Rapid thermal processing of CuInSe2 electroplated precursors for CuIn(S,Se)2-based thin film solar cells

International audienceDuring the elaboration of standard CISEL™cells, electroplated CuInSe2 precursors undergo a rapid thermal processing (RTP) in a sulfur-containing atmosphere to promote grain growth and enable sulfurization of the precursor. The aim of this work is to show how structural and morphological properties of the CuIn(S,Se)2-based solar cells can be modified with RTP parameters, namely temperature, heating rate, and sulfur addition. X-ray diffractograms show that the preferential (112) orientation of the electrodeposited CuInSe2 precursor is maintained after annealing but the coefficient of crystallographic texture can be modified with specific RTP parameters. It is also shown that the quantity of sulfur incorporated in the chalcopyrite lattice can be controlled and reaches almost pure CuInS2 according to the sulfur quantity used during the RTP. Another effect of the RTP annealing is to form a Mo(S,Se)2 layer which can lead to a quasi-ohmic contact between the molybdenum and the absorber. The properties of the Mo(S,Se)2 buffer layer are also studied according to the process parameters and an increase of the annealing temperature or of the sulfur concentration tends to increase the thickness of this laye

Electrochemical determination of acidity level and dissociation of formic acid-water mixtures as solvent

International audienceThe autoprotolysis constant KHS of formic acid/water mixtures as solvent has been calculated from acid-base potentiometric titration curves. A correlation of the acidity scale pKHS of each medium versus pure water has been implemented owing to the Strehlow R0(H+) lectrochemical redox function. The results show that formic acid/water mixtures are much more dissociated than pure water; such media are sufficiently dissociated to allow electrochemical measures without addition of an electrolyte. It has also been shown that for a same H+ concentration the activity of protons increases with formic acid concentration. For more than 80 wt.% of formic acid the acidity is sufficiently increased to locate the whole acidity scale pKHS in the super acid medium of the generalized acidity scale pHH2O

Sulfurization of Cu-In electrodeposited precursors for CuInS2-based solar cells

International audienceCu-In electrodeposited layers were annealed using rapid thermal processing (RTP) in a reactive atmosphere containing sulfur vapors. The CuInS2 formation mechanism during sulfurization of electrodeposited precursors proceeds mainly through direct sulfurization of the metallic Cu-In alloy, forming spinel CuIn5S8 and chalcopyrite CuInS2 ternary phases. During the heating step, the Cu-In metallic alloy gets richer in copper as the temperature increases and transforms from CuIn2 to Cu11In9, then Cu16In9 and finally to Cu7In3. The use of rapidly cooled samples stopped after different durations of the process along with ex-situ XRD analysis enabled us to differentiate the Cu16In9 and Cu7In3 phases. Finally, the efficiency of the solar cells made with the two-step electrodeposition and RTP low-cost process reaches 11% (active area 0.421 cm2), which is close to the results obtained for cells made with PVD precursors

Key role of Cu–Se binary phases in electrodeposited CuInSe2 precursors on final distribution of Cu–S phases in CuIn(S,Se)2 absorbers

International audienc

Pseudorapidity densities of charged particles with transverse momentum thresholds in pp collisions at √ s = 5.02 and 13 TeV

The pseudorapidity density of charged particles with minimum transverse momentum (pT) thresholds of 0.15, 0.5, 1, and 2 GeV/c is measured in pp collisions at the center of mass energies of √s=5.02 and 13 TeV with the ALICE detector. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity (η) within 0.8pT larger than the corresponding threshold. In addition, measurements without pT-thresholds are performed for inelastic and nonsingle-diffractive events as well as for inelastic events with at least one charged particle having |η|2GeV/c), highlighting the importance of such measurements for tuning event generators. The new measurements agree within uncertainties with results from the ATLAS and CMS experiments obtained at √s=13TeV.

Two-particle transverse momentum correlations in pp and p–Pb collisions at energies available at the CERN Large Hadron Collider

Two-particle transverse momentum differential correlators, recently measured in Pb--Pb collisions at energies available at the CERN Large Hadron Collider (LHC), provide an additional tool to gain insights into particle production mechanisms and infer transport properties, such as the ratio of shear viscosity to entropy density, of the medium created in Pb-Pb collisions. The longitudinal long-range correlations and the large azimuthal anisotropy measured at low transverse momenta in small collision systems, namely pp and p-Pb, at LHC energies resemble manifestations of collective behaviour. This suggests that locally equilibrated matter may be produced in these small collision systems, similar to what is observed in Pb-Pb collisions. In this work, the same two-particle transverse momentum differential correlators are exploited in pp and p-Pb collisions at s√=7 TeV and sNN−−−√=5.02 TeV, respectively, to seek evidence for viscous effects. Specifically, the strength and shape of the correlators are studied as a function of the produced particle multiplicity to identify evidence for longitudinal broadening that might reveal the presence of viscous effects in these smaller systems. The measured correlators and their evolution from pp and p--Pb to Pb--Pb collisions are additionally compared to predictions from Monte Carlo event generators, and the potential presence of viscous effects is discussed

Measurements of the groomed jet radius and momentum splitting fraction with the soft drop and dynamical grooming algorithms in pp collisions at √s = 5.02 TeV

This article presents measurements of the groomed jet radius and momentum splitting fraction in pp collisions at s√=5.02 TeV with the ALICE detector at the Large Hadron Collider. Inclusive charged-particle jets are reconstructed at midrapidity using the anti-kT algorithm for transverse momentum 60<pchjetT<80 GeV/c. We report results using two different grooming algorithms: soft drop and, for the first time, dynamical grooming. For each grooming algorithm, a variety of grooming settings are used in order to explore the impact of collinear radiation on these jet substructure observables. These results are compared to perturbative calculations that include resummation of large logarithms at all orders in the strong coupling constant. We find good agreement of the theoretical predictions with the data for all grooming settings considered