Asymmetric side-chain engineering of organic semiconductor for ultrasensitive gas sensing

Molecular structure of organic semiconductor plays a critical role in determining the performance and functionality of organic electronic devices,by optimizing the electrical,optical and physicochemical properties.Substituted alkyl chains are fundamental units in tailering the solubility and assemblability,among which the asymmetric properties have been reported as key element for controlling the packing motifs and intrinsic charge transport.Here,we expanded the scope of molecular asymmetry dependent sensing features based on a new series of naphthalene diimides(NDI)-based derivatives substituted with a same branching alkyl chain but various linear-shaped alkyl chains(Cn-).A clear molecular stacking change,from head-to-head bilayer to head-to-tail monolayer packing model,is observed based on the features of anisotropic molecular interactions with the change in the chain length.Most importantly,a unique LUMO level shift of 0.17 eV is validated for NDI-PhC4,providing a record sensitivity up to 150%to 0.01 ppb ammonia,due to the desired molecular reactivity and device amplification properties.These results indicate that asymmetric side-chain engineering opens a route for breath healthcare.

1,2,5,6-Naphthalene Diimides:A Class of Promising Building Blocks for Organic Semiconductors

Organic semiconductors have drawn extensive atten-tion due to their optoelectronic properties and wide applications in organic optoelectronics.In comparison with the popular 1,4,5,8-naphthalene diimides(1,4,5,8-NDIs),the angular-shaped 1,2,5,6-NDIs have exhibited tunable photophysical properties,self-as-sembly behaviors and charge transporting properties.Due to these unique features,1,2,5,6-NDIs show great potential for construction of high performance n-func-tional materials.In this review,we highlight the recent advances and future prospects of 1,2,5,6-NDI-basedπ-systems in the field of organic optoelectronics,in-cluding molecular design,synthesis,structure-prop-erty relationships as well as the applications in high performance organic field-effect transistors,organic photovoltaics,perovskite solar cells,and so on.

Benzothiophene and benzosulfone fused pyrazino[2,3-g]quinoxaline:Synthesis and semiconducting properties

A novel air-stable n-type benzothiaphene endcapped azaarene(BTPQ) and its sulfonated derivative(BSPQ) were prepared via two pathways and characterized by NMR, UV–vis, fluorescence and cyclic voltammetry spectroscopy. Symmetrically introducing four nitrogen atoms into acenes, the semiconductor properties could be changed from p-type to n-type detected through the space charge limited current(SCLC) method. After sulfonation of BTPQ, BSPQ is with deeper frontier orbital energy levels and enhanced the electron mobility.

High mobility organic semiconductors for field-effect transistors

Organic field-effect transistors(OFETs) are attracting more and more attention due to their potential applications in low-cost, large-area and flexible electronic products. Organic semiconductors(OSCs) are the key components of OFETs and basically determine the device performance. The past five years have witnessed great progress of OSCs. OSCs used for OFETs have made rapid progress, with field-effect mobility much larger than that of amorphous silicon(0.5?1.0 cm2/(V s)) and of up to 10 cm2/(V s) or even higher. In this review, we demonstrate the latest progress of OSCs for OFETs, where more than 50 representative OSCs are highlighted and analyzed to give some valuable insights for this important but challenging field.

New Core-Expanded Naphthalene Diimides for n-Channel Organic Thin Film Transistors

膨胀核心的萘 diimides 的四个班(1a， 1b， 2a， 2b， 3 和 4 ) 那头熊不同的电子缺乏的硫 heterocycles 被设计并且综合。1a 的处理答案的薄电影， 2a， 3 和 4 作为 n 隧道在空中操作了很好有电子活动性从 106 ～ 0.14 cm2/Vs 的器官的晶体管，取决于不同结合的脊梁。薄电影微观结构研究也被执行为 1a 的薄电影理解电子活动性的变化， 2a， 3 和 4。

n-Channel Organic Transistors Processed from Halogen-Free Solvents： Solvent Effect on Thin-Film Morphology and Charge Transport

Non-chlorinated solvents are highly preferable for organic electronic processing due to their environmentally friendly characteristics. Four different halogen-free solvents, tetrafuran, toluene, meta-xylene and 1,2,4-trimethyl- benzene, were selected to fabricate n-channel organic thin film transistors （OTFTs） based on 3-hexylundecyl sub- stituted naphthalene diimides fused with （1,3-dithiol-2-ylidene）malononitrile groups （NDI3HU-DTYM2）. The OTFTs based on NDI3HU-DTYM2 showed electron mobility of up to 1.37 cm2-V-1·s -1 under ambient condition. This is among the highest device performance for n-channel OTFTs processed from halogen-free solvents. The dif- ferent thin-film morphologies, from featureless low crystalline morphology to well-aligned nanofibres, have a great effect on the device performance. These results might shed some light on solvent selection and the resulting solution process for organic electronic devices.

Extremely simple phenothiazine molecules with room-temperature phosphorescence for understanding mechanoluminescence excitation process

Mechanoluminescence(ML)is a light-emitting process induced by mechanical stimuli and has attracted ever increasing attention due to its potential applications in displays,lighting,bio-imaging and pressure sensing[1,2].On the other hand,room-temperature phosphorescent(RTP)materials are attractive because of their multidisciplinary applications in electronics,optics,and biological areas[3].The development of organic ML luminogens with RTP properties is very important but extremely challenging because of a lack of reliable guidance,the unclear

Azulenoisoindigo: A building block for π-functional materials with reversible redox behavior and proton responsiveness

Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, azulenoisoindigo(Az II), an azulene-based isoindigo analogue, is designed and synthesized, which has a twisted molecular backbone and R/Sisomers in single crystals. Interestingly, Az II shows the characteristics of both isoindigo and azulene,such as reversible redox behavior and reversible proton responsiveness. UV-vis-NIR,^(1)H NMR and electron paramagnetic resonance(EPR) measurements were carried out to get insights into the possible mechanism of the proton-responsive property of Az II. The results demonstrated that only one azulenyl moiety of molecule of Az II was protonated and deprotonated, and the protonated Az II can be further oxidized to form azulenium cation radicals.

Largeπ-extended donor-acceptor polymers for highly efficient in vivo near-infrared photoacoustic imaging and photothermal tumor therapy

Semiconducting polymers(SPs)with intensive near-infrared(NIR)absorption and high photothermal conversion efficiencies have been employed as a new generation of photothermal agents(PTAs)for“all-in-one”theranostic nanoplatforms with integrated photoacoustic imaging(PAI)and photothermal therapy(PTT)functions.However,the lack of facile molecular design principles impedes the development of highly efficient NIR PTAs.Herein,a facile molecular design strategy based on largeπ-extended donor-acceptor(L-π-D-A)structure is reported for achieving SPs(SP1-SP3)with highly efficient in vitro and in vivo PAI and PTT capabilities.Through adjusting the conjugation length and planarity of the donor units,both SP3 and corresponding nanoparticle(SPN)SPN3 exhibit stronger D-A strength,intensive NIR absorption,enhanced absorption coefficient,and higher photothermal conversion efficiency(up to 61.8%).The excellent photothermal conversion efficiencies make SPN1-SPN3 produce efficient inhibition of tumor growth with excellent biocompatibility and prominent PAI performance with a high contrast manner in living mice at a low systemic injection mass.Our research highlights that the new L-π-D-A molecular design is an effective strategy to obtain highly efficient polymeric NIR PTAs for high desirable cancer phototheranostic nanoplatforms.

Selenium-containing core-expanded naphthalene diimides for high performance n-type organic semiconductors

The incorporation of heavy atoms into molecular backbone is an extremely straightforward strategy for fine-tuning the optoelectronic properties of organic semiconductors.However,it is rarely studied in n-type small molecules.Herein,by selenium substitution of NDI3 HU-DTYM2,two Se-decorated core-expanded naphthalene diimides(NDI)derivatives DTYM-NDI3 HUDSYM(1)and NDI3 HU-DSYM2(2)were synthesized.In comparison with the reference S-containing compound NDI3 HUDTYM2,the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)energy levels of 1 and 2 were fine-tuned with?HOMO of about 0.2 e V,?LUMO of 0.1 e V and the narrowed HOMO-LUMO gaps.More surprisingly,the as-spun organic thin film transistors(OTFTs)based on 1 and 2 both showedμe,satvalues as high as1.0 cm2 V-1 s-1,which are 2-fold higher than that of NDI3 HU-DTYM2 with the same device structure and measurement conditions.In addition,the single crystal OFET devices based on Se-containing compound NDI2 BO-DSYM2 showed a highμe,satvalue of 1.30 cm2 V-1 s-1.The molecular packing of NDI2 BO-DSYM2 in single crystals(two-dimensional supramolecular structure formed by intermolecular Se···Se interactions)is quite different from that of a S-containing compound NDI-DTYM2(one dimensional supramolecular structure formed by intermolecularπ-πstacking).Therefore,the Se substitution can cause dramatic change about molecular stacking model,giving rise to high n-type OTFT performance.Our results demonstrated an effective strategy of the heavy atom effect for designing novel organic semiconductors.

Tuning the Charge Transport Property of Naphthalene Diimide Derivatives by Changing the Substituted Position of Fluorine Atom on Molecular Backbone

Three naphthalene diimides(2,3 and 4)fused with 2-(1,3-dithiol-2-ylidene)-2-fluorophenylacetonitrile moieties were designed and synthesized.Due to the different substituted positions of fluorine atom on the phenyl group,the solution-processed thin films of 2 and 3 operated in air as n-channel transistors,while the films of 4 performed as ambipolar transistors,indicating that the variation of substituted position of fluorine atom on molecular backbone may tune the material’s charge transport behavior.

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Organic thermoelectric(OTE)materials have gained widespread attention because of their potential for wearable power generators and solid cooling elements.Nevertheless,the development of state-ofthe-art OTE materials still suffers from limited molecular categories because of the rarity ofmolecular design strategies,which limits further development of this emerging field.Recently,many efforts have been devoted to developing molecular design concepts for high performance OTE materials.