Promising N-type Semiconductor Research Articles

Cyclobuteno[60]fullerenes as Efficient n-Type Organic Semiconductors.

Cyclobuteno[3,4:1,2][60]fullerenes have been prepared in a straightforward manner by a simple reaction between [60]fullerene and readily available allenoates or alkynoates as organic reagents under basic and mild conditions. The chemical structure of the new modified fullerenes has been determined by standard spectroscopic techniques and confirmed by X-ray diffraction analysis. Some of these new fullerene derivatives exhibit a remarkable intrinsic electron mobility (determined by using flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements), which surpasses that of the well-known phenyl-C61-butyric acid methyl ester, thus behaving as promising n-type organic semiconductors.

Synthesis of pyrrolidinofullerenes and their applications as an n-type component in organic transistors and polymer solar cells

We synthesized pyrrolidinofullerenes functionalized with an electron donor or acceptor group via Prato reaction. Their structures were studied using 1H-NMR, FT-IR and MALDI-TOF mass spectrometry. The electronic energy levels were calculated using quantum chemical calculation based on the density functional theory, showing that the lowest unoccupied molecular orbitals were in the range of −3.7 and −3.9 eV. The electron mobility of one of the fullerene derivatives was as high as 0.05 cm2/(V s), suggesting that pyrrolidinofullerenes can be promising n-type semiconductors. The fullerene derivatives were also blended with P3HT to fabricate bulk heterojunction polymer solar cells, and the performance of solar cells as a function of structural variations of the fullerene derivatives was investigated.

Perovskite Solar Cells Based on Low-Temperature Processed Indium Oxide Electron Selective Layers.

Indium oxide (In2O3) as a promising n-type semiconductor material has been widely employed in optoelectronic applications. In this work, we applied low-temperature solution-processed In2O3 nanocrystalline film as an electron selective layer (ESL) in perovskite solar cells (PSCs) for the first time. By taking advantages of good optical and electrical properties of In2O3 such as high mobility, wide band gap, and high transmittance, we obtained In2O3-based PSCs with a good efficiency exceeding 13% after optimizing the concentration of the precursor solution and the annealing temperature. Furthermore, to enhance the performance of the In2O3-based PSCs, a phenyl-C61-butyric acid methyl ester (PCBM) layer was introduced to modify the surface of the In2O3 film. The PCBM film could fill up the pinholes or cracks along In2O3 grain boundaries to passivate the defects and make the ESL extremely compact and uniform, which is conducive to suppressing the charge recombination. As a result, the efficiency of the In2O3-based PSC was improved to 14.83% accompanied with V(OC), J(SC), and FF being 1.08 V, 20.06 mA cm(-2), and 0.685, respectively.

Dealloying of Few Coating: From Disorder to Order

Oxide semiconductors are widely used as photocatalysts in environmental purification as well as energy harvesting and transformation. Thanks to its narrow energy band gap, WO3 (2.7eV) and Fe2O3 (2.2eV) is recognized as one of the most promising n-type semiconductors resistant to photocorrosion in acidic and alkaline aqueous solution respectively, and shows interesting properties both in visible light absorption and its good charge transport abilities. To pursue higher quantum efficiency, nanostructures are a favorable choice, many WO3 and Fe2O3 nanostructures in the form of powders, nanowires, nanorods, nanobelts and nanochannels have been synthesized and reported. Precisely controlled conditions and complicated fabrication methods have been needed in the preparation of WO3 and Fe2O3-based photocatalysts for water decomposition. Dealloying was considered to be a simple, mild and economical method to fabricate nanostructures, such as nanoporous structures, nanowires, nanocages, etc. As determined by their chemical potentials, the more active (less noble) component is selectively dissolved, while the other phase represents simultaneously a self-assembling action, which is controlled by atom diffusion and the materials’ intrinsic properties. In this work, we propose a more facile and efficient way to nanostructures by dealloying the as-electrodeposited FeW amorphous alloy coating in an acidic and alkaline environments. It was found that highly ordered WO3 and Fe2O3nanoflake arrays were successfully synthesized and remarkable photoelectrochemical performance in water splitting of the novel nanostructure photoanode can be achieved by this disorder to order transformation.

The effect of perylene diimides chemical structure on the photovoltaic performance of P3HT/perylene diimides solar cells

Core substituted perylene diimides are promising n-type semiconductor materials for organic photovoltaic applications. We have prepared three Donor-Acceptor-Donor perylene diimide molecules, substituted in bay positions with bithiophene, spirobifluorene and bithiophene spirobifluorene groups. These molecules were tested as electron acceptors, in blend with P3HT as donor material, in bulk heterojunction solar cells. The active layers of these devices were optimized by thermal treatment or by the presence of additives and the photovoltaic characteristics were measured. The photovoltaic performances of the three perylene diimides were studied and discussed through absorption and emission spectroscopy characterization, atomic force microscopy morphology study and charge-carrier transport measurements.

Influence of precursor concentration on the structural, optical and electrical properties of indium oxide thin film prepared by a sol–gel method

This research was carried out to study the effect of different precursor concentrations on the physical properties of indium oxide (In2O3) thin film. In2O3 is a promising n-type semiconductor material that has been used in optoelectronic applications because of its highly transparent properties. It is a transparent conducting oxide with a wide band gap (∼3.7eV). The experiment was started by preparing different precursor concentrations of indium nitrate hydrate (In (NO3)·H2O) solution and followed by the spin coating technique prior to an annealing process at 500°C. Indium oxide thin films were characterized using an X-ray diffractometer, an ultraviolet–visible spectroscopy, a field emission scanning electron microscope and a Hall Effect Measurement System in order to determine the influence caused by the different molarities of indium oxide. The result showed that the film thickness increased with the indium oxide molarity. Film thicknesses were in the range of 0.3–135.1nm and optical transparency of films was over 94%. Lowest resistivity of 2.52Ωcm with a mobility of 26.60cm2V−1S−1 and carrier concentration of 4.27×1017cm−3 was observed for the indium oxide thin film prepared at 0.30M.

Toward electron-deficient pyrene derivatives: construction of pyrene tetracarboxylic diimide containing five-membered imide rings.

Electron-deficient pyrene-1,2,6,7-tetracarboxylic diimide () and its cyano derivative () have been designed and synthesized as a new family of aromatic diimides. PyrDI has two unexpected five-membered imide rings and can form excimers facilely in the solid state. These new pyrene derivatives are promising n-type semiconductors for organic electronics.

Bioinspired Nanoarchitectonics of Naphthalene Diimide to Access 2D Sheets of Tunable Size, Shape, and Optoelectronic Properties

A bioinspired nanoarchitectonics design strategy is adapted to construct 2D sheets of promising n-type organic semiconductor naphthalene diimide (NDI) with tunable size, shape and optoelectronic properties. Modulation of noncovalent interactions such as intermolecular NDI–NDI aromatic and hydrogen bonding interactions among the molecules within the self-assembled 2D sheets is achieved by the minute structural mutations on the NDI imide substitutions in the form of glycine derivatives (carboxylic acid, amide and ester). Microscopy studies (FESEM and AFM) showed the formation of flat, smooth and large 2D nanosheets with distinct lateral and height profiles. Photophysical studies revealed unique solid state optoelectronic properties with promising temperature responsive fluorescence behavior with quite longer life time values which are useful as temperature sensor materials. The concentration and temperature dependent 1H NMR and IR studies provided the insights into distinct noncovalent interactions responsible for the observed NDI 2D sheets with variable size and shape. Furthermore, PXRD studies revealed highly crystalline molecular organization within the 2D sheets. On account of these tunable unique properties, the 2D sheets derived from NDI-conjugates might find a wide range of future interdisciplinary applications from materials to biomedicine.

Colloidal synthesis and characterization of Bi2S3 nanoparticles for photovoltaic applications

Bismuth sulfide is a promising n-type semiconductor for solar energy conversion. We have explored the colloidal synthesis of Bi2S3 nanocrystals, with the aim of employing them in the fabrication of solution-processable solar cells and to replace toxic heavy metals chalcogenides like PbS or CdS, that are currently employed in such devices. We compare different methods to obtain Bi2S3 colloidal quantum dots, including the use of environmentally benign reactants, through organometallic synthesis. Different sizes and shapes were obtained according to the synthesis parameters and the growth process has been rationalized by comparing the predicted morphology with systematic physical-chemistry characterization of nanocrystals by X-ray diffraction, FT-IR spectroscopy, Transmission Electron Microscopy (TEM).

Self-directed orientation of molecular columns based on n-type hexaazatrinaphthylenes (HATNAs) for electron transport.

Self-organizing n-type hexaazatrinaphthylenes (HATNAs) with various bay-located side chains have been synthesized. The HATNA derivatives are able to form long-range molecular columns with self-directed growth directions. In particular, alkyl-substituted HATNAs showed in-plane molecular columns with axes parallel to substrates, whereas the columnar orientation of the HATNAs with alkylethynyl or alkylthio groups strongly depended on the length of the introduced side chains. Interestingly, the derivative with octylthio chains exhibited out-of-plane molecular columns, in which electron mobility of up to 10(-3) cm(2) V(-1) s(-1) was determined through the time-of-flight technique, highlighting the fact that such molecular columns based on bay-substituted HATNAs are promising n-type semiconductors for device applications.

Affection of Post-Nitrogen-Doping of ZnO Columnar Films Photo-Anode on Performance of Dye-Sensitized Solar Cells

ZnO was a promising n-type conductive semiconductor material for dye-sensitized solar cells. Stable and efficient preparation of high quality p-type ZnO films became the main difficulty in current research. In this paper, a nitrogen-doped ZnO columnar film on an indium tin oxide (ITO) substrate was successfully obtained by gas phase method. The absorption of visible light was improved by nitrogen-doped ZnO columnar films. This experiment provided a good strategy for the full utilization of solar energy.

Photoluminescent n-type liquid organic semiconductor

Liquid 4,7-bis(1-decynl)-2,1,3-benzothiadiazole (DOBT) is found to exhibit good photoluminescence (PL) with high PL efficiency up to 17.8%. In particular, DOBT shows electron mobility of 5.2×10-6 cm2V-1s-1, demonstrating a promising n-type liquid semiconductor for optoelectronic application.

Room temperature fabricated flexible NiO/IGZO pn diode under mechanical strain

Flexible electronic devices fabricated on plastic substrates require semiconductors, which can be deposited at low temperatures. While Indium–Gallium–Zinc-Oxide (IGZO) is a promising n-type oxide semiconductor, a p-type oxide semiconductor with similar performance is currently not available. Here, the room temperature deposition of nickel oxide (NiO) acting as a p-type oxide semiconductor on a flexible plastic foil is described. NiO exhibits a carrier density of+1.6×1017cm−3 and a Hall mobility of 0.45cm2/Vs. p-type NiO is combined with n-type IGZO to fabricate flexible pn diodes on a free-standing polyimide substrate. The diodes show an ideality factor of ≈3.2 and an on–off current-ratio of ≈104. The NiO/IGZO diodes stay fully operational when exposed to tensile or compressive mechanical strain of 0.25%, induced by bending to a radius of 10mm. In addition, a 50Hz AC signal was rectified using a flexible diode while flat and bent.

Contact printing of horizontally aligned Zn2GeO4and In2Ge2O7nanowire arrays for multi-channel field-effect transistors and their photoresponse performances

The ternary oxides, Zn2GeO4 and In2Ge2O7 nanowires, are promising n-type semiconductors with outstanding transport properties for high performance electronic devices. By using the direct contact printing process, we reported the assembly of horizontally aligned Zn2GeO4 and In2Ge2O7 nanowire arrays to be used as building blocks for high performance multi-channel field-effect transistors. The as-fabricated multi-channel transistors exhibited higher voltage stability and repeatability than their single nanowire based counterparts. The effective mobilities of the multi-channel field-effect transistors were calculated to be 25.44 cm2 V−1 s−1 and 11.9 cm2 V−1 s−1, comparable to the single-channel FETs. The as-fabricated multi-channel transistors were also used as high performance photodetectors, exhibited a high sensitivity to ultraviolet light illumination with a photoconductive gain and quantum efficiency as high as 1.034 × 105 and 1.032 × 107% for Zn2GeO4 nanowires and 2.58 × 105 and 2.617 × 107% for In2Ge2O7 nanowires.

Addressing the use of PDIF-CN2 molecules in the development of n-type organic field-effect transistors for biosensing applications

BackgroundThere is no doubt that future discoveries in the field of biochemistry will depend on the implementation of novel biosensing techniques, able to record biophysiological events with minimal biological interference. In this respect, organic electronics may represent an important new tool for the analysis of structures ranging from single molecules up to cellular events. Specifically, organic field-effect transistors (OFET) are potentially powerful devices for the real-time detection/transduction of bio-signals. Despite this interest, up to date, the experimental data useful to support the development of OFET-based biosensors are still few and, in particular, n-type (electron-transporting) devices, being fundamental to develop highly-performing circuits, have been scarcely investigated. MethodsHere, films of N,N′-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2) molecules, a recently-introduced and very promising n-type semiconductor, have been evaporated on glass and silicon dioxide substrates to test the biocompatibility of this compound and its capability to stay electrically-active even in liquid environments. ResultsWe found that PDIF-CN2 transistors can work steadily in water for several hours. Biocompatibility tests, based on in-vitro cell cultivation, remark the need to functionalize the PDIF-CN2 hydrophobic surface by extra-coating layers (i.e. poly-l-lysine) to favor the growth of confluent cellular populations. ConclusionsOur experimental data demonstrate that PDIF-CN2 compound is an interesting organic semiconductor to develop electronic devices to be used in the biological field. General significanceThis work contributes to define a possible strategy for the fabrication of low-cost and flexible biosensors, based on complex organic complementary metal-oxide-semiconductor (CMOS) circuitry including both p- (hole-transporting) and n-type transistors. This article is part of a Special Issue entitled Organic Bioelectronics—Novel Applications in Biomedicine.

Developing perylene diimide based acceptor polymers for organic photovoltaics

Perylene diimides are known as promising n-type semiconductor building blocks. Here we report the synthesis and characterization of a set of three soluble poly(perylene diimide)s and their preliminary characterization in organic photovoltaic cells. These polymers are made through the polycondensation of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) with a variety of poly(ethylene glycol) (PEG)- or poly(propylene glycol) (PPG)-based diamine comonomers. The flexible spacer offers increased solubility in organic solvents and allows the perylene core to assume a conformation that promotes favorable cofacial π–π interactions. Mixtures of these polymers with the hole-transporting polymer, poly(3-hexylthiophene) (P3HT) result in significant fluorescence quenching. However, the phase separation occurs on a scale too large for a bulk heterojunction solar cell. The PPGylated poly(perylene diimide) shows an unusually low free electron concentration (∼1.0 × 10 12 cm −3) and therefore makes an excellent model system for future doping studies. These new polymers may have promise as stable electron-conductive layers with large light-absorptivities in solution-processable applications of organic electronics.

Solution Processable n-Type Perylene Diimide Copolymers for Organic Photovoltaics

ABSTRACTPerylene diimides are known as promising n-type semiconductor building blocks. Here we report the synthesis and characterization of a set of three soluble poly(perylene diimide)s and their preliminary characterization in organic photovoltaic cells. These polymers are made through the polycondensation of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) with a variety of poly(ethylene glycol) (PEG)- or poly(propylene glycol) (PPG)-based diamine comonomers. The flexible spacer offers increased solubility in organic solvents and allows the perylene core to assume a conformation that promotes favorable cofacial π–π interactions. Mixtures of these polymers with the hole-transporting polymer, poly(3-hexylthiophene) (P3HT) result in significant fluorescence quenching. However, the phase separation occurs on a scale too large for a bulk heterojunction solar cell. The PPGylated poly(perylene diimide) shows an unusually low free electron concentration (~1.0 × 1012 cm-3) and therefore makes an excellent model system for future doping studies. These new polymers may have promise as stable electron-conductive layers with large light-absorptivities in solution-processable applications of organic electronics.

Synthesis and electronic properties of pentacene derivatives as promising n-type semiconductor candidates

Abstract Two pentacene derivatives 1 and 2 were synthesized from the Diels-Alder reactions of furan derivatives with 1,4-benzoquinone. They were characterized by the methods of 1H — nuclear magnetic resonance spectroscopy (1H-NMR), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), ultraviolet and visible spectrophotometry (UV-VIS), photoluminescence (PL) spectrometry and cyclic voltammetry (CV). The energy gaps of 1 and 2, taken directly from spectroscopic measurements, are broad as 2.72 and 2.46 eV, leading to blue and greenish blue photoluminescence, respectively. The LUMO and HOMO energy levels are −2.77 and −5.49 eV for 1, and −2.91 and −5.37 eV for 2, respectively. The low energy levels make both 1 and 2 good air-stabilities and promising n-type semiconductor candidates for use in organic electronics.

N-Type Conjugated Dendrimers: Convergent Synthesis, Photophysics, Electroluminescence, and Use as Electron-Transport Materials for Light-Emitting Diodes

Three new electron-acceptor and light-emitting conjugated dendrimers, [G1-4Q], [G1-6Q], and [G2-12Q], based on a benzene core, poly(phenylenevinylene) dendrons, and diphenylquinoline peripheral groups have been synthesized, characterized, and used as emissive and electron-transport materials in efficient light-emitting diodes. All three dendrimers emit blue light (λmax = 414 nm) in solution with high fluorescence quantum yields in the 0.69−0.87 range and fluorescence lifetimes of 1.4−1.6 ns. In thin films the dendrimers emit yellow light with poor fluorescence efficiency, suggesting aggregation and excimer formation in the solid state. The dendrimers showed quasi-reversible electrochemical reduction with a formal potential of −2.0 V (vs SCE) and derived LUMO levels of 2.5−2.6 eV, implying that injected electrons are localized in the periphery of the dendrimers. As the emissive materials in light-emitting diodes, the dendrimers showed yellow electroluminescence the brightness and efficiency of which increased with generation and number of electron-acceptor peripheral groups. The performance of bilayer light-emitting diodes using the dendrimers as the electron-transport layers and poly(2-methoxy-5-(2‘-ethyl-hexyloxy)-1,4-phenylene vinylene) as the emissive layer increased with generation and number of electron-acceptor peripheral groups, reaching a maximum external efficiency of 5.0%, a power efficiency of 1.3 lm/W, and a brightness of up to 2000 cd/m2 in ambient air using aluminum cathode. These results demonstrate that electron-acceptor and electron-transport dendrimers can be created by functionalization of the dendrimer periphery. The new dendrimers are promising n-type semiconductors for organic electronic and optoelectronic devices.

New n-type organic semiconductors: synthesis, single crystal structures, cyclic voltammetry, photophysics, electron transport, and electroluminescence of a series of diphenylanthrazolines.

The synthesis, properties, and electroluminescent device applications of a series of five new diphenylanthrazoline molecules 1a-1e are reported. Compounds 1b, 1c, and 1d crystallized in the monoclinic system with the space groups P2(1)/c, C2/c, and P2(1)/c, respectively, revealing highly planar molecules. Diphenylanthrazolines 1a-1e have a formal reduction potential in the range -1.39 to -1.58 V (versus SCE) and estimated electron affinities (LUMO levels) of 2.90-3.10 eV. Compounds 1a-1e emit blue light with fluorescence quantum yields of 58-76% in dilute solution, whereas they emit yellow-green light as thin films. The diphenylanthrazoline molecules as the emissive layers in light-emitting diodes gave yellow light with a maximum brightness of 133 cd/m(2) and an external quantum efficiency of up to 0.07% in ambient air. Bilayer light-emitting diodes using compounds 1a-1e as the electron-transport layer and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) as the emissive layer had a maximum external efficiency of 3.1% and 2.0 lm/W and a brightness of up to 965 cd/m(2) in ambient air. These results represent enhancements of up to 50 times in external quantum efficiency and 17 times in brightness when using 1a-1e as the electron-transport materials in polymer light-emitting diodes. These results demonstrate that the new diphenylanthrazolines are promising n-type semiconductors for organic electronics.