37 research outputs found
Additive-Free Near-Intrinsic Narrow Band Gap Perovskites via Sequential Thermal Evaporation: for Photovoltaic Applications
No full textTin/lead (Sn/Pb) iodide perovskites (PVKs) have emerged as promising absorber layer materials for high-efficiency tandem solar cells due to their low cost, high light absorption coefficients, and narrow band gaps. However, current solvent-based synthesis techniques offer poor scalability, in turn hindering commercialization.This study introduces sequential thermal evaporation (STE) as a scalable method for producing narrow band gap Sn/Pb iodide PVK absorber layers for application in solar cells. The produced thin films show low doping densities, charge carrier mobilities close to 100 cm2/Vs, and charge carrier lifetimes of over 2 μs. Contrary to the established convention in solvent-based synthesis, no additives were required.An alloy of precursors (PbSnI4) was used in the deposition, lowering the number of requiredsources and increasing the production rate. Optimal annealing temperatures for FAPb0.5Sn0.5I3 and Cs0.05FA0.95Pb0.5Sn0.5I3 produced via STE were determined at 200 ◦C, showing significant improvements in charge carrier mobilities and lifetimes compared to lower annealing temperatures. The drastic increase in performance was ascribed to a recrystallization mechanism. Contrary to spin coating-based research, the introduction of cesium into the PVK structure led to reduced charge carrier mobility and lifetime. The underlying mechanism remains unclear. Addition of tin(II)fluoride (SnF2) led to reduced charge carrier mobilities and lifetimes, with slight improvement in morphology. However, its direct effects were uncertain, questioning its necessity in vacuum deposition methods for Sn-based PVK films. This works demonstrates the significant potential of STE for the production of near-intrinsic high-performance Sn/Pb iodide PVKs for solar cell applications.Chemical Engineerin
Vacuum Deposited Perovskites with a Controllable Crystal Orientation
No full textThe preferential orientation of the perovskite (PVK) is typically accomplished by manipulation of the mixed cation/halide composition of the solution used for wet processing. However, for PVKs grown by thermal evaporation, this has been rarely addressed. It is unclear how variation in crystal orientation affects the optoelectronic properties of thermally evaporated films, including the charge carrier mobility, lifetime, and trap densities. In this study, we use different intermediate annealing temperatures Tinter between two sequential evaporation cycles to control the Cs0.15FA0.85PbI2.85Br0.15 orientation of the final PVK layer. XRD and 2D-XRD measurements reveal that when using no intermediate annealing primarily the (110) orientation is obtained, while when using Tinter = 100 °C a nearly isotropic orientation is found. Most interestingly for Tinter > 130 °C a highly oriented PVK (100) is formed. We found that although bulk electronic properties like photoconductivity are independent of the preferential orientation, surface related properties differ substantially. The highly oriented PVK (100) exhibits improved photoluminescence in terms of yield and lifetime. In addition, high spatial resolution mappings of the contact potential difference (CPD) as measured by KPFM for the highly oriented PVK show a more homogeneous surface potential distribution than those of the nonoriented PVK. These observations suggest that a highly oriented growth of thermally evaporated PVK is preferred to improve the charge extraction at the device level.Photovoltaic Materials and DevicesTeam Peyman TaheriChemE/Opto-electronic MaterialsTeam Arjan MolChemE/O&O groe
DIMUON PRODUCTION BY NEUTRINOS IN THE FERMILAB 15-FT. BUBBLE CHAMBER AT THE TEVATRON
No full textThe Fermilab 15-ft bubble chamber has been exposed to a quadrupole triplet neutrino beam produced at the Tevatron. The ratio of to in the beam is approximately 2.5. The mean event energy for -induced charged-current events is 150 GeV, and for -induced charged-current events it is 110 GeV. A total of 64 dimuon candidates (1+, 52 -+ and -, and 11 --) is observed in the data sample of approximately 13 300 charged-current events. The number and properties of the -- and + candidates are consistent with their being produced by background processes, the important sources being and K decay and punchthrough. The 90%-C.L. upper limit for --/- for muon momenta above 4 GeV/c is 1.2×10-3, and for momenta above 9 GeV/c this limit is 1.1×10-3. The opposite-sign-dimuono single-muon ratio is (0.62±0.13)% for muon momenta above 4 GeV/c. There are eight neutral strange particles in the opposite-sign sample, leading to a rate per dimuon event of 0.65±0.29. The opposite-sign-dimuon sample is consistent with the hypothesis of charm production and decay. © 1990 The American Physical Society.079 auteursSCOPUS: ar.jinfo:eu-repo/semantics/publishe
COHERENT PRODUCTION OF pi+ pi- MESONS BY CHARGED CURRENT INTERACTIONS OF NEUTRINOS AND ANTI-NEUTRINOS ON NEON NUCLEI AT THE TEVATRON
No full textCoherent single-pion production on neon nuclei is studied using the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mixture and exposed to the Tevatron neutrino beam. In the neutrino energy range 40ε300 GeV, the net signal is 20±6 events, giving a corrected rate per charged-current event of (0.26±0.10)%. The cross section and kinematic distributions agree with the predictions of a model based on partial conservation of axial-vector current and meson dominance. © 1989 The American Physical Society.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Centrality dependence of charged-neutral particle fluctuations in 158A (GeVPb)-Pb-208+Pb-208 collisions
No full textResults on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158A GeV/c Pb+Pb collisions are presented for varying centralities. The charged versus neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set
Delta(++) production in 158 A GeV Pb-208+Pb-208 interactions at the CERN SPS
No full textThe Delta(++)-resonance production in central 158 A GeV Pb-208 + Pb-208 collisions at the CERN SPS has been studied. The Delta(++) production was estimated from the invariant mass spectrum of p pi(+)-pairs by subtracting a mixed event background. The measured Delta(++) abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium. (C) 2000 Elsevier Science B.V. All rights reserved
Centrality and transverse momentum dependence of collective flow in 158 A GeV Pb+Pb collisions measured via inclusive photons
No full textDirected and elliptic flow of inclusive photons near mid-rapidity in 158 A GeV Pb + Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of p(T) and rapidity over 0. 18 <p(T) <1.5 GeV/c and 2.3 <y <2.9. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlations and shown to give similar results. A small directed flow component is observed. Both the directed and elliptic flow strengths increase with p(T). The photon flow results are used to estimate the corresponding neutral pion flow. (c) 2005 Elsevier B.V. All rights reserved
Localized charged-neutral fluctuations in 158A GeVPb plus Pb collisions
No full textLocalized fluctuations in the multiplicity of charged particles and photons produced in central 158A GeV/c Pb+Pb collisions are studied. The charged versus neutral correlations in common eta-phi phase space regions of varying azimuthal size are analyzed by two different methods. The analysis provides a model-independent demonstration of nonstatistical fluctuations in both charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charge-neutral fluctuations are observed, contrary to expectations for the production of a disoriented chiral condensate. The result is not explained by the widely used VENUS model
Observation of direct photons in central 158A GeV Pb-208+Pb-208 collisions
No full textA measurement of direct photon production in Pb-208 + Pb-208 collisions at 158A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5 1.5 GeV/c. The result constitutes the first observation of direct photons in ultrarelativistic heavy-ion collisions. It could be significant for diagnosis;of quark-gluon-plasma formation
First evidence of directed flow at 158 A GeV Pb+Pb collisions in WA98 experiment
No full textThe first evidence of directed flow at 158 A GeV Pb + Pb collisions is observed using the Plastic Ball detector in WA98 experiment. The azimuthal angle of the total transverse energy, Phi(o), is determined for each event using the observed protons in the Plastic Ball. A clear azimuthal asymmetry of fragments is observed with respect to Phi(o). The degree of azimuthal asymmetry is found to be largest in mid-central collisions, which is consistent with the picture of the collective flow. The p(t) spectra of particles measured in the mid-rapidity spectrometer has been studied in conjunction with the Plastic Ball, and different p(t) slopes with respect to Phi(o) for proton and pi(+) are observed
