Reduced Graphene Oxide-Modified Tin Oxide Thin Films for Energy and Environmental Applications

Metal halide perovskite solar cells (PSCs) have attracted tremendous attention because of their rapid development. To enhance the power conversion efficiency (PCE) of PSCs, significant research efforts have focused on the optimization of electron transport layer (ETL). SnO2 has been extensively used as ETL due to its excellent electron transport properties. The optimization of the fabrication of SnO2 and passivation of the structural defects are essential to the improved performance of ETL. This thesis aims to (i) investigate the fabrication of pristine SnO2 thin film and characterize its material properties and (ii) develop a novel fabrication of reduced graphene oxide (RGO) modified SnO2 thin film as ETL and characterize its material properties. The first part was achieved by investigating the effects of UV-ozone treatment on fabrication of SnO2 thin films as well as the effects of precursor concentration and heating temperature on the resultant properties of the SnO2 thin films. The results showed that UV-ozone pretreatment is essential for depositing a continuous SnO2 thin film. A high precursor concentration resulted in low roughness and high n-type defects in SnO2 thin film, which would decrease the electrical conductivity while a high temperature of heat treatment resulted in increased crystallinity and a decrease in oxygen vacancies and residual Cl. The second part was achieved by investigating the effects of (i) preparation time of the RGO-SnO2 precursor and (ii) the concentration of RGO on the properties of RGO-SnO2 thin films. The RGO-SnO2 thin film was successfully fabricated by spin coating a precursor solution of SnCl2 in ethanol (95%) mixed with graphene oxide (GO) followed by heating at low temperatures. By conducting RGO modification, RGO-SnO2 thin films with high crystallinity and low oxygen vacancy contents were achieved resulting in a high electrical conductivity. The study showed that 3 h of preparation time for the precursor and addition amounts of 2.62 wt% RGO would result in the best properties of the RGO-SnO2 thin films. This ETL has a surface roughness Ra of <20 nm, good band alignment with perovskite materials (CBM <3.9 eV), and electrical conductivity of 30 x 10-5 S/m, which can enable its use in high-performance PSCs

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

Focussed Review of Utilization of Graphene-Based Materials in Electron Transport Layer in Halide Perovskite Solar Cells: Materials-Based Issues

The present work applies a focal point of materials-related issues to review the major case studies of electron transport layers (ETLs) of metal halide perovskite solar cells (PSCs) that contain graphene-based materials (GBMs), including graphene (GR), graphene oxide (GO), reduced graphene oxide (RGO), and graphene quantum dots (GQDs). The coverage includes the principal components of ETLs, which are compact and mesoporous TiO2, SnO2, ZnO and the fullerene derivative PCBM. Basic considerations of solar cell design are provided and the effects of the different ETL materials on the power conversion efficiency (PCE) have been surveyed. The strategy of adding GBMs is based on a range of phenomenological outcomes, including enhanced electron transport, enhanced current density-voltage (J-V) characteristics and parameters, potential for band gap (Eg) tuning, and enhanced device stability (chemical and environmental). These characteristics are made complicated by the variable effects of GBM size, amount, morphology, and distribution on the nanostructure, the resultant performance, and the associated effects on the potential for charge recombination. A further complication is the uncertain nature of the interfaces between the ETL and perovskite as well as between phases within the ETL

Study on evaluation of lightscape under forests in urban parks

Abstract In order to explore the evaluation system of lights cape under forest in the urban park, an evaluation system of lights cape under forest in the urban park was constructed, which was composed of physical factors, psychological factors and spatial factors and the corresponding 12 indexes affecting the lights cape based on Grey Statistical Theory and Analytic Hierarchy Process. The results show that: 1) Psychological and physical factors are the dominant influencing indexes in the evaluation system, and the weight accounting of these factors is more than 70%. 2) The total weight of illumination uniformity is higher than other evaluation indexes. 3)The important indicators and sub-important indicators that affect the evaluation of lights cape under forest in the urban park are as follows: illumination Uniformity, satisfaction of lights cape, audio-visual coordination, sky View Factor, daylight factor under forests, perception of privacy, perception of security and clear bole height, etc. The evaluation system is expected to provide theoretical basis and effective methods for the future study in urban light environment.</jats:p