Organic semiconductor

About: Organic semiconductor is a research topic. Over the lifetime, 15905 publications have been published within this topic receiving 533881 citations.

Ambipolar Charge Transport in Air-Stable Polymer Blend Thin-Film Transistors

Abstract: Ambipolar thin-film transistors based on a series of air-stable, solution-processed blends of an n-type polymer poly(benzobisimidazobenzophenanthroline) (BBL) and a p-type small molecule, copper phthalocyanine (CuPc) are demonstrated, where all fabrication and measurements are performed under ambient conditions. The hole mobilities are in the range of 6.0 × 10–6 to 2.0 × 10–4 cm2 V–1 s–1 and electron mobilities are in the range of 2.0 × 10–6 to 3.0 × 10–5 cm2 V–1 s–1, depending on the blend composition. UV-vis spectroscopy and electron diffraction show crystallization of CuPc in the metastable α-crystal form within the semicrystalline BBL matrix. These CuPc domains develop into elongated ribbon-like crystalline nanostructures when the blend films are processed in methanol, but not when they are processed in water. On methylene chloride vapor annealing of the blend films, a phase transformation of CuPc from the α-form to the β-form is observed, as shown by optical absorption spectroscopy and electron diffraction. Ambipolar charge transport is only observed in the blend films where CuPc crystallized in the elongated ribbon-like nanostructures (α-form). Ambipolar behavior is not observed with CuPc in the β-polymorph. Unipolar hole mobilities as high as 2.0 × 10–3 cm2 V–1 s–1 are observed in these solution-processed blend field-effect transistors (FETs) on prolonged treatment in methanol, comparable to previously reported hole mobilities in thermally evaporated CuPc FETs. These results show that ambipolar charge transport and carrier mobilities in multicomponent organic semiconductors are intricately related to the phase-separated nanoscale and crystalline morphology.

Application of regioregular polythiophene in spintronic devices: Effect of interface

Abstract: The authors report on fabrication and characterization of a polymeric spin valve with the conjugated polymer regioregular (poly 3-hexylthiophene) (RRP3HT) as the spacer layer. The device structure is La0.67Sr0.33MnO3 (LSMO)/polymer/Co, with half-metallic, spin-polarized LSMO acting as the spin-injecting electrode. The spin valve shows behavior similar to a magnetic tunnel junction though the nonmagnetic spacer layer (∼100nm) is much thicker than the tunneling limit. They attribute this behavior to the formation of a thin spin-selective tunneling interface between LSMO and RRP3HT caused by RRP3HT, chemically attaching to LSMO as observed by x-ray photoelectron spectroscopy measurement. This gives rise to ∼80% magnetoresistance (MR) at 5K and ∼1.5% MR at room temperature. They found that by introducing monolayer of different organic insulators between LSMO and RRP3HT the spin-selective interface is destroyed and the spin injection is reduced. Their results show that organic materials are promising candidate...

All-Inkjet-Printed Organic Thin-Film Transistor Inverter on Flexible Plastic Substrate

Abstract: We report an all-inkjet-printed inverter using two p-type organic thin-film transistors (OTFTs) on a flexible plastic substrate. Metal-organic precursor-type silver ink, poly-4-vinylphenol solution, and 6,13-bis (triisopropylsilylethynyl)-pentacene solution were used to print gate and source/drain electrodes, gate-dielectric layer, and active semiconductor layer, respectively. By optimizing fabrication conditions, we obtained OTFTs with a mobility of 0.02 cm2/V·s, an on/off ratio of 104, and a threshold voltage of -1.2 V, and inverters with good switching performance showing a gain of 7.8 at a supply voltage of VDD = -40 V .

Current-induced fluorescence quenching in organic light-emitting diodes

Abstract: The electroluminescence quantum efficiency of organic light-emitting diodes with a doped Alq [tris(8-quinolinolato)aluminum] emitting layer is found to decrease markedly with increasing current density. This phenomenon was investigated using multilayer device structures permitting bipolar or unipolar carrier transport, and luminescence measurements with simultaneous optical and electrical excitation. The loss of electroluminescence quantum efficiency is attributed to the quenching of the singlet-excited state of the dopant by a cationic species.

N-Heteropentacenes and N-Heteropentacenequinones:From Molecules to Semiconductors

Abstract: N-Heteropentacenes and their derivatives have been recently discoveredas a new family of organic semiconductors exhibiting high performancein organic field effect transistors (OFETs). Introducing nitrogenatoms to the pentacene moiety leads to a large number of structurallyrelated π-backbones with tunable electronic structures,stability, solubility, and molecular packing. This gives considerablefreedom when designing organic semiconductors and provides goodopportunities for studying structure-property relationships.In this account, efforts on developing N-heteropentacenes and N-heteropentacenequinonesas organic semiconductors are reviewed, with focus on the recentwork of our own group. 1 Overview 2 Brief Introduction to Organic Semiconductors and Organic FieldEffect Transistors 3 Dihydrodiazapentacenes and Diazapentacenes 4 A Dihydrotetraazapentacene and Its Methylated Derivatives 5 N-Heteropentacenequinones 6 Silylethynylated N-Heteropentacenes 7 Conclusion and Outlook