Thermally activated delayed fluorescence host materials based on triphenylphosphine oxide derivatives

Abstract

Novel thermally activated delayed fluorescence (TADF) host molecules for blue electrophosphorescence were developed by combining the electron donor acridine derivatives with the electron acceptor triphenylphosphine oxide unit in a single molecule based on density functional theory. We obtained the energies of the first excited singlet (S₁) and triplet (T₁) states of the TADF materials by performing procedures in accordance with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to the ground state using dependence on the charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. Using DFT and TD-DFT calculations, the significant separation between the HOMO and LUMO caused a small difference in energy (ΔE_ST) between the S₁ and T₁ states. The host molecules retained high triplet energy and showed great potential for use in blue phosphorescent organic light-emitting diodes. The results also showed that these molecules are promising TADF host materials because they demonstrate a low barrier to hole and electron injection, balanced charge transport for both holes and electrons, and small ΔE_ST.     

Y2O3掺杂ZrO2配合物的分子结构和光谱特性的理论研究

本文应用密度泛函理论指导人们深入理解氧化锆溶胶中分子的结构和光谱性能,探讨了溶胶中锆配合物的结构参数、光谱特性和原子的Mulliken 电荷布局. 理论结果表明掺杂引起粒径尺寸减少是由于掺杂引起氧桥聚合速度减慢和颗粒间吸引力的减弱.此外,振动光谱分析表明锆配位前驱体的有序化和第二相掺杂剂的引入明显减少了单斜氧化锆的特征光谱.理论分析结果很好地符合了实验结果.     

Theoretical Design Study on the Electronic Structures and Phosphorescent Properties of Four Iridium(III) Complexes

The geometry structures, electronic structures, absorption, and phosphorescent properties of four Ir(III) complexes have been investigated using the density functional method. Calculations of ionization potential (IP) and electron affinity (EA) were used to evaluate the injection abilities of holes and electrons into these complexes. The result also indicates that the –CF₃ substituent group on the ligand not only change the character of transition but affect the rate and balance of charge transfer. The lowest energy absorption wavelengths are located at 428 nm for 1a, 446 nm for 1b, 385 nm for 2a, and 399 nm for 2b, respectively, in good agreement with the energy gap (ΔE_L-H) trend because the HOMO–LUMO transition configurations are predominantly responsible for the S₀→S₁ transition. 2b has the 433 nm blue emission, which might be a potential candidate for blue emitters in phosphorescent dopant emitters in organic light emitting diodes (OLEDs). The study could provide constructive information for designing novel OLEDs materials in the future.

[Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.]     

Ca掺杂MgF2光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了Ca掺杂MgF2晶体的几何结构、电子结构以及光学性质.结果表明:适量比例的Ca掺杂导致MgF2晶体禁带宽度变窄.在一定能量范围内,Ca掺杂对MgF2晶体的介电常数和吸收系数有调制作用,吸收系数增加有利于光生电子-空穴对的有效分离,提高了MgF2光催化效率,揭示了Ca掺杂MgF2体系在光催化方面的潜在应用.     

Synthesis and Properties of New Imidazole Derivatives Including Various Chromophore for OLEDs

Abstract

Two new blue compounds were successfully synthesized by introducing phenanthroimidazole group as a side group into pyrene, a chromophore with good luminous efficiency: 1-(4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-2-(pyren-1-yl)-1H-phenanthro[9,10-d]imidazole (NA-PPI) and 1-(4'-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)-2-(pyren-1-yl)-1H-phenanthro[9,10-d]imidazole (CP-PPI). The optical and electroluminescence properties of newly synthesized materials were measured. Both materials emit blue or sky-blue photoluminescence in the film state and have a high PLQY value of over 80% in solution state. The synthesized materials were applied as EML in non-doped devices, and high efficiency of 3.51?cd/A and EQE of 2.39% in CP-PPI device were achieved.     

Theoretical study on the electronic structures and spectral properties of two series of osmium(II) complexes with different substituent groups

Two series of osmium(II) complexes with different substituent groups (-CF₃, -N(CH₃)₂) have been studied by using the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, to investigate their electronic structures, absorption, and emission properties. The influence of different substituted groups on their photophysical properties has also been explored. The lowest energy absorption and emission wavelengths calculated are in good agreement with the available experimental values. Besides, ionization potential (IP), electron affinities (EA), and reorganization energy (λ) were calculated to evaluate the charge transfer and balance properties between hole and electron. It is expected that the theoretical studies could provide valuable information for the phosphorescent osmium(II) material for use in the organic light-emitting diodes.     

SrCl2∶Ag2+晶体局部结构及电子顺磁共振参量的理论研究

基于离子簇模型,采用d9离子在四角伸长八面体对称中电子顺磁共振(EPR)参量的高阶微扰公式,计算了SrCl2中四角Ag2+中心的EPR参量(g因子g//,g⊥和超精细结构常数A因子A//,A⊥).由于体系的共价性及配体Cl-较大的旋轨耦合系数,在这些公式中同时考虑了配体轨道及旋轨耦合作用对EPR参量的贡献.公式里的能级分裂由重叠模型和杂质中心的局部结构确定.研究发现,掺杂后由于尺寸失配,杂质Ag2+沿着C4轴有一个很大的非中心位移,到最近邻的Cl-平面距离约为0.060 nm.计算所得的EPR理论值与与实验值符合的很好.     

Desynchronization of Pedal Motion: Crystallographic and Theoretical Study of (<Emphasis Type="Italic">E</Emphasis>)-4-[(4-ethylphenyl)diazenyl]-2-methylphenol

Abstract  The single crystal X-ray diffraction analysis of the title compound, C₁₅H₁₆N₂O, reveals that its molecules exhibit whole-molecule disorder at both crystal lattice sites due to pedal motion in solid state. The compound crystallizes in the monoclinic space group P 2₁/c with a = 20.5504(14) ?, b = 10.8887(5) ?, c = 12.0191(8) ? and β = 96.927(5)°. While major pedal conformers of the compound in solid state are stabilized by intermolecular O–H···N type hydrogen bonds leading to the formation of C(7) chains at Site 1 and C(8) chains at Site 2 along [0 1 0] axis, C–H···π type intermolecular interactions between major and minor conformers also serve to stabilize minor pedal conformers. An interesting feature about the crystal structure is that pedal conformers at Site 1 have two different occupancy factors arising from desynchronization of pedal motion along [2 1 0] direction in crystal phase. Quantum chemical calculations at the B3LYP/6-31++G** level suggest that the desynchronization of pedal motions make more unstable pedal conformers at Site 1 than those at Site 2. Index Abstract  Molecular and crystal structure of (E)-4-[(4-ethylphenyl)diazenyl]-2-methylphenol, C₁₆H₁₈N₂O, indicate desynchronization of pedal motion and the quantum chemical calculations at level of B3LYP/6-31++G** suggest that desynchronization of pedal motions make more unstable pedal conformers.      

Theoretical Calculations on Hydroxybutyl 4-aroyloxybenzoates: Synthesis and Mesomorphic Properties of their H-bonded Complexes with Poly(4-vinylpyridine)

Important parameters of hydroxybutyl 4-aroyloxybenzoate ligands were calculated and correlations were made between theoretical and experimental results. In addition, supramolecular side-chain liquid crystalline polymers of the ligands with poly(4-vinylpyridine) were synthesized. Hydrogen bond formation was ascertained by Fourier tranform infra-red spectroscopy. The stabilities of the complexes were determined by thermogravimetric analysis. The mesomorphic behavior was investigated using differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction analysis. Semiempirical study revealed that a ratio of ～1.2 in the lengths of flexible and rigid parts of the molecules is the most favorable for a wider liquid crystal (LC) temperature range.     

TOPCon太阳电池发射极Al2O3/SiNx与SiO2/Al2O3/SiNx叠层膜钝化性能的比较

本文对TOPCon电池发射结的叠层钝化膜进行了研究,对比了3种不同叠层钝化膜(SiO₂/SiN_x、Al₂O₃(1.5 nm)/SiN_x、SiO₂/Al₂O₃(1.5 nm)/SiN_x)的钝化性能。结果表明:Al₂O₃(1.5 nm)/SiN_x的钝化性能优于SiO₂/SiN_x,SiO₂/Al₂O₃(1.5 nm)/SiN_x的钝化水平最佳,隐开路电压均值可达到705 mV。基于Al₂O₃/SiN_x叠层膜研究了Al₂O₃厚度(1.5 nm、3 nm和5 nm)对钝化性能和电池转换效率的影响。当Al₂O₃厚度由1.5 nm增加到3 nm时,钝化性能得到明显提升,隐开路电压均值提高了20 mV,达到707 mV,对应电池的光电转换效率升高了0.23个百分点,与SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜电池的转换效率持平。然而,当Al₂O₃厚度继续增加至5 nm时,隐开路电压均值保持不变。因此可以使用Al₂O₃(3 nm)/SiN_x叠层膜代替SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜,不仅简化了电池的工艺步骤,而且降低了生产成本。     

Synthesis and Structural Comparison for a Series of Cr(II) (iodo) NacNac Complexes

Abstract  A series of complexes of the form [bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato](iodo)(solvent) chromium were synthesized and structurally characterized (solvent = tetrahydrofuran, acetonitrile, α-picoline). The tetrahydrofuran adduct crystallized in the P2₁/n space group with the crystal cell parameters a = 17.628(6) ?, b = 10.218(3) ?, c = 20.646(7) ?, β = 109.209(4)°, V = 3512(2) ?³ and Z = 4. The acetonitrile adduct crystallized in the P2₁/c space group with the crystal cell parameters a = 16.104(7) ?, b = 11.965(5) ?, c = 18.201(8) ?, β = 116.091(6)°, V = 3150(2) ?³ and Z = 4. The α-picoline adduct crystallized in the C2/c space group with the crystal cell parameters a = 39.982(9) ?, b = 11.637(2) ?, c = 16.560(4) ?, β = 108.085(4)°, V = 7325(3) ?³ and Z = 8. For each compound, the coordination around each chromium center is square planar with varying degrees of distortion. Graphical Abstract  A series of Cr(II) complexes of the form LCrI(S) (where L = nacnac = β-diketiminate; S = solvent) were synthesized and structurally characterized.      

Growth and characterization of two-dimensional crystals for communication and energy applications

This review article covers the growth and characterization of two-dimensional (2D) crystals of transition metal chalcogenides, h-BN, graphene, etc. The chemical vapor transport method for bulk single crystal growth is discussed in detail. Top-down methods like mechanical and liquid exfoliation and bottom-up methods like chemical vapor deposition and molecular beam epitaxy for mono/few-layer growth are described. The optimal characterization techniques such as optical, atomic force, scanning electron, and Raman spectroscopy for identification of mono/few-layer(s) of the 2D crystals are discussed. In addition, a survey was done for the application of 2D crystals for both creation and deterministic transfer of single-photon sources and photovoltaic systems. Finally, the application of plasmonic nanoantenna was proposed for enhanced solar-to-electrical energy conversion and faster/brighter quantum communication devices.     

纳米硅制备过程中微结构与反应气体流量之间的关系研究

利用LICVD方法制备了纳米硅颗粒.研究了不同反应气体流量条件下,纳米硅微结构的转变规律,分析了制备工艺参数对纳米硅微结构的影响机制.研究表明,在激光功率密度恒定条件下,随着反应气体流量的增加,所制备纳米硅颗粒的尺寸逐渐变小,微结构中非晶态比例随反应气流的增加而增加.     

微晶硅薄膜纵向不均匀性的Raman光谱和AFM研究

本文研究了采用VHF-PECVD技术制备的微晶硅薄膜的纵向均匀性.喇曼测试结果显示:微晶硅薄膜存在着生长方向的结构不均匀,随厚度的增加,材料的晶化率逐渐变大;不同衬底其非晶孵化点是不一样的,对于同一种衬底,绒度大相应的晶化率就大,对应着孵化层的厚度小;AFM测试结果明显的给出:材料的结构随厚度增加发生变化.     

Synthesis,Crystal Structure and Fluorescent Study of Bis(2-(2-hydroxyphenyl)benzimidazolate)zinc with Ethanol Solvate

Abstract  The zinc(II) complex with 2-(2-hydroxyphenyl)benzimidazole, namely [Zn(2-(2-hydroxyphenyl)benzimidazolate)₂]·C₂H₅OH (1 · C₂H₅OH) has been synthesized and characterized by X-ray crystallography and photoluminescent analysis. The complex crystallizes in monoclinic space group P2₁/c with cell parameters a = 10.156(1) ?, b = 25.771(3) ?, c = 9.674(1) ?, α = 90°, β = 103.641(2)°, γ = 90°, Z = 4, V = 2460.4(4) ?³. The central Zn(II) is four-coordinate and has a tetrahedral geometry. The steady-state and time-resolved photoluminescent spectra for the title compound have also been studied. The emission property can be ascribed to ligand-centered charge-transfer transition (LCCT) with π → π* property. Index Abstract   A new co-crystal of Zn(II) complex of 2-(2-hydroxylphenyl)benzimidazole with ethanol solvate has been prepared, characterized by X-ray crystallography and fluorescent studies.      

共生晶体Mn2Hg4(SCN)12和MnHg(SCN)4的形成

采用恒温蒸发法从水溶液中生长Hg2+、Mn2+为双配位中心的SCN- 的配合物晶体.生长液中Hg2+含量较SCN-适当过量的条件下,出现Mn2Hg4(SCN)12晶体和MnHg(SCN)4晶体共生现象.MnHg (SCN)4晶体中Hg2+只与SCN-配位,Mn2+只与NCS-配位,而Mn2Hg4(SCN)12晶体中部分Hg2+可以同时与SCN-和NCS-配位体结合,并且部分SCN-同时和2个Hg2+结合成桥式结构.Mn2Hg4(SCN)12晶体中Mn2+的配位数由MnHg(SCN)4晶体中的4配位增大为5配位和6配位.Mn(NCS)4-6 和Mn(NCS)3-5 配位多面体的存在使Mn2Hg4(SCN)12晶体的颜色比MnHg(SCN)4晶体的颜色浅.     

抗菌建材关键微纳晶体合成与表征

本文采用水热法合成了层状晶体结构的磷酸锆钠抗菌剂载体,采用TEM、XRD、FTIR对合成的材料进行表征.材料呈微纳米颗粒形貌,结晶度较高,官能团符合磷酸锆钠的特征.通过银粒子负载,并模拟了应用环境下的抗菌测试,发现其具有明显的抑制菌群生长的功效.循环测试发现,经过吸附-抗菌以后的材料官能团没有发生变化,显示了较好的稳定性和循环利用性能.     

热丝化学气相法生长单晶金刚石颗粒的衬底温度场仿真及实验研究

本文使用金刚石磨料作为晶种颗粒,通过热丝化学气相法生长出单晶金刚石颗粒,并且建立三维的有限元模型,利用有限元仿真分析了生长过程中影响金刚石磨料生长速率以及沉积质量的各种因素,如热丝的排列方式,衬底的温度场,以及晶种的分布方式.通过固定在热丝CVD反应腔里的热电偶测量了实际的衬底温度分布,从而验证了仿真结果的正确性.另外,通过改变仿真模型优化了沉积单晶金刚石颗粒的工艺参数,获得适应于合成单晶金刚石颗粒的新技术,为化学气相沉积合成单晶金刚石颗粒奠定了基础,也为高温高压金刚石磨料品级的改进与提高提供了新途径.     

Study of the Nature and Distribution of Elementary Steps on the (100) Cleavage Faces of MgO Single Crystals by Atomic Force Microscopy

Some observations made on the nature and distribution of monolayer (elementary) steps on the (100) cleavage faces of MgO single crystals by atomic force microscopy are presented and discussed. The following types of patterns of monolayer steps are described: (1) trains of steps, (2) steps terminating on the cleaved surface at the emergence points of screw dislocations, and (3) localized pinning of advancing steps at random sites (probably at the emergence points of edge dislocations). It is shown that: (1) the origins of emergence points of monolayer steps are devoid of hollow cores due to a small Burgers vector of dislocations and (2) the minimum distance between two emerging steps due to screw dislocations and between two pinning centres due to edge dislocations depends on their sign, and is determined by the mutual interaction between neighbouring dislocations.