High-performance N-type Semiconductors Research Articles

Self-Assembly Behavior, Aggregation Structure, and the Charge Carrier Transport Properties of S-Heterocyclic Annulated Perylene Diimide Derivatives.

The construction of high-performance n-type semiconductors is crucial for the advancement of organic electronics. As an attractive n-type semiconductor, molecular systems based on perylene diimide derivatives (PDIs) have been extensively investigated over recent years. Owing to the fascinating aggregated structure and high performance, S-heterocyclic annulated PDIs (SPDIs) are receiving increasing attention. However, the relationship between the structure and the electrical properties of SPDIs has not been deeply revealed, restricting the progress of PDI-based organic electronics. Here, we developed two novel SPDIs with linear and dendronized substituents in the imide position, named linear SPDI and dendronized SPDI, respectively. A series of structural and property characterizations indicated that linear SPDI formed a long-range-ordered crystalline structure based on helical supramolecular columns, while dendronized SPDI, with longer alkyl side chains, formed a 3D-ordered crystalline structure at a low temperature, which transformed into a hexagonal columnar liquid crystal structure at a high temperature. Moreover, no significant charge carrier transport signal was examined for linear SPDI, while dendronized SPDI had a charge carrier mobility of 3.5 × 10-3 cm2 V-1 s-1 and 2.1 × 10-3 cm2 V-1 s-1 in the crystalline and liquid crystalline state, respectively. These findings highlight the importance of the structure-function relationship in PDIs, and also offer useful roadmaps for the design of high-performance organic electronics for down-to-earth applications.

(F5PhO)2-F16-SiPc as an air-stable, high-performance n-type semiconductor with poor cannabinoid sensing capabilities

(F5PhO)2-F16-SiPc is an air stable, n-type semiconductor for organic thin-film transistors (OTFTs), however the structural changes that enhance its stability likely cause its lack of response to cannabinoids in a sensor.

N-type conjugated polymer semiconductor materials based on Aza-BODIPY dye with Naphthodipyrrolopyrrole (NDP-AB)

So far, the charge carrier mobility as well as the stability of n-type semiconductors fall behind when compared to the p-type ones. Therefore, exploring high-performance n-type semiconductor materials plays a crucial role in the further development of organic field-effect transistors (OFETs) for industrial applications. Naphthodipyrrolopyrrole-based dimeric aza-boron dipyrromethene dyes (NDP-AB) present strong electron-deficient units, which are rarely investigated. In this work, the NDP-AB chromophore is, for the first time, introduced as the acceptor in donor-acceptor type polymers. The results show that the NDP-AB based polymers exhibit extra-low LUMO energy levels, which endow the semiconductor layer with the ability to form Ohmic contacts with electrodes. This is advantageous for electron injection. In addition, the polymers present not only a strong aggregation as well as short π-π stacking d-spacing, but also a good planar polymer backbone and strong ICT effect. That phenomenon is advantage for the electron carrier transport across the adjacent molecules and the individual molecule. As a consequence, the NDP-AB-based polymers exhibit n-type behavior with electron transport mobility up to 0.89 cm2 V−1 s−1. This work demonstrate that NDP-AB is a promising electron-deficient building block for high-performance n-type semiconductors.

Isoindigo-based aza-BODIPY small molecule for N-type organic field-effect transistors

To date, most of the reported conjugated materials are p-type semiconductors, while the advances in n-type or ambipolar conjugated materials greatly fall behind those in p-type counterparts. Well-defined n-type semiconductors should possess suitable electron-deficient groups and relatively low lowest unoccupied molecular orbitals (LUMO) levels that facilitate the electron injection and stabilize the electron transport. Thus, developing novel n-type semiconductor materials with strong electron-deficient property, high electron mobility, and competitive stability is still highly desirable, though challenging. Herein, a new isoindigo-based dimeric aza-boron dipyrromethene (aza-BODIPY) chromophore (IIDG-AB) is designed and synthesized. IIDG-AB contains multiple fluorine and unsaturated nitrogen atoms, which endow it with strong electron-deficient property as well as an ultra-low LUMO level of only −4.24 eV. In addition, IIDG-AB features a large conjugation system and a high degree of coplanarity, which are beneficial for effective intermolecular charge transfer. The UV/visible absorption spectra, X-ray diffraction analysis, and morphological studies via atomic force microscopy imaging indicate that the IIDG-AB thin film presents strong aggregation, good π-π stacking, and long-range order packing, all of which are favorable for the electron transfer between neighboring molecules. Furthermore, IIDG-AB-based organic field-effect transistors exhibit a moderate stable n-type behavior with the highest electron mobility of 1.1 × 10−1 cm2 V−1 s−1. This work provides a simple and effective strategy to synthesize highly functional n-type chromophores via a Schiff base reaction between bislactams and heteroaromatic amines, and also paves the way for future design to fabricate high-performance n-type semiconductor materials for a wide range of applications.

A co-crystallization strategy toward high-performance n-type organic semiconductors through charge transport switching from p-type planar azaacene derivatives

The co-crystallization strategy has offered an efficient route to achieve high-performance n-type semiconductors through charge-transport switching from pristine p-type azaacene derivatives.

High-Performance All-Polymer Solar Cells Enabled by an n-Type Polymer Based on a Fluorinated Imide-Functionalized Arene.

A novel imide-functionalized arene, di(fluorothienyl)thienothiophene diimide (f-FBTI2), featuring a fused backbone functionalized with electron-withdrawing F atoms, is designed, and the synthetic challenges associated with highly electron-deficient fluorinated imide are overcome. The incorporation of f-FBTI2 into polymer affords a high-performance n-type semiconductor f-FBTI2-T, which shows a reduced bandgap and lower-lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analog without F or with F-functionalization on the donor moiety. These optoelectronic properties reflect the distinctive advantages of fluorination of electron-deficient acceptors, yielding "stronger acceptors," which are desirable for n-type polymers. When used as a polymer acceptor in all-polymer solar cells, an excellent power conversion efficiency of 8.1% is achieved without any solvent additive or thermal treatment, which is the highest value reported for all-polymer solar cells except well-studied naphthalene diimide and perylene diimide-based n-type polymers. In addition, the solar cells show an energy loss of 0.53 eV, the smallest value reported to date for all-polymer solar cells with efficiency > 8%. These results demonstrate that fluorination of imide-functionalized arenes offers an effective approach for developing new electron-deficient building blocks with improved optoelectronic properties, and the emergence of f-FBTI2 will change the scenario in terms of developing n-type polymers for high-performance all-polymer solar cells.

Imide-Modified Dinaphtho[1,2-b:2',1'-d]thiophene and Dinaphtho[1,2-b:2',1'-d]thiophene 13,13-Dioxide: Synthesis and Optoelectronic Properties.

Dinaphthothiophene has been reported as a promising p-type semiconductor. The development of high-performance n-type semiconductors is highly desirable. The introduction of an imide group into polycyclic aromatic hydrocarbons can lower their LUMO levels to meet the basic requirement of n-type organic semiconductor materials. In this work, we have synthesized four imide-modified dinaphthothiophenes and dinaphthothiophenedioxides. Their optoelectronic properties have been investigated. Their low-lying LUMO levels make them potential n-type semiconductor candidates.

Bulk transport and contact limitation of MoS2 multilayer flake transistors untangled via temperature-dependent transport measurements

Rational use of novel high-performance semiconductors in field-effect transistors (FETs) requires exact knowledge of the dominating charge transport mechanisms. In particular, the distinction between contact- and semiconductor-limited transport is important in FETs with small channel lengths. Here, we analyze the relative contributions of contact limitation and intrinsic conductivity of FETs based on mechanically exfoliated multilayers of the high performance n-type semiconductor molybdenum disulfide (MoS2). Based on a lithography-free fabrication process, we realize FETs with room temperature mobility (μ) of up to 46.8 cm2/Vs and ION/IOFF ratio of up to 105. Using temperature- and bias-dependent charge transport measurements, we are able to show that the intrinsic bulk transport in the flake can be best described by a phonon-limited band transport model with a conductive bulk at room temperature that freezes out upon cooling of the sample. In addition, we notice an increase of μ by a factor of 2–5 when using a self-assembled monolayer (SAM)-modified SiO2/MoS2 interface. More importantly, we show that the choice of drain–source bias (VDS) is crucial when interpreting MoS2 transport measurements, while for large VDS the intrinsic semiconductor transport properties can be observed, a strong contact limitation appears at low VDS. Our combined measurements allow us to distinguish between the effect of bulk and semiconductor/dielectric interface transport and the effect of contact resistance on the electrical transport properties.

Characteristics and Durability of Vertical-Type Organic Light-Emitting Transistors Using Poly(2-methoxy-5-(2- ethyl hexyloxy)-1,4-phenylenevinylene) and Indenofluorenedione Derivatives.

PSS/MEH-PPV/IF-dione-F/AI (gate)/IF-dione-F/Al (source). The characteristics of the vertical organic light emitting transistors were investigated from the measurements of radiancevoltage characteristics and external quantum efficiency. Furthermore, air stability was studied from the measurements of characteristics, impedance spectroscopy and contact angle.

Development of Amorphous Carbon-Based Variable Optical Gap Semiconductor Materials

Amorphous carbon (a-C) based semiconductor materials with variable optical gap and high semiconductor properties could be successfully fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PeCVD) method using a mixed solution of tetramethylsilane (TES) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS) as a liquid source. The optical gap could be controlled by varying sizes and number of sp 2 clusters included in multi-phase structure of a-C by incorporating Si atoms. The resulting Si-doped a-C with 10 six-membered rings in sp 2 clusters shows 1.76 eV of optical gap and Si-doped a-C with 4 six-membered rings in sp 2 clusters shows 2.76 eV. From photocurrent measurement under UV exposure, it was clarified that these films functioned as high performance n-type semiconductors with ca. 4 % of quantum yield, which was on the same level as that obtained at anatase-type titanium oxide prepared by the sol-gel method.

Trifluoromethyltriphenodioxazine: Air-Stable and High-Performance n-Type Semiconductor

Two trifluoromethyltriphenodioxazines were efficiently synthesized as active materials for n-type organic field-effect transistors, and their optical and electrochemical properties were characterized. Air-stable and high-performance thin film transistors based on the two compounds were fabricated.