Thin Film PbS Quantum Dot Solar Cells

The charge carrier kinetics of P and N type Lead sulfide quantum dots were examined to determine metrics for both hole and electron transport during solar cell operation. This was achieved by using a dual illumination scheme to excite the solar cell through front and back transparent contacts. By changing the illumination direction, the distances hole and electrons travel will also be switched. This allows us to measure the carrier kinetics of the farthest moving charge carrier during solar cell operation. Using JV, IPCE, and current decay measurements, this study found that hole and electron transport in N type PbS is symmetrical and in P type PbS, electron transport suffers compared to hole transport. With the addition of a P/N junction between the two quantum dot layers, the transit times for both holes and electrons decreased significantly with large improvements in electron transport in P type PbS. Tamm surface plasmons were also investigated to determine their effect on the optoelectronic properties of PbS quantum dot solar cells. Tamm surface plasmons are created when a Bragg mirror is in conjunction with a thin metal film. Strong plasmonic resonances occur in the metal film for photons with the same wavelength as the Bragg mirror. When put in conjunction with a PbS solar cell, the plasmonic film enhanced the light absorption of the device leading to more photon absorption and charge generation, improving the efficiency of the PbS quantum dot solar cell. Light absorption was improved through near and far field plasmonic effects. Near field effects coupled light to the gold film greatly increasing the optical cross section of PbS near the thin film for photons near the Bragg wavelength of the Tamm plasmon substrate. Far field reflectance effects also enhanced the photon optical pathway to allow for a higher probability of light absorption. Different wavelength of light can be targeted by the Tamm surface plasmon effect by changing the dielectric layer thicknesses of the underlying Bragg mirror. The body of this work can be applied to other solar cell types to acquire qualitative information on hole and electron transport to improve the design of devices. Tamm surface plasmons are an understudied top in the field of plasmonic assisted solar cell design and this paper can act as a stepping stone for future research

The Story of the Dublin Institute of Technology

The Dublin Institute of Technology (DIT) was statutorily established as an autonomous institution on 1 January 1993, under the Dublin Instute of Technology Act (1992). It was constituted from the six higher education colleges of the City of Dublin Vocational Education Committee. This book describes the evolution and accomplishments of the Institute from its beginnings 113 years ago, and includes its rapid academic developments over the past thirty years. The DIT is now a multi-level higher education institution with the largest enrolment of all the higher education institutions in the state - about 22,000 (10,500 full-time students, 4,000 apprentices and some 7,500 other part-time students).https://arrow.tudublin.ie/ditpress/1000/thumbnail.jp

Hand classification of fMRI ICA noise components

We present a practical "how-to" guide to help determine whether single-subject fMRI independent components (ICs) characterise structured noise or not. Manual identification of signal and noise after ICA decomposition is required for efficient data denoising: to train supervised algorithms, to check the results of unsupervised ones or to manually clean the data. In this paper we describe the main spatial and temporal features of ICs and provide general guidelines on how to evaluate these. Examples of signal and noise components are provided from a wide range of datasets (3T data, including examples from the UK Biobank and the Human Connectome Project, and 7T data), together with practical guidelines for their identification. Finally, we discuss how the data quality, data type and preprocessing can influence the characteristics of the ICs and present examples of particularly challenging datasets

On the creation of thermal equations of state for use in Dioptas

Dioptas is a widely used software package for integrating and analysing 2-dimensional diffraction images. To help interpret the integrated diffraction profiles it produces, Dioptas users can input files that parameterise a material's thermal equation of state (EoS), enabling the positions of the Bragg peaks from that material to be calculated as a function of pressure and temperature. However, care is needed to ensure that these input files correctly describe the thermal EoS of interest. Here we describe the thermal EoS model used by Dioptas and show how existing thermal EoS should be reparameterised so as to be used correctly in Dioptas. Input EoS files suitable for use with Dioptas are provided for the following commonly-used pressure calibrants and pressure transmitting media: Al, Au, Cu, Mo, Nb, Pt, Ta, hcp-Fe, MgO, NaCl-B1, NaCl-B2, KCl-B2, and Ne.</p

Discrete Gravitational Dimensions

We study the physics of a single discrete gravitational extra dimension using the effective field theory for massive gravitons. We first consider a minimal discretization with 4D gravitons on the sites and nearest neighbor hopping terms. At the linear level, 5D continuum physics is recovered correctly, but at the non-linear level the theory becomes highly non-local in the discrete dimension. There is a peculiar UV/IR connection, where the scale of strong interactions at high energies is related to the radius of the dimension. These new effects formally vanish in the limit of zero lattice spacing, but do not do so quickly enough to reproduce the continuum physics consistently in an effective field theory up to the 5D Planck scale. Nevertheless, this model does make sense as an effective theory up to energies parametrically higher than the compactification scale. In order to have a discrete theory that appears local in the continuum limit, the lattice action must have interactions between distant sites. We speculate on the relevance of these observations to the construction of finite discrete theories of gravity in four dimensions.Comment: 5 pages, 4 diagrams. Important typos in some equations corrected; conclusion s unchange

Confinement and Strings in MQCD

We study aspects of confinement in the M theory fivebrane version of QCD (MQCD). We show heavy quarks are confined in hadrons (which take the form of membrane-fivebrane bound states) for N=1 and softly broken N=2 SU(Nc) MQCD. We explore and clarify the transition from the exotic physics of the latter to the standard physics of the former. In particular, the many strings and quark-antiquark mesons found in N=2 field theory by Douglas and Shenker are reproduced. It is seen that in the N=1 limit all but one such meson disappears while all of the strings survive. The strings of softly broken N=2, N=1, and even non-supersymmetric SU(Nc) MQCD have a common ratio for their tensions as a function of the amount of flux they carry. We also comment on the almost BPS properties of the Douglas-Shenker strings and discuss the brane picture for monopole confinement on N=2 QCD Higgs branches.Comment: 39 pages, 17 figures, uses harvma

Effective Field Theory for Massive Gravitons and Gravity in Theory Space

We introduce a technique for restoring general coordinate invariance into theories where it is explicitly broken. This is the analog for gravity of the Callan-Coleman-Wess-Zumino formalism for gauge theories. We use this to elucidate the properties of interacting massless and massive gravitons. For a single graviton with a Planck scale Mpl and a mass mg, we find that there is a sensible effective field theory which is valid up to a high-energy cutoff Lambda parametrically above mg. Our methods allow for a transparent understanding of the many peculiarities associated with massive gravitons, among them the need for the Fierz-Pauli form of the Lagrangian, the presence or absence of the van Dam-Veltman-Zakharov discontinuity in general backgrounds, and the onset of non-linear effects and the breakdown of the effective theory at large distances from heavy sources. The natural sizes of all non-linear corrections beyond the Fierz-Pauli term are easily determined. The cutoff scales as Lambda ~ (mg^4 Mpl)^(1/5) for the Fierz-Pauli theory, but can be raised to Lambda ~ (mg^2 Mpl)^(1/3) in certain non-linear extensions. Having established that these models make sense as effective theories, there are a number of new avenues for exploration, including model building with gravity in theory space and constructing gravitational dimensions.Comment: 22 pages, 7 diagrams; references and some clarifying comments added, typos correcte

Low-noise RF-amplifier-free slab-coupled optical waveguide coupled optoelectronic oscillators: physics and operation

We demonstrate a 10-GHz RF-amplifier-free slab-coupled optical waveguide coupled optoelectronic oscillator (SCOW-COEO) system operating with low phase-noise (-115 dBc/Hz at 1 kHz offset) and large sidemode suppression (70 dB measurement-limited). The optical pulses generated by the SCOW-COEO exhibit 26.8-ps pulse width (post compression) with a corresponding spectral bandwidth of 0.25 nm (1.8X transform-limited). We also investigate the mechanisms that limit the performance of the COEO. Our measurements indicate that degradation in the quality factor (Q) of the optical cavity significantly impacts COEO phase-noise through increases in the optical amplifier relative intensity noise (RIN)