Heterojunction Hybrid Devices from Vapor Phase Grown MoS2_{2}

We investigate a vertically-stacked hybrid photodiode consisting of a thin n-type molybdenum disulfide (MoS$_{2}$) layer transferred onto p-type silicon. The fabrication is scalable as the MoS$_{2}$ is grown by a controlled and tunable vapor phase sulfurization process. The obtained large-scale p-n heterojunction diodes exhibit notable photoconductivity which can be tuned by modifying the thickness of the MoS$_{2}$ layer. The diodes have a broad spectral response due to direct and indirect band transitions of the nanoscale MoS$_{2}$. Further, we observe a blue-shift of the spectral response into the visible range. The results are a significant step towards scalable fabrication of vertical devices from two-dimensional materials and constitute a new paradigm for materials engineering.Comment: 23 pages with 4 figures. This article has been published in Scientific Reports. (26 June 2014, doi:10.1038/srep05458

Studies on the encapsulation of various anions in different fullerenes using density functional theory calculations and born–oppenheimer molecular dynamics simulation

The density functional theory (DFT)-based Becke’s three parameter hybrid exchange functional and Lee–Yang–Parr correlation functional (B3LYP) calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations have been performed to understand the stability of different anions inside fullerenes of various sizes. As expected, the stability of anion inside the fullerene depends on its size as well as on the size of the fullerene. Results show that the encapsulation of anions in larger fullerenes (smaller fullerene) is energetically favorable (not favorable). The minimum size of the fullerene required to encapsulate F– is equal to C32. It is found from the results that C60 can accommodate F–, Cl–, Br–, OH–, and CN–. The electron density topology analysis using atoms in molecule (AIM) approach vividly delineates the interaction between fullerene and anion. Although F–@C30 is energetically not favorable, the BOMD results reveal that the anion fluctuates around the center of the cage. The anion does not exhibit any tendency to escape from the cage

Density functional theory calculations on the diamond nitrogen-vacancy center

Godkänd; 2015; Bibliografisk uppgift: Supercell and slab calculations with Vasp; 20150219 (roblof

Natural Compound Modulates the Cervical Cancer Microenvironment—A Pharmacophore Guided Molecular Modelling Approaches

Cervical cancer is regarded as one of the major burdens noticed in women next to breast cancer. Although, human papilloma viruses (HPVs) are regarded as the principal causative agents, they require certain other factors such as oestrogen hormone to induce cervical cancer. Aromatase is an enzyme that converts androgens into oestrogens and hindering this enzyme could subsequently hamper the formation of oestrogen thereby alleviating the disease. Accordingly, in the current investigation, a structure based pharmacophore was generated considering two proteins bearing the Protein Data Bank (PDB) codes 3EQM (pharm 1) and 3S7S (pharm 2), respectively. The two models were employed as the 3D query to screen the in-house built natural compounds database. The obtained 51 compounds were escalated to molecular docking studies to decipher on the binding affinities and to predict the quintessential binding modes which were affirmed by molecular dynamics (MD) simulations. The compound has induced dose-dependent down regulation of PP2B, Nitric oxide synthase-2 (NOS2), and Interleukin 6 (IL-6) genes in the HeLa cells and has modulated the expression of apoptotic genes such as Bax, Bcl2, and caspases-3 at different concentrations. These results guide us to comprehend that the identified aromatase inhibitor was effective against the cervical cancer cells and additionally could server as scaffolds in designing new drugs

Protecting group/halogen effect of N-glycosylamines on the self assembly of organogelator

A series of N-glycosylamine based organogelators were synthesised from three different 4,6-O-protected saccharides. All these compounds were characterized using different spectral techniques. The effect of substituents present in the N-glycosylamines on gelation was studied from NMR and computation. Among the eighteen different gelators studied, 3b, bearing fluorine as a substituent, was observed to gelate at very low concentrations (CGC: 1%). Further, it is revealed that dipole–dipole interactions play an important role in the case of N-glycosylamine-based gelators. The presence of π–π stacking and H-bonding, as inferred from the reported X-ray diffraction data, are responsible for the gelation. Various possible modes of interaction are identified from computational studies. The gelation properties of these compounds were studied with regard to their molecular structure by scanning electron microscopy, differential scanning calorimetry, FT-IR and NMR studies

Improving the efficiency of organic solar cells with graphene transparent electrode and light management: a simulation study

In this work, we provide fabrication guidelines to obtain high efficient organic solar cells exploiting graphene as substitute to ITO transparent electrode. The design is performed through multi-scale simulations, ranging from the atomistic level by means of ab-initio calculations of the contact, up to the device level through drift-diffusion models, including also excitonic transport. Optical modelling has also been performed in order to investigate enhancement of the solar cell efficiency through proper contact patterning. We will show that an efficiency improvement in excess of 30% with respect to the reference cell is achievable

Simulation of Organic Solar Cell with Graphene Transparent Electrode

We present a simulation study of the performance of organic solar cell (OSC) exploiting graphene as transparent electrode. The approach is based on a multi-scale/multi-physics simulation framework, which is able to provide relevant information regarding the design guidelines of efficient OSC

Can graphene outperform indium tin oxide as transparent electrode in organic solar cells?

http://www.gianlucafiori.org/articles/paletti_2Dmaterials.pdf Graphene holds promises as a transparent electrode in flexible solar cells due to its high mobility and transparency. However, the experimental power conversion efficiency of cells with graphene electrode is still small (<7%). In this paper, we evaluate possible engineering options to improve the power conversion efficiency, by means of multi-scale simulation approach including ab-initio simulations of graphene contacts to improve electrode workfunction and conductance, electromagnetic simulations to improve light management, and electrical simulations of complete cells. We find that the combined effect of using a transparent electrode of graphene with a few monolayers of MoO3 on top to optimize work function and resistivity, and of applying optimized grating to the graphene electrode, can increase power efficiency by up to 29%–47%, with respect to the ITO benchmark, depending on the material used for the hole transport layer (P3HT,PTB7, and Perovskite)