卤素、 氰基及N原子修饰对四硫富瓦烯衍生物载流子传输性质影响的理论研究

基于密度泛函理论结合跳跃模型和能带理论研究了氟、 氯、 氰基和N原子的引入对四硫富瓦烯(TTF)衍生物载流子传输性质的影响. 计算结果表明, 嵌N修饰会降低分子重组能, 特别是当N原子靠近TTF主体环时作用更明显. 与引入卤素修饰相比, 引入氰基修饰的分子具有更小的电子和空穴重组能及更低的前线分子轨道(FMO)能级. 同时迁移率的计算结果显示, 分子6具有1.15 cm²·V^-1·s^-1的高电子迁移率, 考虑其较低的LUMO能级, 推测其有望成为潜在的优异电子传输材料, 而相似的电子和空穴迁移率使分子2有望成为潜在的双极性传输材料. 同时还考察了S和N原子之间的弱相互作用, 当S或N原子对分子HOMO(或LUMO)有贡献时, 其相应的空穴(或电子)传输能力会有所提高.     

十字交叉型π共轭分子3,6-二苯-1,2,4,5-(2',2"-二苯基)-苯并二噁唑的电子结构和电荷传输性质的理论研究

采用密度泛函理论的B3LYP方法, 在6-31G(d)基组水平下研究了以三联苯和二苯基苯并噁唑构成的十字交叉型共轭分子3,6-二苯基-1,2,4,5-(2',2"-二苯基)-苯并二噁唑的电子结构和电荷传输性质. 通过对分子的重组能和晶体中分子间电荷传输积分的计算得到该分子的空穴迁移率为0.31 cm2·V -1·s -1 , 电子迁移率为0.11 cm2/(V·s). 计算结果表明, 空穴的传输主要是通过三联苯方向上两端苯环的"边对面"的相互作用以及分子中心π体系的错位重叠相互作用来实现的. 而电子的传输路径主要是通过苯并噁唑方向的π-π重叠相互作用来实现. 通过分析分子正负离子态的Mulliken电荷发现, 正电荷较多分布在三联苯方向上, 而负电荷较多分布在苯并噁唑方向上. 计算结果表明, 电子和空穴的传输分别在分子相互交叉的不同方向上, 有利于电子和空穴的平衡传输.     

氟代寡聚噻吩系列衍生物的载流子传输性质的理论研究

基于密度泛函理论方法, 采用Marcus电荷转移公式, 分别从几何和电子结构、 重组能、 转移积分及迁移率等方面研究了氟代寡聚噻吩系列衍生物中噻吩环个数、 全氟代苯位置的改变及F原子的引入对体系载流子传输性质的影响. 计算结果表明, 化合物1b, 1c和1d的电子迁移率随着噻吩单元个数的增加而逐渐升高, 因此可以通过增加噻吩单元个数来提高其电子迁移率; 而对于化合物1d, 2a和2b而言, 氟代苯位置的改变对传输性质产生了较大的影响, 其中化合物1d具有良好的平面性和π-π堆积, 传输性能最好, 有望成为良好的双极性传输材料; 比较化合物2b与3可以发现, F原子的引入增大了化合物2b的载流子迁移率, 为实验设计高迁移率的传输材料提供了理论依据.     

十字交叉型π共轭分子3,6-二苯-1,2,4,5-(2′,2″-二苯基)-苯并二噁唑的电子结构和电荷传输性质的理论研究

采用密度泛函理论的B3LYP方法, 在6-31G(d)基组水平下研究了以三联苯和二苯基苯并噁唑构成的十字交叉型共轭分子3,6-二苯基-1,2,4,5-(2′,2″-二苯基)-苯并二噁唑的电子结构和电荷传输性质. 通过对分子的重组能和晶体中分子间电荷传输积分的计算得到该分子的空穴迁移率为0.31 cm²·V^-1·s^-1, 电子迁移率为0.11 cm²/(V·s). 计算结果表明, 空穴的传输主要是通过三联苯方向上两端苯环的“边对面”的相互作用以及分子中心π体系的错位重叠相互作用来实现的. 而电子的传输路径主要是通过苯并噁唑方向的π-π重叠相互作用来实现. 通过分析分子正负离子态的Mulliken电荷发现, 正电荷较多分布在三联苯方向上, 而负电荷较多分布在苯并噁唑方向上. 计算结果表明, 电子和空穴的传输分别在分子相互交叉的不同方向上, 有利于电子和空穴的平衡传输.     

巯基偶氮苯单分子电子传输的取代基效应

用密度泛函理论B3LYP/6-31G**计算巯基偶氮苯分子及分子离子的空间构型和电子结构, 研究取代基对巯基偶氮苯单分子电子传输的影响. 结果表明, 拉电子基(—COOH、—NO2)的引入, 可以提高巯基偶氮苯单分子电子传输体系的稳定性, 使体系LUMO的离域性增高、S原子反应活性增强、HOMO-LUMO能隙显著减小, 进而降低电子传输能垒, 有利于分子电子传输. 相同取代基的分子离子比分子具有更小的HOMO-LUMO能隙, S—Au键更易形成, 金属-分子-金属结构的电子传输性更强.     

吲哚并咔唑类衍生物载流子传输性质的理论研究

以密度泛函理论结合跳跃模型, 重点研究了氯原子和烷基链的引入对吲哚并咔唑类衍生物传输性质的影响. 计算结果表明, 与吲哚并[3,2-b]咔唑(1)相比, 氯原子的引入增大了2,8-二氯吲哚并[3,2-b]咔唑(2)和2,8-二氯-5,11-二己基吲哚并[3,2-b]咔唑(3)的最高占据分子轨道(HOMO)的离域程度, 而对最低未被占据分子轨道(LUMO)则无显著贡献, 但明显降低了二者的能级. 上述结果表明, 对于LUMO, 氯原子体现了吸电子效应, 而对于HOMO, 氯原子体现了共轭效应. 烷基链的引入使化合物3的空穴迁移率明显高于化合物1和2, 这主要归因于化合物3具有更加紧密的分子堆积, 尤其在跳跃路径A中, 具有更大的分子间电子耦合和轨道重叠. 同时能带结构的计算结果进一步证明, 氯原子和烷基链的同时引入大大改善了吲哚并咔唑类衍生物的电荷传输性能.     

二邻苯二胺合镍(Ⅱ)载流子传输性能的理论研究

利用密度泛函理论UB3LYP方法, 对二邻苯二胺合镍(Ⅱ)(PHDANI)的基态和离子态几何结构进行全优化, 模拟其双自由基特性. 运用势能面曲线法计算了PHDANI的空穴和电子重组能. 从晶体结构中选出所有可能最近的载流子传输路径, 计算相应的传输积分, 结合Marcus电荷转移理论探讨PHDANI的载流子传输性质. 计算结果表明, 在单重态双自由基特性下, 空穴和电子的迁移率分别达到0.253和0.135 cm²·V^-1·s^-1, 空穴和电子传输迁移率都很高且能达到平衡, 从理论层面上阐明了PHDANI可以作为很好的双极性传输材料.     

“CH”/N取代对BTD衍生物光电性质影响的理论研究

采用量子化学方法研究了“CH”/N杂原子取代对2,1,3-苯并噻二唑衍生物(BTD)的电子性质、光谱性质以及电荷传输性质的影响,为新型有机发光材料的设计与合成提供了可靠的理论基础和指导.研究结果表明,在基态和激发态,与母体分子相比,“CH”/N取代同时降低了最高占据轨道和最低空轨道的能量.而且,与母体分子相比,“CH”/N取代衍生物的能隙升高.“CH”/N取代使母体分子吸收和发射光谱发生了蓝移,并且使发射光谱的振子强度增大.“CH”/N取代衍生物具有较小的空穴重组能,可以作为有机发光二极管的空穴传输材料.     

蒽类衍生物的电荷传输性质

以具有较高迁移率的对称取代类蒽的衍生物{2,6-二[2-(4-戊基苯基)乙烯基]蒽,DPPVAnt;2,6-二-噻吩蒽,DTAnt;2,6-二[2-己基噻吩]蒽,DHTAnt}为研究对象,采用密度泛函理论的B3LYP方法,在6-31G(d)的基组水平上研究了三种蒽类衍生物的分子结构、电子结构、重组能和电荷传输积分,采用Einstein关系式计算了室温下的载流子迁移率,并与蒽的相关计算结果进行了比较.DPPVAnt是较好的空穴传输材料,其空穴迁移率为0.49cm2·V-1·s-1;DHTAnt有利于电子传输,其电子迁移率为0.12cm2·V-1·s-1;而DTAnt是一种较好的双极性材料,其空穴迁移率和电子迁移率分别为0.069和0.060cm2·V-1·s-1.计算得到的迁移率与实验结果处于同一数量级.三种蒽类衍生物的电子重组能与蒽的相近,而空穴重组能均大于蒽的空穴重组能,大小顺序为蒽DPPVAntDTAntDHTAnt.这与计算的迁移率结果不一致,说明分子的堆积结构决定材料的电荷传输性质.     

CO诱导的FeO(111)/Ru(0001)负载Au原子吸附位和电荷的改变

采用密度泛函理论研究了CO气氛对FeO(111)/Ru(0001)负载Au原子吸附位、电荷及其稳定性的影响. 首先考察了FeO(111)单层薄膜在Ru(0001)表面上的界面结构. 研究发现,表面莫尔超晶胞内的HCP区域有最小的Fe-O层间距(rumpling),且Fe和O原子均与衬底Ru形成化学键. Au原子在FeO/Ru(0001)上最稳定的吸附在HCP区域的Fe-bridge位. 其中,Au原子诱导两个Fe原子从O原子层的下面翻转到其上面,形成两个Au-Fe键,且Au带负电. 当把体系暴露在CO气氛下后,CO能诱导Au原子从原来最稳定的Fe-bridge位转移到其邻近的O-top位,伴随着Au的电荷从负变到正,形成非常稳定的Au⁺-CO羰基物. 结果表明,反应气氛对负载金属催化剂的化学状态及其稳定性的影响很大; 同时也强调了反应条件下催化剂原位表征的重要性.     

CO在M55（M=Cu,Ag,Au）团簇上吸附的密度泛函研究

在全电子相对论BVP86/DNP水平下对CO在Au55,Ag55和Cu55团簇上的吸附进行了比较研究,并考察了电荷对吸附的影响.计算结果表明,CO在Au55团簇上吸附能最大,其次为Cu55团簇,最弱的为Ag55团簇.团簇电荷对C—O键活化和CO与团簇表面原子成键影响较小.金团簇的电荷对吸附能影响较大,而银和铜团簇的电荷对吸附能影响较小.CO吸附到团簇上导致团簇上电子向CO转移.C—O键活化强度与吸附位置密切相关,其中孔位吸附导致C—O键活化程度最大,最弱的为顶位吸附.CO在金团簇上吸附具有较好选择性,而在银和铜团簇上吸附无选择性.     

Charging energy and barrier height of pentacene on Au(111): a local-orbital hybrid-functional density functional theory approach

We analyze the pentacene/Au(111) interface by means of density functional theory (DFT) calculations using a new hybrid functional; in our approach we introduce, in a local-orbital formulation of DFT, a hybrid exchange potential, and combine it with a calculation of the molecule charging energy to properly describe the transport energy gap of pentacene on Au(111). Van der Waals forces are taken into account to obtain the adsorption geometry. Interface dipole potentials are also calculated; it is shown that the metal/pentacene energy level alignment is determined by the potential induced by the charge transfer between the metal surface and the organic material, as described by the induced density of interface states model. Our results compare well with the experimental data.     

Density functional theory study on electron and hole transport properties of organic pentacene derivatives with electron-withdrawing substituent

Attaching electron-withdrawing substituent to organic conjugated molecules is considered as an effective method to produce n-type and ambipolar transport materials. In this work, we use density functional theory calculations to investigate the electron and hole transport properties of pentacene (PENT) derivatives after substituent and simulate the angular resolution anisotropic mobility for both electron and hole transport. Our results show that adding electron-withdrawing substituents can lower the energy level of lowest unoccupied molecular orbital (LUMO) and increase electron affinity, which are beneficial to the electron injection and ambient stability of the material. Also the LUMO electronic couplings for electron transport in these pentacene derivatives can achieve up to a hundred meV which promises good electron transport mobility, although adding electron-withdrawing groups will introduce the increase of electron transfer reorganization energy. The final results of our angular resolution anisotropic mobility simulations show that the electron mobility of these pentacene derivatives can get to several cm(2) V(-1) s(-1), but it is important to control the orientation of the organic material relative to the device channel to obtain the highest electron mobility. Our investigation provide detailed information to assist in the design of n-type and ambipolar organic electronic materials with high mobility performance.     

Influence of lattice dynamics on charge transport in the dianthra[2,3-b:2',3'-f]-thieno[3,2-b]thiophene organic crystals from a theoretical study

The influence of lattice dynamics on carrier mobility has received much attention in organic crystalline semiconductors, because the molecular components are held together by weak interactions and the transfer integrals between neighboring molecular orbitals are extremely sensitive to small nuclear displacements. Recently, it has been shown that the dynamic disorder has little effect on hole mobility in the ab plane of pentacene, but a reasonable explanation is absent for such a puzzle. To better understand the effect of lattice vibrations on carrier transport, a further study is required for other organic materials. In this work, a mixed molecular dynamic and quantum-chemical methodology is used to assess the effect of nuclear dynamics on hole mobility in the dianthra[2,3-b:2',3'-f]-thieno[3,2-b]thiophene (DATT) crystals which exhibit high air stability with the hole mobility as large as that in rubrene-based devices. It is found that the lattice vibrations lead to an increasing encumbrance for hole transport in the ab plane of the DATT crystals as the temperature increases. By comparing the crystal structures of DATT and pentacene, the reduced hole mobility in DATT is attributed to the unsymmetric arrays of nearest-neighboring molecular dimers in the ab plane, because the electronic coupling exhibits unbalanced thermal fluctuations for the nearest-neighboring dimers which then induces a stronger oscillation for carriers along the directions with asymmetric packing. To further relate the dynamic disorder with hole transport, the variations of anisotropic mobilities are also analyzed. As a result, the negligible effect of lattice dynamics on the hole mobility in pentacene is explained by the centrosymmetric molecular packing of the nearest-neighboring molecular pairs in the ab plane.     

苯丙炔酸和苯丙烯酸酯苯并菲盘状液晶电荷传输的理论研究

电荷传输是有机材料的重要性质之一．根据电子转移的半经典模型对含苯丙炔酸和苯丙烯酸酯支链的苯并菲盘状液晶化合物分子的电荷传输性质进行理论研究．研究结果表明,所计算的三个苯并菲衍生物分子均具有高的电荷传输性能．标题化合物分子的负电荷传输速率均比苯并菲大,含苯丙烯酸酯链的苯并菲分子比含苯丙炔酸酯链的苯并菲分子具有较大的空穴传输速率及较小的负电荷传输速率．对于含苯丙烯酸酯链的苯并菲分子,链烷氧基越长,正电荷传输速率越大,负电荷传输速率越小．     

Positional Effect of the Triphenylamine Group on the Optical and Charge‐Transfer Properties of Thiophene‐Based Hole‐Transporting Materials

Hybrid organic‐inorganic perovskite solar cells (PSCs) have shown significant potential for use in the energy field. Typically, hole‐transporting materials (HTMs) play an important role in affecting the power conversion efficiency (PCE) of PSCs. A deep understanding of the structure‐property relationship plays a vital role in developing efficient HTMs. Herein, the relationship between the structure and properties of two small organic HTMs H2,5 and H3,4 were systematically investigated in terms of the electronic and optical properties, the hole‐transporting behavior by using density functional theory (DFT) and Marcus electron transfer theory. The results demonstrated that the high power conversion efficiency of the H2,5‐ based PSC was caused by strong interactions with the perovskite material on the interface and an enhanced hole mobility in H2,5 compared with H3,4 . The strong interaction derives from the short bond length of O atom of HTM and Pb atom of perovskite material, and the highly hole mobility derives from the quasi‐planar conjugated conformation and tight packing model of neighboring molecules in H2,5 . In addition, we found that the planar structure enhances the intermolecular interaction between HTM and perovskite materials compared with the ′V′‐shaped molecule. Importantly, we also note that the HOMO level of the isolated molecule is not always proportional to the open‐circuit voltages of PSCs since the HOMO level might move toward a higher level when the interaction between HTM and interface of perovskite was included. The work gives essential information for rational designing efficient HTMs.     

Keggin型多酸负载的单原子催化剂(M1/POM,M = Ni,Pd, Pt,Cu, Ag,Au, POM = [PW12O40]3-)活化氮气分子的密度泛函理论计算研究

采用量子化学密度泛函理论(DFT)结合自然键轨道(NBO)分析的方法对一系列以多酸为载体的单原子催化剂(SACs)(M₁/POM (M = Ni, Pd, Pt, Cu, Ag, Au, POM = [PW₁₂O₄₀]^3-)的分子几何、电子结构及红外光谱进行计算。结果表明,Pt₁/POM对N₂分子具有潜在的活化能力,Pt₁/POM与N₂相互作用主要来自于由金属Pt的d_xz和d_yz轨道与N₂的π^*反键轨道重叠,金属Pt的d_xz、d_yz轨道上的电子填充到了氮气的π^*反键轨道上弱化了N≡N成键,导致了N≡N之间的键长增大,有效的活化了氮气分子。对它们红外光谱的分析表明,Keggin型多酸负载金属后W―O_c―W振动吸收峰发生劈裂,产生了五个典型的红外特征吸收峰。     

Geometries, stabilities, and electronic properties of small anion Mg-doped gold clusters: a density functional theory study

First-principle density functional theory is used for studying the anion gold clusters doped with magnesium atom. By performing geometry optimizations, the equilibrium geometries, relative stabilities, and electronic and magnetic properties of [Au(n)Mg]? (n = 1-8) clusters have been investigated systematically in comparison with pure gold clusters. The results show that doping with a single Mg atom dramatically affects the geometries of the ground-state Au(n+1)? clusters for n = 2-7. Here, the relative stabilities are investigated in terms of the calculated fragmentation energies, second-order difference of energies, and highest occupied?lowest unoccupied molecular orbital energy gaps, manifesting that the ground-state [Au(n)Mg]? and Au(n+1)? clusters with odd-number gold atoms have a higher relative stability. In particular, it should be noted that the [Au?Mg]? cluster has the most enhanced chemical stability. The natural population analysis reveals that the charges in [Au(n)Mg]? (n = 2-8) clusters transfer from the Mg atom to the Au frames. In addition, the total magnetic moments of [Au(n)Mg]? clusters exhibit an odd-even oscillation as a function of cluster size, and the magnetic effects mainly come from the Au atoms.     

Theoretical insights into the 1D‐charge transport properties in a series of hexaazatrinaphthylene‐based discotic molecules

Discotic liquid crystal (DLC) materials have attracted considerable attention mainly due to their high charge carrier mobilities in quasi‐one‐dimensional columns. In this article, five hexaazatrinaphthylene‐based DLC molecules were investigated theoretically, and their frontier molecular orbital energy levels, crystal structures, and electron/hole drift mobilities were calculated by combination of density functional theory (DFT) and semiclassical Marcus charge transfer theory. The systems studied in this work include three experimentally reported molecules ( 1 , 2 , and 3 ) and two theoretically designed molecules ( 4 and 5 ). Compared with the 1 – 3 compounds, 4 and 5 have three more extended benzene rings in the π‐conjugated core. The present results show that the orders of the frontier molecular orbital energy levels and electron drift mobilities agree very well with the experiment. For 4 and 5 , the electron/hole reorganization energies are lower than those of compounds 1 – 3 . Furthermore, the calculated electron/hole transfer integral of 5 is the largest among all the five systems, leading to the highest electron and hole mobilities. In addition, the hydrophobicity and solubility were also evaluated by DFT, indicating that compound 5 has good hydrophobicity and good solubility in trichloromethane. As a result, it is expected that compound 5 can be a potential charge transport material in electronic and optoelectronic devices. © 2017 Wiley Periodicals, Inc.     

Charging of Au atoms on TiO2 thin films from CO vibrational spectroscopy and DFT calculations

Au atoms have been deposited on oxidized and reduced TiO2 thin films grown on Mo(110). The gold binding sites and the occurrence of Au-TiO2 charge transfer were identified by measuring infrared spectra as a function of temperature and substrate preparation. The results have been interpreted by slab model DFT calculations. Au binds weakly to regular TiO2 sites (De < 0.5 eV) where it remains neutral, and diffuses easily even at low temperature until it gets trapped at strong binding sites such as oxygen vacancies (De = 1.7 eV). Here, a charge transfer from TiO2 to Au occurs. Au(delta-)CO complexes formed on oxygen vacancies easily lose CO (De = 0.4 eV), and the CO stretching frequency is red-shifted. On nondefective surfaces, CO adsorption induces a charge transfer from Au to TiO2 with formation of strongly bound Audelta+CO complexes (De = 2.4 eV); the corresponding CO frequency is blue-shifted with respect to free CO. We propose possible mechanisms to reconcile the observed CO desorption around 380 K with the unusually high stability of Au-CO complexes formed on regular sites predicted by the calculations. This implies: (a) diffusion of AuCO complexes above 150 K; (b) formation of gold dimers when the diffusing AuCO complex encounters a Au atom bound to an oxygen vacancy (reduced TiO2) or a second AuCO unit (oxidized TiO2); and (c) CO desorption from the resulting dimer, occurring around 350-400 K.