Three driving forces control the energy level alignment between transition-metal oxides and organic materials: the chemical interaction between the two materials, the organic electronegativity and the possible space charge layer formed in the oxide. This is illustrated in this letter by analyzing experimentally and theoretically a paradigmatic case, the TiO2(110) / TCNQ interface: due to the chemical interaction between the two materials, the organic electron affinity level is located below the Fermi energy of the n-doped TiO2. Then, one electron is transferred from the oxide to this level and a space charge layer is developed in the oxide inducing an important increase in the interface dipole and in the oxide work function.
Excitons are widely found in semiconductors. In contrast to inorganic-based semiconductors, where the presence of excitons may need special morphonology, like low-dimensional layer structure, the excitons prevailingly exist in molecular organic semiconductors in a three-dimension solid state. The excitons can undergo a charging process to yield another kind of quasiparticles originating from the coupling of excitons and free charges. Herein, we investigated the interaction between excitons and free charges in a representative arylamine-derivative organic semiconductor(NPB), by the time-of-flig…
Our research shows that commercially available graphene on quartz modified with rhenium oxide meets the requirements for its use as a conductive and transparent anode in optoelectronic devices. The cluster growth of rhenium oxide enables an increase in the work function of graphene by 1.3 eV up to 5.2 eV, which guarantees an appropriate adjustment to the energy levels of the organic semiconductors used in OLED devices.
The origin of negative charging in amorphous Al$_2$O$_3$ films: The role of native defects
通过各种沉积技术生长的无定形氧化铝Al $_2$ O $_3$（a-Al $_2$ O $_3$）层含有显著密度的负电荷。尽管有一些实验和理论研究，这些电荷的起源仍然不清楚。我们报告了广泛的密度泛函理论（DFT）计算结果的原生缺陷- O和Al空位和晶体，以及H间隙中心-在两个结晶$α$ -Al $_2$ O $_3$和α-Al $_2$ O $_3$在不同的电荷状态。结果表明，a-Al $_2$ O $_3$薄膜的充电过程和负电荷陷阱的能量分布都与薄膜的电荷分布有关[M. B. Zahid等人，IEEE Trans. Electron Devices 57，2907（2010）]可以理解为假设所制备的样品中带负电荷的O $_{\textrm{i}}$和V $_{\textrm{Al}}$缺陷几乎被带正电荷的H $_{\textrm{i}}$、V $_{\textrm{O}}$和Al $_{\textrm{i}}$缺陷补偿。电子注入后，带隙中Al $_{\textrm{i}}$、V $_{\textrm{O}}$或H $_{\textrm{i}}$的状态被电子占据，样品带负电。从这些态到氧化物导带的光学激发能与穷举光电子减布居谱（EPDS）测量结果一致[M. B. Zahid等人，IEEE Trans. Electron Devices 57，2907（2010）]。对a-Al $_…
The performance of solution-processed organic light emitting diodes (OLEDs) is often limited by non-uniform contacts. In this work, we introduce Ni-containing solution-processed metal oxide (MO) interfacial layers inserted between indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to improve the bottom electrode contact for OLEDs using the poly(p-phenylene vinylene) (PPV) derivative Super-Yellow (SY) as an emission layer. For ITO/Ni-containing MO/PEDOT:PSS bottom electrode structures we show enhanced wetting properties that result in an improved OLE…
Organic functionalization of graphene is successfully performed via 1,3-dipolar cycloaddition of azomethine ylide in the liquid phase. The comparison between 1-methyl-2-pyrrolidinone and N,N-dimethylformamide as dispersant solvents, and between sonication and homogenization as dispersion techniques, proves N,N-dimethylformamide and homogenization as the most effective choice. The functionalization of graphene nanosheets and reduced graphene oxide is confirmed using different techniques. Among them, energy-dispersive X-ray spectroscopy allows to map the pyrrolidine ring of the azomethine ylide …
Mobile Small Polarons Explain Conductivity in Lithium Titanium Oxide Battery Electrodes
锂钛氧化物Li $_4$ Ti $_5$ O $_{12}$（LTO）是一种有趣的阳极材料，由于其在电池充电（放电）期间显著的相稳定性，因此特别有希望成为长寿命电池。然而，它的使用受到其低固有电子电导率的限制。引入氧空位可以是克服该缺点的一种方法，可能通过改变载流子传输机制。我们使用Hubbard修正的密度泛函理论（DFT+U）表明，极化子状态结合可能的跳跃机制可以发挥至关重要的作用，在实验观察到的电子电导率的增加。为了衡量极化子电荷迁移率，我们计算了不同的本地化模式的相对稳定性和估计极化子跳跃势垒高度。有了这个，我们最终展示了缺陷工程如何确实可以提高LTO的电子电导率的水平，其离子电导率，从而解释了第一个实验结果减少LTO。
Enhanced Tantalum Superconducting Resonator Performance via All-Surface Organic Monolayer Passivation
Technical University of Munich（慕尼黑工业大学）；Indian Institute of Technology Roorkee（罗克基印度理工学院）；Fraunhofer Institute for Electronic Microsystems and Solid State Technologies (EMFT)（弗劳恩霍夫电子微系统和固态技术研究所）
We study the behavior of hydrated graphite oxide (GO) at high temperatures using thermally accelerated molecular dynamics simulations based on ab initio density functional theory. Our results suggest that GO, a viable candidate for water treatment and desalination membranes, is more heat resilient than currently used organic materials. The system we consider to represent important aspects of thermal processes in highly disordered GO is a hydrated GO bilayer in vacuum. Our study provides microscopic insight into reactions involving water and functional epoxy-O and OH-groups bonded to graphene l…
The ideal band gap for a photovoltaic active layer for the solar spectrum is around 1.3 eV. However oxides with such values are rare. One of the most studied oxides to date as a photovoltaic active layer is the cuprous oxide Cu2O. Its band gap is around 2.1 eV and is therefore not ideal for the solar spectrum. Power Conversion Efficiency generally do not exceed 4%. In this paper we propose to study an emerging type of solar cell that is based on ferroelectricity. In this type of solar cell, a p-n junction is not necessarily required, unlike conventional solar cells. Interesting conversion effi…
Engineering of SnO2-Graphene Oxide Nano-Heterojunctions for Selective Room-temperature Chemical Sensing and Optoelectronic Devices
Università degli Studi di Milano（米兰大学）；Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM)（意大利国家材料科学与技术大学联盟）；The Australian National University（澳大利亚国立大学）
