二萘嵌苯二酰亚胺衍生物的半导体性质

应用密度泛函理论研究了四种二萘嵌苯二酰亚胺(PDI)(N,N'-二萘嵌苯-3,4,9,10-四羧酸二酰亚胺(1), N,N'-二(3-氯苯甲基)二萘嵌苯-3,4,9,10-四羧酸二酰亚胺(2), N,N'-二(3-氟苯甲基)二萘嵌苯-3,4,9,10-四羧酸二酰亚胺(3)和N,N'-二(3,3-二氟苯甲基)二萘嵌苯-3,4,9,10-四羧酸二酰亚胺(4))半导体材料的最高占据轨道和最低未占据轨道能量、离子化能和电子亲和能以及在电荷传导过程中的重组能. 与化合物2-4的最高占据轨道和最低未占据轨道能量变化相同, 在PDI分子外围引入氯苯甲基或氟苯甲基后导致化合物2-4的绝热电子亲和能有不同程度的增加. 应用Marcus电子传导理论, 计算了这四种半导体材料应用于有机场效应晶体管在电子传递过程中的电子耦合和迁移率. 计算结果表明:这四种化合物相对于金属金电极而言具有较小的电子注入势垒, 是优良的n型半导体材料. 计算的这四种半导体材料的电子传输迁移率分别为5.39, 0.59, 0.023和0.17 cm2·V-1·s-1. 通过研究化合物分子在还原过程中几何结构变化和在化合物3晶体中不同类型的电子传递路径, 合理地解释了化合物1-4在有机场效应晶体管电荷迁移过程中具有较高的电子迁移率.     

反胶束法合成氧化锌微晶及其荧光特性

0引言材料的结构(微结构)、尺寸和形貌等因素对其特性及其实际应用具有重要的影响。对无机材料特别是氧化物半导体进行结构控制的研究近年来引起了人们极大的关注。氧化锌作为一种宽带隙(3.2eV)半导体材料,可广泛应用于压电材料、气体传感器、橡胶添加剂和光学器件等领域,而且还因其在室温下可产生激射现象使其成为纳米光学材料研究领域中的一大热点[1￣6]。目前,除了传统的固相-气相(V S)反应外,用于氧化锌微晶的制备方法主要有共沉淀法[7]、多羟基化合物水解法[8]、有机金属气相沉积法[9￣12]和水热法[13]等。通过选择不同的制备方法和…     

多级复合半导体纳米材料的制备

金属氧化物、Ⅲ-Ⅴ、Ⅱ-Ⅵ等半导体纳米材料由于其独特的功能性质已广泛应用于光学、电子、太阳能转化、催化等领域,是当今先进材料领域的研究前沿与热点。随着科技的发展,人们对材料的高效、多功能要求已成为必然,对半导体材料发展要求亦如此。多组分复合、多层次结构协同是实现半导体纳米材料多功能化与高效化的有效途径。构筑多级结构组合纳米半导体,不但可以调控其能带结构而提高半导体材料的光电与催化性能,而且由于多级低维纳米结构聚集时形成的空间位阻效应可以有效克服纳米晶“易团聚”难题。本文提出多级结构组合纳米晶的概念、分类,结合近年来该领域的研究实践,较系统地综述了多级复合半导体纳米结构制备的最新研究进展。首先简要介绍了多级复合半导体纳米材料的概念与典型结构; 其次对典型多级复合半导体纳米材料的制备方法进行了重点评述,分别综述了液相法、气相法以及最新发展起来的静电纺丝等方法在多级结构半导体复合纳米材料制备中的应用实践。再其次,对以具有半导体特性的石墨烯及其功能化衍生物为基体的新型多级复合半导体纳米材料的制备做了综述。最后对半导体/半导体多级结构复合纳米材料的发展方向做了展望。     

一种基于ZnO纳米棒阵列膜的H_2O_2传感器

氧化锌(ZnO)是Ⅱ-Ⅵ族半导体氧化物,作为一种重要的宽禁带半导体材料,用途十分广泛.当ZnO尺寸达到纳米级别时,展现出许多优异的、特殊的性质,如无毒和非迁移性、荧光性、压电性、吸收和散射紫外线能力等,因而备受研究者的关注~([1]).     

可见光诱导Z型V2O5/g-C3N4异质结催化未活化烯烃串联反应(英文)

半导体光催化剂是一种极具前景的绿色催化剂,广泛用于污染物降解、水解制氢和有机合成等领域,有望利用太阳能来解决能源和环境问题,是当前的研究前沿和热点.然而,单组分半导体光催化剂的光生电子和空穴容易复合,导致量子效率差和光催化效率低.近年人们发现,将两种或多种催化材料结合,构建异质结光催化体系可有效促进光生电子-空穴分离.但传统的异质结体系中光生电子的还原性和光生空穴的氧化性通常在电荷转移后变弱,因此,很难同时具备高电荷转移效率和强氧化还原能力.研究发现,构建Z型异质结光催化体系不仅可以减少本体电子-空穴的复合,使其在不同半导体材料上实现空间分离,具有光谱响应宽、电荷分离效率高和稳定性高等优势,而且能保持良好的氧化还原能力.在半导体材料领域,石墨相氮化碳(g-C₃N₄)作为一种无金属聚合物半导体,具有良好的热化学稳定性、电学和光学特性,但存在量子效率低和适用范围窄等局限性.而五氧化二钒(V₂O₅)是一种重要的过渡金属氧化物半导体,由于具有良好的电学和光学性能被广泛用于锂离子电池、气敏传感器和光电器件.V...     

9,9-二-(3-(9-苯咔唑基))-2,7-芘基芴的光电性质

芴类化合物作为有机电致发光材料近年来引起了人们的广泛关注, 其具有高亮度和高工作效率等性能. 本论文采用量子化学方法研究了一种新型的芴类发光材料, 9,9-二-(3-(9-苯咔唑基))-2,7-芘基芴的光电性质. 具体研究内容包括基态和激发态几何结构、前线分子轨道、能隙、电离能、电子亲和势、重组能以及吸收光谱和发射光谱等. 理论计算结果表明, 9,9-二-(3-(9-苯咔唑基))-2,7-芘基芴发射光谱为450.6 nm, 其在电致发光器件应用上是一种具有开发前景和实用价值的蓝光发光材料.     

2-苯基苯并噻吩合成的研究进展

2-苯基苯并噻吩是一类重要的化合物,广泛应用于医药、农药和半导体等功能性材料的合成。 因此,其合成受到人们广泛关注,合成新方法不断出现。 本文从不同反应底物类别出发,对2-苯基苯并噻吩的合成方法进行了简要的综述和评价。     

二维半导体合金的制备、结构和性质

原子层厚度的二维半导体材料因具有特殊的低维效应而被广泛研究. 面向光电器件应用, 需要可控调节二维半导体材料的能带结构, 包括带隙、价带/导带位置等. 合金方法是一种调控半导体能带的通用方法. 本综述介绍了近几年来二维半导体合金材料的研究进展, 包括材料的热力学稳定性、可控制备、结构表征和性质研究. 介绍的材料体系是过渡金属二硫族化物的单层合金材料, 金属元素主要是第六副族的Mo和W, 硫族元素主要是S和Se.     

CdS薄膜及其光电化学电池阳离子识别特性的研究

半导体材料CdS薄膜具有优良的光电特性,一直受到人们的关注,广泛用于许多无机薄膜太阳电池的n型窗口层[1,2]。用CdS薄膜组装的光电化学电池也一度引起人们的极大兴趣。二十世纪七十年代以来,半导体光电化学在光能-电能转换、光能-化学能转换和太阳能的光电化学利用方面得到了蓬     

高性能双极性聚合物半导体材料与晶体管器件

有机聚合物半导体材料与晶体管器件是融合了化学、材料、半导体以及微电子等学科的前沿交叉研究方向.聚合物半导体材料分子是该领域研究的重要内容,其中双极性聚合物分子半导体材料,兼具了电子和空穴的双重载流子输运能力而受到学术界的广泛关注.本文总结了双极性聚合物半导体材料与器件的研究进展,重点介绍了我们在D-A型双极性聚合物分子半导体材料设计、加工技术与器件制备以及功能应用方面的研究工作,并论述了双极性聚合物分子半导体材料与器件研究过程中存在的科学问题及发展方向.     

Effect of Zr and C Co-doping on the Optical Properties and Electronic Structure of TiO_2

The systematic trends and effect introduced by Zr and C co-doping to TiO2 of electronic structure and optical properties of anatase TiO2 have been calculated by the plane-wave ultra-soft pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for the exchange-correlation potential. Through the current calculations, the density of states (DOS), energy band structure and optical absorption coefficients have been obtained for TiO2 and compared with the doped TiO2, and the influence of electronic structure and optical properties caused by Zr and C co-doping has been presented qualitatively together. The results revealed that the energy band gap has been decreased owing to the doped Zr and C, whereas the optical absorption coefficients have been increased in the region of 400～800 nm and a red shift of absorption band can be found. Accordingly, photo catalytic activity of TiO2 has been enhanced. The current calculations are in good agreement with the experimental data.     

Band‐Edge Electronic Structure of β‐In2S3: The Role of s or p Orbitals of Atoms at Different Lattice Positions

As a promising solar‐energy material, the electronic structure and optical properties of Beta phase indium sulfide (β‐In₂S₃) are still not thoroughly understood. This paper devotes to solve these issues using density functional theory calculations. β‐In₂S₃ is found to be an indirect band gap semiconductor. The roles of its atoms at different lattice positions are not exactly identical because of the unique crystal structure. Additonally, a significant phenomenon of optical anisotropy was observed near the absorption edge. Owing to the low coordination numbers of the In3 and S2 atoms, the corresponding In3‐5s states and S2‐3p states are crucial for the composition of the band‐edge electronic structure, leading to special optical properties and excellent optoelectronic performances.     

The First-principles Calculations of the Electronic Structures and Optical Properties of Ⅱ-Ⅲ_2-Ⅵ_4(Ⅱ = Zn,Cd; Ⅲ = In; Ⅵ = Se,Te)

The electronic structures and optical properties of II?III2?VI4(II = Zn, Cd; III = In; VI = Se, Te) compounds are studied by the density functional theory(DFT) using the Vienna ab initio simulation package(VASP). Geometrical optimization of the unit cell is in good agreement with the experimental data. Our calculations show that the valence band maximum(VBM) and conduction band minimum(CBM) are located at G resulting in a direct energy gap. The optical properties are analyzed, and the independent second harmonic generation(SHG) coefficients are determined. By an analysis of the band structure, we can get that SHG response of the system can be attributed to the transitions from the bands near the top of valence band that are derived from the Se/Te p states to the unoccupied bands contributed by the p states of In atoms.     

Different Mixing Types CdSe‐CdS Nanocomposites

The optical properties of 2 mixing types of CdS‐CdSe nanoparticles (i.e., coprecipitated CdS‐CdSe nanoparticles, CdS‐coated CdSe (CdSe/CdS)) were studied. Results indicated that the co‐precipitated nanoparticles kept the similar optical properties of both CdS and CdSe's, while the CdS/CdSe core‐shell structure showed totally different optical properties from the simple components. We paid special attention to the core/shell structure, as the core‐shell structure showed a better passivating effect. Therefore, the XRD and TEM were tested on the core‐shell structure. XRD results showed that the diffraction patterns of core‐shell structure were roughly the same as their simple components. And the TEM indicated the core‐shell structure had a uniform dispersion in the solution.     

Evolution of Structural, Electronic and Optical Properties of Monoclinic ZrO2 under High Pressure： A First Principles Study

The structural, electronic and optical properties of the monoclinic ZrO2 were studied by ab initio calculations based on the density functional theory and pseudopotential method. The calculated lattice parameters and band gap are in agreement with the experimental and other theoretical values. The evolution of lattice parameters and electronic properties were illustrated under high pressure. Meanwhile, the optical properties, such as adsorption coefficients, imaginary part of dielectric function, and energy loss function, were investigated under both ambient and high pressures.     

Synthesis,Crystal and Band Structures,and Optical Properties of Mercury Pnictide Halide Hg19As10Br18

A mercury pnictide halide semiconductor Hg19As10Br18(1) has been prepared by the solid-state reaction and structurally characterized by single-crystal X-ray diffraction analysis.Compound 1 crystallizes in triclinic,space group P with a = 11.262(4),b = 11.352(4),c = 12.309(5) ,α = 105.724(2),β = 105.788(4),γ = 109.0780(10)° and V = 1314.3(8) 3.The structure of 1 is composed of parallel perovskite-like layers bridged by the linearly coordinated Br atoms to form a three-dimensional framework.The optical properties were investigated in terms of the diffuse reflectance spectrum.The electronic band structure along with density of states(DOS) calculated by DFT method indicates that compound 1 is a semiconductor with an indirect band gap,and that the optical absorption is mainly originated from the charge transitions from Br-4p and As-4p to the Hg-6s states.     

Ab initio study of electronic structure and optical properties of heavy-metal azides: TlN3, AgN3, and CuN3

Detailed ab initio studies on the electronic structure and optical properties of the heavy-metal azides have been performed using density functional theory within the generalized gradient approximation. An analysis of band structure, density of states, charge transfer, and bond order shows that the heavy-metal azides are ionic compounds but have covalent character. The valence bands of AgN3 and CuN3 are strongly dominated by Ag- and Cu-d, respectively, but that of TlN3 arises from the contributions of Tl-s and terminal N-p and not from Tl-d. The real and imaginary parts of the dielectric function, adsorption coefficient, and electron energy-loss spectra are calculated and compared with available experimental data.     

A theoretical study of the structural,thermoelectric, and spin-orbit coupling influenced optoelectronic properties of CsTmCl3 halide perovskite

This first principles study explores the structural, electronic, optical, and thermoelectric properties of the CsTmCl₃ halide perovskite using density functional theory. The structural and thermoelectric properties are calculated without considering the spin-orbit coupling (SOC), while both the electronic and optical properties are calculated with and without the SOC effect. A comparison of the results obtained with and without SOC reveals that inclusion of the SOC effect reduces the band gap from 1.18 to 0.99 eV due to shifting of the Tm-d states toward the Fermi level. However, direct nature of the band gap remains the same in both the cases. The effect of SOC on the optical properties is, however, only visible in shifting of the third characteristic peak to lower energies. Strong optical absorption in the visible and ultraviolet regions shows effectiveness of CsTmCl₃ in the optical devices working in these regions. Moreover, the calculated transport properties reveal CsTmCl₃ as a useful thermoelectric material at room temperature.     

Investigation of photoelectrical properties and relaxation dynamics in photoexcited CdSe nanocrystals in thin film form

Electrical and photoelectrical properties of cubic CdSe nanocrystals in thin film form (including the relaxation dynamics of photocarriers) are investigated. Photoelectrical properties of the obtained films are controlled by chemical (varying the reagent concentration in the reaction system) and physical means (controlling the crystal dimensions). In the case of thin films with optimal photoelectrical properties, the calculated band gap energy and ionization energies of impurity levels (on the basis of experimentally obtained temperature dependence of dark electrical resistance) at 0 K are 1.85, 0.74 and 0.43 eV, correspondingly. The calculated optical band gap energy (on the basis of spectral dependence of photoconductivity) at room temperature of 1.75 eV is in excellent agreement with the value of 1.77 eV which is obtained on the basis of electronic absorption spectrum in the framework of parabolic approximation for dispersion relation. Upon thermal treatment of chemically deposited thin films of cubic CdSe quantum dots, as a result of processes of coalescence and crystal growth, the electronic contact between nanocrystals increases and the confinement effects irreversibly disappear. Relaxation of non-equilibrium charge carriers is practically carried out according to the linear mechanism. The calculated relaxation time of photoexcited charge carriers is 0.4 ms.     

Type-II quantum dots: CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures

Type-II band engineered quantum dots (CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures) are described. The optical properties of these type-II quantum dots are studied in parallel with their type-I counterparts. We demonstrate that the spatial distribution of carriers can be controlled within the type-II quantum dots, which makes their properties strongly governed by the band offset of the comprising materials. This allows access to optical transition energies that are not restricted to band gap energies. The type-II quantum dots reported here can emit at lower energies than the band gaps of comprising materials. The type-II emission can be tailored by the shell thickness as well as the core size. The enhanced control over carrier distribution afforded by these type-II materials may prove useful for many applications, such as photovoltaics and photoconduction devices.