Effect of the magnetic order on the room-temperature band-gap of Mn-doped ZnO thin films

Author name used in this publication: Ruotolo A.2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

High-Temperature Stable Operation of Nanoribbon Field-Effect Transistors

We experimentally demonstrated that nanoribbon field-effect transistors can be used for stable high-temperature applications. The on-current level of the nanoribbon FETs decreases at elevated temperatures due to the degradation of the electron mobility. We propose two methods of compensating for the variation of the current level with the temperature in the range of 25–150°C, involving the application of a suitable (1) positive or (2) negative substrate bias. These two methods were compared by two-dimensional numerical simulations. Although both approaches show constant on-state current saturation characteristics over the proposed temperature range, the latter shows an improvement in the off-state control of up to five orders of magnitude (−5.2 × 10−6)

Ferromagnetism in Ti-doped ZnO thin films

2014-2015 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Enhanced Raman scattering from vertical silicon nanowires array

2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Effect of PTB7 Properties on the Performance of PTB7:PC71BM Solar Cells

The effect of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) properties on the optical properties, charge transport and photovoltaic performance of PTB7:[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) blend films is investigated. We found that the variations in the molecular weight (Mw) and polydispersity index (PDI) of PTB7 mainly affect the phase separation and charge transport (hole mobility) in the blend films. The optical properties are also affected, but the increase in the extinction coefficient does not necessarily imply increased power conversion efficiency. The obtained power conversion efficiency for optimized thickness varied from 4.8% to 7.8% depending on the properties of PTB7. The wide range of obtained power conversion efficiencies illustrates the importance of optimizing the Mw and PDI to optimize bulk heterojunction morphology and achieve high performance solar cells.Department of Electronic and Information Engineerin

Accurate determination of the index of refraction of polymer blend films by spectroscopic ellipsometry

To model the performance of a bulk-heterojunction solar cell, it is necessary to obtain information about the index of refraction of the blend layer, which is typically determined by spectroscopic ellipsometry measurements. The optical functions of poly(3-hexylthiophene)-[6,6]-phenyl C 61-butyric acid methyl ester (P3HT-PCBM) blend films have been extensively studied. However, there is a large variation of the reported optical functions in the literature. Because of this fact, as well as the widespread use of P3HT-PCBM films in organic photovoltaics, we have selected this material system as an example and performed a detailed analysis of spectroscopic ellipsometry data. We illustrate the occurrence of multiple solutions and the importance of a dedicated methodology to reach a satisfactory unique solution. The proposed methodology involves the following steps: (1) multisample analysis; (2) independent thickness and surface characterization; (3) use of the adequate optical description of substrate; (4) thickness estimation from transparent range using Cauchy model; (5) fitting n and k in the entire range with fixed thickness; verify result is physically meaningful; (6) optimization of the parameters to be fitted; (7) repeating steps 5 and 6 with and without EMA layer to account for the surface roughness; (8) finally, and only if no satisfactory fit could be obtained from previous steps, attempts to introduce anisotropy, graded layers, or other nonideal models should follow. © 2010 American Chemical Society.link_to_subscribed_fulltex

Magnetism as a tool for band-gap narrowing of zinc oxide films prepared by sol–gel method

202308 bcvcAccepted ManuscriptRGCOthersThe National Science Foundation of ChinaPublishe