Spectroscopy of Charge Carriers at Ionic Liquid/Semiconductor Interfaces

The interface of semiconductors plays an important role in all semiconductor devices - often defining the device's properties. Ionic liquids are typically employed as gating dielectrics to achieve high charge densities at semiconductor surfaces. Such ionic liquid/semiconductor interfaces are usually studied using electrical transport techniques, which often have the drawback of requiring modeling to achieve an understanding of the species involved in the devices at the ionic liquid/semiconductor interfaces. Through the use of infra-red and optical spectroscopy this work seeks to uncover the nature of charge carriers surface of both organic semiconductors, specifically rubrene, and two dimensional semiconductors, specifically monolayer MoS2, and how these charges interact in the presence of mobile ions. I show that for rubrene infra-red spectroscopy reveals with the formation of an ionic liquid/rubrene interface the rubrene surface becomes intrinsically hole doped. Additionally, that when rubrene is gated the ionic liquid to achieve high charge densities in rubrene there is a saturation of the conductive species resulting in a lowering of hole mobility. In the case of monolayer MoS2 photoluminescence spectroscopy shows that forming the ionic liquid/MoS2 interface results in mobile ions screen the charged defects in the MoS2 increasing the photoluminescence intensity

Lead halide perovskites: Crystal-liquid duality, phonon glass electron crystals, and large polaron formation

Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids. This “crystal-liquid” duality implies that lead halide perovskites belong to phonon glass electron crystals, a class of materials believed to make the most efficient thermoelectrics. We show that the crystal-liquid duality and the resulting dielectric response are responsible for large polaron formation and screening of charge carriers, leading to defect tolerance, moderate charge carrier mobility, and radiative recombination properties. Large polaron formation, along with the phonon glass character, may also explain the marked reduction in hot carrier cooling rates in these materials

ECONOMIC IMPACT OF GRAPEVINE LEAFROLL DISEASE ON VITIS VINIFERA CV. CABERNET FRANC IN FINGER LAKES VINEYARDS OF NEW YORK

WP 2011-14 June 2011Leafroll disease is one of the most important virus diseases of grapevines worldwide. It reduces yields, delays fruit ripening, reduces soluble solids and increases titratable acidity in fruit juice. This study uses a Net Present Value (NPV) approach over a 25-year lifespan of a vineyard to examine the economic impact of grapevine leafroll disease (GLD) on Vitis vinifera cv. Cabernet franc in Finger Lakes vineyards of New York. It identifies optimal disease control options under several scenarios of disease prevalence, yield reduction, and fruit quality effects. The estimated economic impact of GLD ranges from about 25,000 (for a 30&percent; yield reduction and no grape quality penalty) to 40,000 (for a 50&percent; yield reduction and a 10&percent; penalty for poor fruit quality) per hectare in the absence of any control measure. The per-hectare impact of GLD can be substantially reduced to $3,000-$23,000 through roguing if levels of disease prevalence are moderate (1&percent; to 25&percent;). With disease prevalence levels higher than 25&percent;, replacing the entire vineyard is the optimal response, yielding economic losses of about $25,000 per hectare. Furthermore, the use of vines derived from certified, virus-tested stocks in replant sites is predicted to keep the costs associated with GLD infection to about$1,800 per hectare. Also, ‘no intervention’ appears to be the best management strategy when (1) infection levels are high (>25&percent;), yield reduction is moderate (<30&percent;) and no price penalty is enforced, or (2) GLD is transmitted through vectors after year 19. These findings are valuable to construct integrated decision matrices for vineyard managers to devise profit-maximizing disease control strategies and to create incentives for extended uses of clean, virus-tested planting material

Spectrally-selective Time-resolved Emission through Fourier-filtering (STEF)

In this manuscript we demonstrate that directing the emitted photon stream from a fluorescent sample through a fixed path-length imbalanced Mach-Zehnder interferometer allows us to separate and resolve the dynamics of different emitters without the use of filtering optics. Our method, Spectrallyselective Time-resolved Emission through Fourier-filtering (STEF) takes advantage of a careful selection of interferometer position where one signal can be canceled (or enhanced) due to its unique spectral characteristics. STEF is straightforward to implement and provides a complementary approach to separate spectrally overlapped signals based on their coherence length and carrier frequency. We also discuss how one can implement STEF with an imperfect Mach-Zehnder interferometer, increasing the utility of this method, and demonstrate how Mach-Zehnder filtering can be used to image fluorophores in biologically relevant samples

Economic Analysis of the Financial Impact of the Grape Leafroll Virus (GLRV) in the Finger Lakes Region of New York

E.B. 2010-15Leafroll is one of the most important virus diseases of grapevines worldwide, reducing the yield and quality of grapes. The present study is aimed at quantifying the cost impact of the grape leafroll virus (GLRV) and identifying the best disease management options under several scenarios of reduced yield and quality. The costs associated with the absence of response to the GLRV ranged from $9,695 (for a 30$16,014 per acre (case of 50% reduction in yield and 10% penalty). This cost impact was lowered to a range of $547-$9,336 (for GLRV incidences 1- 27%) through roguing1 and $9,384 through vineyard replacement (GLRV incidences above 27$740. Roguing turned out to be the appropriate management method if the GLRV incidence is below 27%. Above that level, replacement was found to be the best option. However, there were two cases where ‘no intervention’ was the best management practice. The first is the case where yield reduction is less than 30%, GLRV incidences greater than 27% and no price penalty is enforced. The second is a situation of a vector transmitted infection happening beyond year 19. Beyond that age, roguing did not have a positive impact on the Net Present Value (NPV), suggesting no intervention in that case as well

Decay Associated Fourier Spectroscopy: Visible to Shortwave Infrared Time-Resolved Photoluminescence Spectra

We describe and implement an interferometric approach to decay associated photoluminescence spectroscopy, which we term decay associated Fourier spectroscopy (DAFS). In DAFS, the emitted photon stream from a substrate passes through a variable path length Mach-Zehnder interferometer prior to detection and timing. The interferometer encodes spectral information in the intensity measured at each detector enabling simultaneous spectral and temporal resolution. We detail several advantages of DAFS, including wavelength-range insensitivity, drift-noise cancellation, and optical mode retention. DAFS allows us to direct the photon stream into an optical fiber, enabling the implementation of superconducting nanowire single photon detectors for energy-resolved spectroscopy in the shortwave infrared spectral window (λ=1-2 μm). We demonstrate the broad applicability of DAFS, in both the visible and shortwave infrared, using two Förster resonance energy transfer pairs: a pair operating with conventional visible wavelengths and a pair showing concurrent acquisition in the visible and the shortwave infrared regime