Organic semiconductor

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

Thin-film transistors based on well-ordered thermally evaporated naphthacene films

Abstract: We report on organic thin-film transistors fabricated using the small-molecule organic semiconductor naphthacene as the active layer material with device performance suitable for several large-area or low-cost electronics applications. We investigated naphthacene thin films deposited by thermal evaporation onto amorphous substrates held near room temperature. Using atomic-force microscopy and x-ray diffraction we find naphthacene films consist of a high density of submicron-sized grains with a surprisingly high degree of molecular order. Thin-film transistors fabricated using evaporated naphthacene films on thermally oxidized silicon substrates have field-effect mobility larger than 0.1 cm2/V s, current on/off ratio greater than 106, negative threshold voltage, and subthreshold slope of 1 V/decade.

Electron mobility in tris(8-hydroxy-quinoline)aluminum thin films determined via transient electroluminescence from single- and multilayer organic light-emitting diodes

Abstract: Transient electroluminescence (EL) from single- and multilayer organic light-emitting diodes (OLEDs) was investigated by driving the devices with short, rectangular voltage pulses. The single-layer devices consist of indium-tin oxide (ITO)/tris(8-hydroxy-quinoline)aluminum (Alq3)/magnesium (Mg):silver (Ag), whereas the structure of the multilayer OLEDs are ITO/copper phthalocyanine (CuPc)/N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB)/Alq3/Mg:Ag. Apparent model-dependent values of the electron mobility (μe) in Alq3 have been calculated from the onset of EL for both device structures upon invoking different internal electric field distributions. For the single-layer OLEDs, transient experiments with different dc bias voltages indicated that the EL delay time is determined by the accumulation of charge carriers inside the device rather than by transport of the latter. This interpretation is supported by the observation of delayed EL after the voltage pulse is turned off. In the multilayer OLED the ...

Surface analytical studies of interfaces in organic semiconductor devices

Abstract: Surface and interface analytical studies have generated critical insight of the fundamental processes at interfaces involving organic semiconductors. I will review surface analytical studies of interface formation of organic semiconductors with different materials. Metal/organic interface is a focus of both device engineering and basic science, since it is a key factor in nearly all important aspects of device performances, including operation voltages, degradation, and efficiency. I will discuss metal–organic interface dipole formation, charge transfer, chemical reaction, energy level alignment, in-diffusion, quenching of luminescence and possible recovery of it. The effect of the insertion of ultra-thin interlayers such as LiF and doping by alkali metals will also be discussed. In organic/organic interface, the energy offset between the two dissimilar organic materials is vitally important to efficient device operation of organic light emitting diodes (OLED), as well as change separation at donor–acceptor interface in organic photovoltaic devices (OPV). I will discuss the interface energy level alignment, band bending, Debye screening, and charge separation dynamics as observed in surface analytical studies, and the implications to OLED and OPV. The interfaces of OSCs with other inorganic materials are also important. For organic thin film transistors (OTFT), the electronic properties of the interface formed between the organic and the dielectric strongly influences the current–voltage characteristics, as the electronic activity has been shown to occur primarily at the interface between the dielectric and the organic materials. I will review the interface formation of OSCs with dielectric materials and with indium-tin-oxide (ITO), a material whose transparency and conductivity make it indispensable for a number of opto-electronic applications and whose electronic properties and energy level alignment with organics have proven dramatically altered by surface treatments.

Air Stable n-Channel Organic Semiconductors for Thin Film Transistors Based on Fluorinated Derivatives of Perylene Diimides

Abstract: A series of n-type organic semiconductors based on perylene diimides were synthesized. These materials were fully characterized by FTIR and UV−vis spectra as well as elemental analysis. Thin film transistors (TFTs) using a top-contact geometry were fabricated by vapor deposition of these perylene diimide derivatives as the semiconductive channel on surface treated SiO2/Si substrates at various substrate temperatures. The measured TFT performance depended heavily on the type and the number of substituents. We found higher field-effect mobilities for compounds with stronger electron-withdrawing substituents. TFTs with fluorinated perylene diimides showed much better performance in air than a chlorinated derivative. The highest mobility, ca. 0.068 cm2/V s, was measured for the compound with the most fluorine substituents (i.e., N,N‘-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide (8)). The effect of molecular structure on film morphology was observed using an atomic force microscope (AFM). The cor...

Systems Chemistry Approach in Organic Photovoltaics

Abstract: The common approach in organic materials science is dominated by the perception that the properties of the bulk materials are virtually determined by the properties of the molecular building blocks. In this Concept Article, we advocate for taking into account supramolecular organization principles for all kinds of organic solid-state materials, irrespective of them being crystalline, liquid crystalline, or amorphous, and discuss a showcase example, that is, the utilization of merocyanine dyes as p-type organic semiconductors in bulk heterojunction (BHJ) solar cells. Despite their extraordinarily large dipole moments, which are considered to be detrimental for efficient charge carrier transport, BHJ organic photovoltaic materials of these dyes with fullerenes have reached remarkable power conversion efficiencies of meanwhile nearly 5 %. These at the first glance contradictory properties are, however, well-understandable on the systems chemistry level.