chemical reaction that dominates this process is thermodynamically favourable. These results provide important additional information about the formation of the CIGS/CdS interface.publishe

CdS and Zn1−xSnxOy buffer layers for CIGS solar cells

Thin film solar cells based on Cu(In,Ga)Se2 (CIGS), where just the buffer layer is changed, were fabricated and studied. The effects of two different buffer layers, CdS and ZnxSn1-xOy (ZnSnO), are compared using several characterization techniques. We compared both devices and observe that the ZnSnO-based solar cells have similar values of power conversion efficiency as compared to the cells with CdS buffer layers. The ZnSnO-based devices have higher values in the short-circuit current (Jsc) that compensate for lower values in fill factor (FF) and open circuit voltage (Voc) than CdS based devices. Kelvin probe force microscopy (KPFM) results indicate that CdS provides junctions with slightly higher surface photovoltage (SPV) than ZnSnO, thus explaining the lower Voc potential for the ZnSnO sample. The TEM analysis shows a poly-crystalline ZnSnO layer and we have not detected any strong evidence of diffusion of Zn or Sn into the CIGS. From the photoluminescence measurements, we concluded that both samples are being affected by fluctuating potentials, although this effect is higher for the CdS sample.publishe

Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency. (C) 2016 Author(s).Peer reviewe

Atomic Layer Deposition of Copper, Copper(I) Oxide and Copper(I) Nitride on Oxide Substrates

Thin films play an important role in science and technology today. By combining different materials, properties for specific applications can be optimised. In this thesis growth of copper, copper(I) oxide and copper(I) nitride on two different substrates, amorphous SiO2 and single crystalline α-Al2O3 by the so called Atomic Layer Deposition (ALD) techniques has been studied. This technique allows precise control of the growth process at monolayer level on solid substrates. Other characteristic features of ALD are that it produces films with excellent step coverage and good uniformity even as extremely thin films on complicated shaped substrates. Alternative deposition schemes were developed for the materials of interest. It was demonstrated that use of intermediate water pulses affected the deposition pathways considerably. By adding water, the films are thought to grow via formation of an oxide over-layer instead of through a direct reaction between the precursors as in the case without water. For growth of copper(I) nitride from Cu(hfac)2 and ammonia no film growth occurred without adding water to the growth process. The Cu3N films could be transformed into conducting copper films by post annealing. In copper growth from CuCl and H2 the water affected film growth on the alumina substrates considerably more than on the fused silica substrates. The existence of surface -OH and/or -NHx groups was often found to play an important role, according to both theoretical calculations and experimental results

Atomic Layer Deposition of Copper, Copper(I) Oxide and Copper(I) Nitride on Oxide Substrates

Thin films play an important role in science and technology today. By combining different materials, properties for specific applications can be optimised. In this thesis growth of copper, copper(I) oxide and copper(I) nitride on two different substrates, amorphous SiO2 and single crystalline α-Al2O3 by the so called Atomic Layer Deposition (ALD) techniques has been studied. This technique allows precise control of the growth process at monolayer level on solid substrates. Other characteristic features of ALD are that it produces films with excellent step coverage and good uniformity even as extremely thin films on complicated shaped substrates. Alternative deposition schemes were developed for the materials of interest. It was demonstrated that use of intermediate water pulses affected the deposition pathways considerably. By adding water, the films are thought to grow via formation of an oxide over-layer instead of through a direct reaction between the precursors as in the case without water. For growth of copper(I) nitride from Cu(hfac)2 and ammonia no film growth occurred without adding water to the growth process. The Cu3N films could be transformed into conducting copper films by post annealing. In copper growth from CuCl and H2 the water affected film growth on the alumina substrates considerably more than on the fused silica substrates. The existence of surface -OH and/or -NHx groups was often found to play an important role, according to both theoretical calculations and experimental results

Atomic Layer Deposition of Copper, Copper(I) Oxide and Copper(I) Nitride on Oxide Substrates

Thin films play an important role in science and technology today. By combining different materials, properties for specific applications can be optimised. In this thesis growth of copper, copper(I) oxide and copper(I) nitride on two different substrates, amorphous SiO2 and single crystalline α-Al2O3 by the so called Atomic Layer Deposition (ALD) techniques has been studied. This technique allows precise control of the growth process at monolayer level on solid substrates. Other characteristic features of ALD are that it produces films with excellent step coverage and good uniformity even as extremely thin films on complicated shaped substrates. Alternative deposition schemes were developed for the materials of interest. It was demonstrated that use of intermediate water pulses affected the deposition pathways considerably. By adding water, the films are thought to grow via formation of an oxide over-layer instead of through a direct reaction between the precursors as in the case without water. For growth of copper(I) nitride from Cu(hfac)2 and ammonia no film growth occurred without adding water to the growth process. The Cu3N films could be transformed into conducting copper films by post annealing. In copper growth from CuCl and H2 the water affected film growth on the alumina substrates considerably more than on the fused silica substrates. The existence of surface -OH and/or -NHx groups was often found to play an important role, according to both theoretical calculations and experimental results