Two-dimensional hole gas in organic semiconductors.

A highly conductive metallic gas that is quantum mechanically confined at a solid-state interface is an ideal platform to explore non-trivial electronic states that are otherwise inaccessible in bulk materials. Although two-dimensional electron gases have been realized in conventional semiconductor interfaces, examples of two-dimensional hole gases, the counterpart to the two-dimensional electron gas, are still limited. Here we report the observation of a two-dimensional hole gas in solution-processed organic semiconductors in conjunction with an electric double layer using ionic liquids.

Damage-free Metal Electrode Transfer to Monolayer Organic Single Crystalline Thin Films.

Solution-processed organic thin film transistors (OTFTs) are an essential building block for next-generation printed electronic devices. Organic semiconductors (OSCs) that can spontaneously form a molecular assembly play a vital role in the fabrication of OTFTs. OTFT fabrication processes consist of sequential deposition of functional layers, which inherently brings significant difficulties in realizing ideal properties because underlayers are likely to be damaged by application of subsequent layers.

A Large Anisotropic Enhancement of the Charge Carrier Mobility of Flexible Organic Transistors with Strain: A Hall Effect and Raman Study.

Utilizing the intrinsic mobility-strain relationship in semiconductors is critical for enabling strain engineering applications in high-performance flexible electronics. Here, measurements of Hall effect and Raman spectra of an organic semiconductor as a function of uniaxial mechanical strain are reported. This study reveals a very strong, anisotropic, and reversible modulation of the intrinsic (trap-free) charge carrier mobility of single-crystal rubrene transistors with strain, showing that the effective mobility of organic circuits can be enhanced by up to 100% with only 1% of compressive strain.

High-performance, semiconducting membrane composed of ultrathin, single-crystal organic semiconductors.

Thin film transistors (TFTs) are indispensable building blocks in any electronic device and play vital roles in switching, processing, and transmitting electronic information. TFT fabrication processes inherently require the sequential deposition of metal, semiconductor, and dielectric layers and so on, which makes it difficult to achieve reliable production of highly integrated devices. The integration issues are more apparent in organic TFTs (OTFTs), particularly for solution-processed organic semiconductors due to limits on which underlayers are compatible with the printing technologies.

Scalable Fabrication of Organic Single-Crystalline Wafers for Reproducible TFT Arrays.

Building on significant developments in materials science and printing technologies, organic semiconductors (OSCs) promise an ideal platform for the production of printed electronic circuits. However, whether their unique solution-processing capability can facilitate the reliable mass manufacture of integrated circuits with reasonable areal coverage, and to what extent mass production of solution-processed electronic devices would allow substantial reductions in manufacturing costs, remain controversial. In the present study, we successfully manufactured a 4-inch (c.

Efficient molecular doping of polymeric semiconductors driven by anion exchange.

The efficiency with which polymeric semiconductors can be chemically doped-and the charge carrier densities that can thereby be achieved-is determined primarily by the electrochemical redox potential between the π-conjugated polymer and the dopant species. Thus, matching the electron affinity of one with the ionization potential of the other can allow effective doping. Here we describe a different process-which we term 'anion exchange'-that might offer improved doping levels.

Wafer-scale, layer-controlled organic single crystals for high-speed circuit operation.

Two-dimensional (2D) layered semiconductors are a novel class of functional materials that are an ideal platform for electronic applications, where the whole electronic states are directly modified by external stimuli adjacent to their electronic channels. Scale-up of the areal coverage while maintaining homogeneous single crystals has been the relevant challenge. We demonstrate that wafer-size single crystals composed of an organic semiconductor bimolecular layer with an excellent mobility of 10 cm V s can be successfully formed via a simple one-shot solution process.

Boron-Stabilized Planar Neutral π-Radicals with Well-Balanced Ambipolar Charge-Transport Properties.

Organic neutral π-monoradicals are promising semiconductors with balanced ambipolar carrier-transport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(α) and SOMO(β), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits well-balanced ambipolar carrier transport properties.

Suppressing molecular vibrations in organic semiconductors by inducing strain.

Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors.

Transition between band and hopping transport in polymer field-effect transistors.

Hall effect and slightly negative temperature dependence of the mobility in polymeric transistors are demonstrated. The semiconductor channel is based on a polycyclopentadithiophene-benzothiadiazole (CDT-BTZ) donor-acceptor copolymer film whose chain direction is oriented by mechanical compression at the surface of an ionic liquid. The mobility is 5.

Polarization fatigue of organic ferroelectric capacitors.

The polarization of the ferroelectric polymer P(VDF-TrFE) decreases upon prolonged cycling. Understanding of this fatigue behavior is of great technological importance for the implementation of P(VDF-TrFE) in random-access memories. However, the origin of fatigue is still ambiguous.

High-performance solution-processable N-shaped organic semiconducting materials with stabilized crystal phase.

N-shaped organic semiconductors are synthesized via four steps from a readily available starting material. Such semiconductors exhibit preferable ionization potential for p-type operation, thermally stable crystalline phase over 200 °C, and high carrier mobility up to 16 cm(2) V(-1) s(-1) (12.1 cm(2) V(-1) s(-1) on average) with small threshold voltages in solution-crystallized field-effect transistors.