Tuning the helical twisting power of nematic liquid crystals induced by chiral 1, 2-propanediol derivatives using varied substituents

In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host(SLC-1717).The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.     

表面电荷转移掺杂石墨烯的研究进展

表面电荷转移掺杂是调制石墨烯电学特性的重要手段。发展高效、稳定的表面电荷转移掺杂剂对于提高石墨烯的电学和光电性能、从而推动其在电子和光电领域中的应用具有重要意义。本文围绕高效与稳定两个方面综述了近年来石墨烯表面电荷转移掺杂剂的研究现状以及掺杂石墨烯在光电器件应用方面的进展。根据掺杂剂的类型，着重介绍了最新发展的高效p型和n型掺杂剂，并概述了稳定掺杂方面的重要研究工作。此外，专门介绍了基于掺杂石墨烯透明电极的高性能光电器件。最后，根据表面电荷转移掺杂研究面临的主要挑战，对其未来的发展方向进行了展望。     

三(五氟苯基)硼烷掺杂有机/高分子半导体的研究进展

有机/高分子共轭聚合物的结构设计是制备高性能有机半导体的有效策略,但该过程存在着设计合成周期长、制备步骤复杂和产率偏低等问题。为了克服这些问题,近年来人们越来越关注对有机/高分子半导体的掺杂。然而,传统电荷转移掺杂剂(如卤族单质I₂、金属氧化物Fe₃O₄、小分子F4TCNQ等)存在掺杂效率低、溶解度差和掺杂条件苛刻等问题。相比之下,三(五氟苯基)硼烷具有溶解度高、掺杂效率高、广泛适应性等优点。本文结合相关文献综述了三(五氟苯基)硼烷掺杂有机半导体的物理机制,并探讨了掺杂有机半导体的性质;此外,还总结了三(五氟苯基)硼烷掺杂在不同光电功能器件中的应用并明确了今后的研究方向。     

Wide Band‐Gap Bismuth‐based p‐Dopants for Opto‐Electronic Applications

Ten new efficient p‐dopants for conductivity doping of organic semiconductors for OLEDs are identified. The key advantage of the electrophilic tris(carboxylato) bismuth(III) compounds is the unique low absorption of the resulting doped layers which promotes the efficiency of OLED devices. The combination of these features with their low fabrication cost, volatility, and stability, make these materials very attractive as dopants in organic electronics.     

Sterically-Hindered Molecular p-Dopants Promote Integer Charge Transfer in Organic Semiconductors

Molecular p-dopants designed to undergo electron transfer with organic semiconductors are typically planar molecules with high electron affinity. However, their planarity can promote the formation of ground-state charge transfer complexes with the semiconductor host and results in fractional instead of integer charge transfer, which is highly detrimental to doping efficiency. Here, we show this process can be readily overcome by targeted dopant design exploiting steric hindrance. To this end, we synthesize and characterize the remarkably stable p-dopant 2,2′,2′′-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)acetonitrile) comprising pendant functional groups that sterically shield its central core while retaining high electron affinity. Finally, we demonstrate it outperforms a planar dopant of identical electron affinity and increases the thin film conductivity by up to an order of magnitude. We believe exploiting steric hindrance represents a promising design strategy towards molecular dopants of enhanced doping efficiency.     

Influence of long-chain aliphatic dopants on the spectroscopic properties of polyketimine containing 3,8-diamino-6-phenylphenanthridine and ethylene linkage in the main chain. Noncovalent interaction: proton transfer, hydrogen and halogen bonding

The spectroscopic properties of the aromatic polyketimine containing 3,8-diamino-6-phenylphenanthridine and ethylene linkage in the main chain (PK1) before and after doping are dominated by an interplay of electron-donating and electron-withdrawing effects mediated by its nitrogen atom and active groups in the dopants, respectively. Hydrogen and halogen bond formation or molecular recognition between PK1 and decanoic acid (DCA), n-decyl alcohol (DA), 1,10-dibromodecane (DBr), and n-decyl sulfonic acid (DSA) was investigated in comparison with undoped PK1. UV-vis and Fourier transform infrared (FTIR) absorption, wide-angle X-ray diffraction (WAXD), and the atomic force microscopy (AFM) technique are used to probe the spectroscopic properties of the phenanthridine "core" of PK1 as well as its complexes. Spectral changes were observed for the PK1 after doping, which supported the ionic, hydrogen, and halogen bond formation between the PK1 and protonation agents (dopants). This specific interaction of the dopant with the host polymer influences the polyketimine properties, and the following changes were observed: (i) changes in the band gap (E(g)) of the protonated polyketimine, (ii) changes in the FTIR spectra of doped PK1, (iii) changes in optical micrographs of the protonated PK1 (detected by the AFM technique), and (iv) changes in crystalline structure of doped PK1. Our study demonstrates how the properties of conjugated PK1 can be tuned by the supramolecular engineering concepts, which could be important for optoelectronic applications of the materials.     

氮掺杂石墨烯的p型场效应及其精细调控

Functionalized graphene has attracted significant interest over the past decade due to its unique physical properties and potential applications. Graphene oxide (GO), a readily scaled-up product, is a basic material for further functionalization. Using reductive processes, highly conductive reduced graphene oxide (RGO) can be obtained, which exhibits electrical and optical properties analogous to those of graphene. Moreover, due to the presence of oxygen-containing functional groups, its chemical reactivity and electronic properties can be easily tailored by chemical doping with nitrogen. However, developing strategies for doping graphene is challenging and the fundamental roles of the doping atom configuration and its environment on the resulting properties of graphene remain poorly understood. These properties are important for electrical and catalytic applications of graphene. Thus, synthesizing specific configurations of nitrogen-doped graphene and consequently investigating the electrical and catalytic properties of the product is imperative. Herein, we demonstrate an approach that allows for successful production of nitrogen-functionalized RGO using Schiff base condensation between the amino groups in an o-aryl diamine compound and the carbonyl groups in GO. Three typical nitrogen-containing species including o-phenylenediamine (OPD), 2, 3-diaminopyridine (23DAP), and bis(trifluoromethyl)-1, 2-diaminobenzene (BTFMDAB) were used for functionalizing the GO samples, and the corresponding RGO derivatives (OPD-RGO, 23DAP-RGO, and BTF-RGO) were obtained by thermal annealing. Pyrazine nitrogen was successfully introduced into graphitic framework, as confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, thermal gravimetric analysis (TGA), Raman, and X-ray photoelectron spectroscopy (XPS). Field-effect transistors (FETs) based on the BTF-RGO exhibited hole-dominated ambipolar field-effect behavior with a Dirac point at a 9 V gate voltage and hole mobilities up to 2.5 times that of RGO. The weak p-type doping effect originated from the strongly electron-withdrawing trifluoromethyl groups. By studying the OPD-RGO and 23DAP-RGO-based FETs, containing pyrazine nitrogen and mixed pyrazine/pyridine nitrogen, respectively, we found that pyrazine nitrogen provided weak n-type doping effects, while pyridine nitrogen exhibited weak p-type doping effects due to its electron-withdrawing ability. Enhanced p-type doping effect was accompanied by the introduction of groups with stronger electron-withdrawing ability into the graphitic framework. Impressively, pyridine nitrogen in the pyrazine nitrogen-doped RGO yielded a weak p-type doped graphene due to the electron-withdrawing effect of the pyridine nitrogen. Nitrogen-doped graphene can be finely tuned from weak n-type to weak p-type doping by adjusting the electron-withdrawing ability of o-aryl diamine compounds. This study demonstrates the effect of nitrogen configuration and its surrounding environment on the electrical properties of RGOs, providing additional possible applications.     

Hexaazatriphenylene-Based Two-Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm⁻¹ after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate.     

Highly efficient modulation of the electronic properties of organic semiconductors by surface doping with 2D molecular crystals

Doping is a critically important strategy to modulate the properties of organic semiconductors(OSCs) to improve their optoelectrical performances. Conventional bulk doping involves the incorporation of foreign molecular species(i.e., dopants) into the lattice of the host OSCs, and thus disrupts the packing of the host OSCs and induces structural defects, which tends to reduce the mobility and(or) the on/off ratio in organic field-effect transistors(OFETs). In this article, we report a highly efficient and highly controllable surface doping strategy utilizing 2D molecular crystals(2DMCs) as dopants to boost the mobility and to modulate the threshold voltage of OFETs. The amount of dopants, i.e., the thickness of the 2DMCs, is controlled at monolayer precision, enabling fine tuning of the electrical properties of the OSCs at unprecedented accuracy. As a result, a prominent increase of the average mobility from 1.31 to 4.71 cm~2 V~(-1) s~(-1) and a substantial reduction of the threshold voltage from -18.5 to -1.8 V are observed. Meanwhile, high on/off ratios of up to 10~8 are retained.     

Doping Limits and Growth Thermodynamics of GaSb Crystals

Beside four approaches to the thermodynamics of GaSb-M(=S, Te) solid solutions the doping limits for extremely narrow concentration regions are analysed and ranked in the Cu, Ge, Mn (p-dopants), S, Se, Te (n-dopants) and N, In (isoelectric) groups. This revised version was published online in August 2006 with corrections to the Cover Date.     

改善高氯卤化银乳剂的高照度性能

本实验制备了高氯卤化银立方体系列乳剂和高氯卤化银(100)晶面T颗粒乳剂,对高氯卤化银立方体乳剂进行了不同种类掺杂剂的掺杂试验.通过测定以上各乳剂在常规曝光和高照度曝光下的照相性能,表明了在高氯卤化银乳剂中掺杂碘化物、掺杂铱络合物和掺杂浅电子陷阱掺杂剂都可以不同程度地改善乳剂的高照度性能,几种改进措施的结合效果更好.     

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.     

Electronic Characteristics of Perylene Diimide Anion Radical and Dianion Films by Quantitative Doping

Due to their unique physicochemical properties, the anion radical and dianion of perylene diimide derivatives(PDIs) recently attracted significant attention for organic semiconductors. However, the impact of packing structure and the radical content for carrier transport in the solid state still need to be determined. Bringing the electron-withdrawing groups is an effective strategy for enabling π-π stacking distance. Here, bay-tetrachloro-substituted PDI(B-4Cl-PDI) anion radical and dianion films were fabricated quantitatively doped with N₂H₄·H₂O. The radical contents were quantitatively calculated by absorption spectra in different doping ratios. The X-ray powder diffraction patterns showed that the anion radical presented a crystalline structure, and dianion aggregates exhibited an amorphous structure. With precise manipulation of the radical content, the anion radical aggregates and dianion aggregates showed the maximum electrical conductivity value of 0.024 and 0.0018 S/cm, respectively. The experiment results show that doping level and aggregate structure play a crucial role in electronic transport properties.     

Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-type dopant for organic semiconductors and its application in highly efficient solid-state dye-sensitized solar cells

Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm(-2)). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.     

Electronic structure of oligoaniline doped by inorganic and organic acids

The electronic structure of doped‐oligoaniline with various dopants is investigated by means of DFT method. After doping by hydrochloric acid (HCl) and camphorsulfonic acid (HCSA), the alternation of bond‐lengths is decreased and the co‐planarity of adjacent aromatic rings is increased. The π‐conjugating effect is increased in the electronic nature of Ph‐N system because the electrons can be delocalized along the backbone of oligoaniline where the hydrogen bonds as a bridge transfer the electrons. The electronic structure of polaron and bipolaron conformation and their relative stability is discussed, indicating that the preferable conformation is dependant on various dopants. The calculation results reveal that there is a relatively stronger interaction between the organic dopant of HCSA and N atoms of PANI, and more charge transfer between PANI and HCSA is a reason for the fact that the conductivity of HCSA‐doped PANI is higher than that of HCl‐doped PANI. The doping mechanism is proposed based on the calculation results. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

稠环电子受体光伏材料

基于非富勒烯受体的有机太阳能电池是化学和材料领域的热点前沿之一,中国领跑这个热点前沿.中国学者在非富勒烯受体材料方面取得了一系列重要的创新成果.我们提出了"稠环电子受体(FREA)"这一新概念,构建了高性能稠环电子受体新体系,发明了明星分子ITIC.我们的原创性工作引起了国内外同行的广泛关注和跟进.目前,基于稠环电子受体的有机太阳能电池效率已达到13%~14%,超过富勒烯体系.ITIC等稠环电子受体的出现颠覆了富勒烯受体在有机太阳能电池领域的统治地位,开创了有机太阳能电池的非富勒烯时代.本文简要评述了我们在高性能稠环电子受体设计与器件应用中的研究进展,并展望稠环电子受体的未来发展.     

Synthesis and characterization of cross-conjugated cruciforms with varied functional groups

A series of novel oligo(p-phenylenes) (OPPs) derivatives with bisdiene side-chains are synthesized and fully characterized. These cruciforms are soluble in common organic solvents and show good thermal stability. Absorption and emission spectra are recorded to study the effect of different electron-withdrawing and electron-donating groups on photophysical properties. Powder XRD shows crystalline structures for all the cruciforms. Single crystal XRD studies show tight-packing along the planar bisdiene axis but significant twisting along phenylene units, which correlate the role of functionalization along the bisdiene axis in tuning the band gaps of the cruciforms.     

Air‐Stable n‐Type Thermoelectric Materials Enabled by Organic Diradicaloids

Air‐stable n‐type thermoelectric materials are recognized as an important and challenging topic in organic thermoelectrics (OTEs) because conventional n‐type OTE materials prepared by chemical doping are highly volatile upon exposure to air. Besides, doping efficiency and microstructure are hard to control with the incorporation of external dopants. We report herein the design and synthesis of unconventional n‐type OTE materials based on the diradicaloids 2DQQT‐S and 2DQQT‐Se, which are proved to be neutral single‐component organic conductors that exhibit an unprecedented air stability. Without external n‐doping, a pristine film of 2DQQT‐Se shows an electrical conductivity as high as 0.29 S cm^?1 delivering a power factor of 1.4 μW m^?1 K^?2. Under ambient conditions, no decay in electrical conductivity is observed for over 260 hours. This work demonstrates that diradicaloids are promising candidates for air‐stable and high‐performance OTE materials.     

Effective design of A-D-A small molecules for high performance organic solar cells via F atom substitution and thiophene bridge

Novel A-D-A-type small molecule donors employ thiophene bridge and F-substitution to improve the power conversion efficiency in organic solar cell.     

Improving the Catalytic Performance of the Hydrogen Evolution Reaction of α-MoB2 via Rational Doping by Transition Metal Elements

Abundant transition metal borides are emerging as promising electrochemical hydrogen evolution reaction (HER) catalysts which have a potential to substitute noble metals. Those containing graphene-like (flat) boron layers, such as α-MoB2, are particularly promising and their performance can be further enhanced via doping by the second metal. In order to understand intrinsic effect of doping and rationalize selection of dopants, we employ density functional theory (DFT) calculations to study substitutional doping of α-MoB₂ by transition metals as a route towards systematic improvement of intrinsic catalytic activity towards HER. We calculated thermodynamic stability of various transition metal elements to select metals which form a stable ternary phase with α-MoB₂. We inspected surface stability of dopants and assessed catalytic activity of doped surface through hydrogen binding free energy at various hydrogen coverages. We calculated the reaction barriers and pathways for the Tafel step of HER for the most promising dopants. The results highlight iron as the best dopant, simultaneously lowering the reaction barrier of the Tafel step while having suitable thermodynamic stability within MoB₂ lattice.