We demonstrate controllable shift of the threshold voltage and turn-on in pentacene thin film transistors rubrene single crystal field effect (FET) by use nine organosilanes with different functional groups. Prior to depositing organic semiconductors, were applied SiO2 gate insulator from solution form a self assembled monolayer (SAM). The observed transfer characteristics range -2 50 V can be related surface potential layer next transistor channel. Concomitantly mobile charge carrier...

A method has been developed to inject mobile charges at the surface of organic molecular crystals, and dc transport field-induced holes measured pentacene single crystals. To minimize damage soft fragile surface, crystals are attached a prefabricated substrate which incorporates gate dielectric (SiO2) four probe pads. The mobility ranges from 0.1 0.5 cm2/V s is nearly temperature independent above ∼150 K, while it becomes thermally activated lower temperatures when induced become localized....

We report on single crystal high mobility organic field-effect transistors prepared prefabricated substrates using a “flip-crystal” approach. This method minimizes handling and avoids direct processing of the that may degrade transistors' electrical characteristics. A chemical treatment process for substrate ensures reproducible device quality. With limited purification starting materials, hole mobilities 10.7, 1.3, 1.4cm2∕Vs have been measured rubrene, tetracene, pentacene crystals,...

We report reduced contact resistance of single-layer graphene devices by using ultraviolet ozone (UVO) treatment to modify the metal/graphene interface. The were fabricated from mechanically transferred, chemical vapor deposition (CVD) grown, single layer graphene. UVO in regions as defined photolithography and prior metal was found reduce interface contamination originating incomplete removal poly(methyl methacrylate) (PMMA) photoresist. Our control experiment shows that exposure times up...

The density of trap states in the band gap semiconducting organic single crystals has been measured quantitatively and with high energy resolution by means experimental method temperature-dependent space-charge-limited-current spectroscopy. This spectroscopy applied to study bulk rubrene crystals, which are shown this technique be chemical structural quality. A deep as low $\ensuremath{\sim}{10}^{15}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ is purest exponentially varying...

In order to gain further insight into the details of charge transport in organic semiconductor devices it is necessary characterize density trap states at semiconductor∕gate dielectric interface. Here we use technique gate bias stress quantitatively determine interface rubrene single-crystal field-effect transistors with two different types interfaces. A reversible and reproducible shift I-V characteristics observed upon both negative positive stress, whose physical origin identified as...

The operation of organic light emitting diodes (OLEDs) is governed by a range material parameters, such as frontier orbital energy levels, charge carrier mobility and excitonic rate parameters. In state-of-the art numerical simulations OLED devices, more than 30 parameters must be considered to describe the behavior multilayer device. Independent measurement techniques reliably determine each parameter individually are therefore highly desirable. While several have been established in...

We report on n-channel organic thin-film transistors (OTFTs) with field-effect mobility comparable to that typically reported for p-channel OTFTs fabricated from pentacene. The were oxidized silicon wafers using N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI–C13H27) as the semiconductor and Au, Cr, Al, LiF∕Al source drain contacts. Accumulation mode transistor operation is demonstrated all contact metals despite large differences in their work functions. High near 0.6cm2∕Vs...

We have synthesized, crystallized, and studied the structural electric transport properties of organic molecular crystals based on a rubrene derivative with $t$-butyl sidegroups at 5,11 positions. Two crystalline modifications are observed: one (A) distinct from that larger spacings between naphtacene backbones, other (B) an in-plane structure presumably very similar compared to rubrene. The reflect different structures: in latter phase (B), hole mobility...

The authors report on the modeling of water related trap state in pentacene single crystal field-effect transistors that is created by a prolonged application gate voltage [C. Goldmann et al., Appl. Phys. Lett. 88, 063501 (2006)]. find narrow energy to be appropriate explain steplike feature measured subthreshold region transfer characteristic. forms an interface layer next insulator and centered at 430±50meV above valence band edge. density increases from (2to10.5)×1018∕cm3 during bias...

It has been demonstrated [K. P. Pernstich, S. Haas, D. Oberhoff, C. Goldmann, J. Gundlach, B. Batlogg, A. N. Rashid, and G. Schitter, Appl. Phys. 96, 6431 (2004)] that a controllable shift of the threshold voltage in pentacene thin film transistors is caused by use organosilanes with different functional groups forming self-assembled monolayer (SAM) on gate oxide. The observed broadening subthreshold region indicates SAM creates additional trap states. Indeed, it well known traps strongly...

We present a modular numerical model for organic thin-film field-effect transistors (OTFTs) that allows an arbitrary density of states to be independently defined the semiconductor bulk and surface next gate insulator. can derive charge dependence on interface field as well space-charge-limited current characteristics. Together with contacts, we arrive at physical is applied series OTFTs in staggered inverted (top contact) geometry various insulator treatments

Large perturbation transient photovoltage and impedance spectroscopy measurements are used to gain insights into recombination in organic photovoltaic devices. The combination of these two simple optoelectronic techniques enables characterization order as well mobile trapped charge evolution over a large range carrier densities. data show that is approximately equal total at low densities the high efficiency devices measured. Between density, observed vary from monomolecular bimolecular...

We present an electro-optical model of a three-layer phosphorescent OLED which accurately describes the measured current efficiency and transient electroluminescence decay for different biases. Central findings are bias-dependent emission zone, influences light outcoupling as well exciton quenching, presence strong triplet-polaron quenching even at low bias. The initially increases up to 9 V before it decreases, where increase is found be caused by reduced with holes, while decrease...

Abstract Fluorescence‐based organic light‐emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) have increasingly attracted attention in research and industry. One method to implement TADF is based on an emitter layer composed of exciplex host a fluorescent dopant. Even though the experimental realization this concept has demonstrated promising external quantum efficiencies, full potential approach not yet been assessed. To end, comprehensive electro‐optical device...

We report on the origin of reduced power efficiency in a red phosphorescent OLED with an exciplex host after prolonged operation. The is solely by increased driving voltage while radiant flux remains constant. An electrical model describing increase is, thus, sufficient to explain efficiency. fresh and at different stages degradation was devised from four measurement methods. Using multiple methods determine parameters results rather unique set parameters, despite large number (38) as...

From s-polarized, angle-dependent measurements of the electroluminescence spectra in a three-layer phosphorescent organic light-emitting diode, we calculate exciton distribution inside 35 nm thick emission layer. The shape profile changes with applied bias due to differing field dependencies electron and hole mobilities. A split zone high densities at both sides layer is obtained, which explained by presence energy barriers similar peak transient signal after turn-off application reverse...

We present the observation of magnetoresistance in Co/Ca/Alq3/Ca/NiFe spin-valve devices. Thin Ca layers contacting 150 nm thick Alq3 enable injection spin-polarized electrons into due to engineering band alignment. The devices exhibit symmetric current-voltage (I–V) characteristics indicating identical metal contacts on Alq3, and up 4% positive was observed at 4.5 K. In contrast, simultaneously fabricated Co/Alq3/NiFe displayed asymmetric I–V curves different electrodes, effects were not observed.

A multi‐scale optical model for organic light‐emitting devices containing scattering layers is presented. This describes the radiation of embedded oscillating dipoles and from spherical particles. After successful validation with experiments on a top‐emitting white OLED, we show how this tool can be used optimization specific targets.

Abstract Controlled, bottom‐up self‐assembly of ordered and hierarchical structures remains a major challenge increasingly attracts attention in basic technology‐driven research. A simple process is described for the generation such structures, which based on slow solvent evaporation polymer solution blended with crystal‐forming species (Krogmann’s salt). Upon drying, viscosity polymer‐blend increases progressing solidification zone, precisely controls crystal growth by limiting transport...

We report on an empirically based physical model developed for small-molecule organic thin film transistors (OTFTs). The is extension of adapted MOSFET hydrogenated amorphous silicon TFTs accounting arbitrary energy distribution mobile and trap states allows the extraction parameters from measured device characteristics. Ideally all can be derived material properties semiconductor, but often those are masked by extrinsic effects. To provide input validation data sets we fabricated top...