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Two dyes containing of thioxanthenone derivative as an acceptor unit, were designed and synthesized for thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs). The photoluminescence (PL) spectra of hammered dyes were shifted and the dyes were mechanochromic. Ionization potential (IP) values of spin-coated dyes on the fluorine-tin oxide film ranged from-5.42 to-5.49 eV and the hole mobility values reached to 2.64 x 10(-4) and 3.56 x 10(-4) cm(2) V(- 1)s- 1.Considering the higher values of the photoluminescence quantum yields (PLQYs) of spin-coated dyes on the solid films (16, 21%) that dispersed the dyes in a solution such as toluene (7, 3%), the aggregation induced emission enhancement (AIEE) phenomena were observed. In addition, the doped devices were fabricated based on 50 wt% poly (9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) as a host material through the solution process and physically evaporation deposition (PVD). In this study, the effect of utilizing 4, 4', 4 ''& nbsp;-Tris [(3-methylphenyl) phenylamino]triphenylamine (m-MTDATA) as a hole transport layer was impressive and the exciplex forming was confirmed. Finally, the electroluminescence with CIE(x,y) of (0.2076,0.3634) was resulted for the device consisted of low turn on voltage of 4.43 V, maximum brightness of 21362.55 cd m(- 2), maximum current and power efficiency of 27.03 cd A(-1) and 19.65 lm.W-1 and maximum external quantum efficiency of 9.71%.

In this study, we designed, engineered and investigated two new thermally activated delayed fluorescence (TADF) dyes obtained from D-A-D ' type, consisted of 2-(9H-carbazol-9-yl)-3-(3-methoxy-9H-carbazol-9-yl)-9Hxanthen and 2-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3-(3-methoxy -9H-carbazol-9-yl)-9H-xanthen. In these dyes, xanthen derivative and carbazole derivatives have played important roles as an acceptor and two unsymmetrical donor units. In addition, the photophysical properties of these dyes were evaluated by the UV-VIS absorption, photoluminescence spectroscopy and photoluminescence decay lifetime analysis in solution, initial dye, nondoped and doped solid state (neat-film) at different temperatures and under the vacuum-ambient. Substitution's strong effect of the donor units was impressive; where, the dyes' ionization potential values were achieved as 5.53 and 5.62 eV. The charge mobility measurements of dyes were carried out using two different methods of space charge-limited current (SCLC) and time of the flight (TOF). Appropriate extracted results proved dyes' promising application as an emitter layer in organic light emitting diodes (OLEDs), through the photophysical properties, aggregation induced emission enhancement (AIEE) phenomenon, and high intensity of emission spectrum spanning the large part of visible area and good thermal stability. The solution process and physical evaporation deposition (PVD) procedure were tandemly performed in order to coat the layers and fabricate non-doped and doped OLEDs. The low turned on voltage' values of OLEDs were recorded in the range of 4.08 to 5.31 V. Furthermore, the maximum values of brightness, current, power and external quantum efficiency were achieved as 72565 cd/m2, 37.32 cd/A, 20.99 lm/W and 13.41%, respectively.

This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies. © 2021 The Author(s).

The search for alternative transparent electrodes to the commonly used indium tin oxide (ITO) in optoelectronic devices has led to solution-based approaches based on inkjet printing. As an additive manufacturing technique that allows drops to be positioned only where necessary, inkjet printing shows reduced waste of starting material compared to other methods such as spin coating. As a result, functional materials can be both coated and structured without the need for masks or lithographic pre-patterning of the substrate. For this contribution, we utilized a particle-free silver ink to produce a transparent electrode by inkjet printing. After printing, the silver ions were reduced to metallic silver by an argon plasma. The process takes place at low temperatures (ca. 40 – 50°C), making it suitable for use with flexible substrates, which are often temperature-sensitive. The printed silver layers show good electrical conductivity and optical transmittance, with a crystalline grain structure being formed and maintained during the metallization process. This structure forms a self-organized nanometer-size grid, whose structure allows light to pass through. Due to its nano-structured property, the haze of the electrode was investigated using a simple experimental setup based on a light source shining through the electrode and analyzing the size of the projected pattern. Such qualitative assessment can be a useful indication of the quality of the electrode and we provide details on how to replicate this setup. The final electrodes were implemented in solution-processed OLEDs, which showed bright luminance and overall low haze compared to ITO-based reference devices., Peer Reviewed

This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than that of the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 × 10−6 cm2/V) to L-H (1.9 × 10−4 cm2/V). In fact, the OLED devices based on a L-F active layer showed excellent green emission (brightness and current efficiency were 1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9% and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of the L-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.

Low‐cost flexible organic light‐emitting diodes (OLEDs) with nanoemitter material from waste open up new opportunities for sustainable technology. The common emitter materials generated from waste are carbon dots (CDs). However, these have poor luminescent properties. Further solid‐state emission quenching makes application in display devices challenging. Here, flexible and rigid OLED devices are demonstrated using self‐assembled 2D arrays of CDs derived from waste material, viz., human hair. High‐performance CDs with a quantum yield (QY) of 87%, self‐assembled into 2D arrays, are achieved by improving the crystallinity and decreasing the CDs' size distribution. The CD island array exhibits ultrahigh hole mobility (≈10−1 cm2 V−1 s−1) and significant reduction in solid‐state emission quenching compared to pristine CDs; hence, it is used here as an emitting layer in both indium tin oxide (ITO)‐coated glass and ITO‐coated flexible poly(ethylene terephthalate) (PET) substrate OLED devices, without any hole‐injection layer. The flexible OLED device exhibits a stable, voltage‐independent blue/cyan emission with a record maximum luminescence of 350 cd m−2, whereas the OLED device based on the rigid glass substrate shows a maximum luminescence of 700 cd m−2. This work sets up a platform to develop next‐generation OLED displays using CD emitters derived from the biowaste material.

Limiting by classic donor–acceptor (D–A) strategy based on charge transfer (CT) process dominated emission, the high-efficiency organic deep/near infrared red (DR/NIR) emitters with desirable photoluminescence quantum yields (PLQYs) and satisfactory excitons utilization efficiencies (EUEs) are still a challenge. Herein, three new DR/NIR luminogens (TNZPPI, TNZtPPI and TNZ2tPPI) based on naphtho[2,3-c][1,2,5]thiadiazole (NZ) group are synthesized. Their interesting characterization of hybrid excited states containing tuned local excited (LE) and CT components are confirmed, and the effective high-lying reverse intersystem crossing (RISC) channel might be activated because of their larger T2–T1 energy gap and smaller T4–S2 energy splitting. Thanks for their higher fluorescence quantum yields in film (24–38%), the TNZPs-based non-doped devices exhibit bright NIR emission with higher maximum radiance of 21447–36027 mW Sr−1 m−2, whose performance are better than most reported pure organic NIR devices. Enjoying deep analysis of their solvation effect and aggregation-induced emission (AIE)-activity, the doped organic light emitting diodes (OLEDs) are fabricated, whose performances are very good with identical National Television System Committee saturated red-emitting behaviors. The results in TNZPs show that the electronic effect of molecule structure and intermolecular interactions all are relative to their performance, and which is very important for the design high-efficiency NZ-based OLED materials. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A recent and emerging application of organic light emitting diodes (OLEDs) is in wearable technologies as they are flexible, stretchable and have uniform illumination over a large area. In such applications, transmission of OLED emission through skin is an important part and therefore, understanding spectral changes associated with transmission of OLED emission through human skin is crucial. Here, we report results on transmission of OLED emission through human skin samples for yellow and red emitting OLEDs. We found that the intensity of transmitted light varies depending on the site from where the skin samples are taken. Additionally, we show that the amount of transmitted light reduces by ~ 35–40% when edge emissions from the OLEDs are blocked by a mask exposing only the light emitting area of the OLED. Further, the emission/electroluminescence spectra of the OLEDs widen significantly upon passing through skin and the full width at half maximum increases by >20 nm and >15 nm for yellow and red OLEDs, respectively. For comparison, emission profile and intensities of transmitted light for yellow and red inorganic LEDs are also presented. Our results are highly relevant for the rapidly expanding area of non-invasive wearable technologies that use organic optoelectronic devices for sensing.

Thermal annealing of the emissive layer of an organic light emitting diode (OLED) is a common practice for solution processable emissive layers and reported annealing temperatures varies across a wide range of temperatures. We have investigated the influence of thermal annealing of the emissive layer at different temperatures on the performance of OLEDs. Solution processed polymer Super Yellow emissive layers were annealed at different temperatures and their performances were compared against OLEDs with a non-annealed emissive layer. We found a significant difference in the efficiency of OLEDs with different annealing temperatures. The external quantum efficiency (EQE) reached a maximum of 4.09% with the emissive layer annealed at 50 °C. The EQE dropped by ~35% (to 2.72%) for OLEDs with the emissive layers annealed at 200 °C. The observed performances of OLEDs were found to be closely related to thermal properties of polymer Super Yellow. The results reported here provide an important guideline for processing emissive layers and are significant for OLED and other organic electronics research communities.

type:Journal Article, Polarized polymer light-emitting diodes (PLEDs) have been constructed utilizing friction-transferred poly(9,9-dioctylfluorene) (PFO) thin films. The friction transfer technique allows oriented PFO to be deposited directly onto an indium tin oxide anode without an alignment layer such as polyimide. Polarized absorption and photoluminescence spectra revealed that the polymer backbones are highly aligned in the friction direction. We fabricated PLEDs consisting of friction-transferred PFO as an emissive layer, vacuum-deposited bathocuproine as an electron transport and hole-blocking layer, and a vacuum-deposited LiF/Al cathode. Highly polarized blue emission with an integrated polarization ratio of 31 and a luminance of up to 300 cd/m2 was observed from the PLEDs., source:https://doi.org/10.1063/1.2142082, source:http://www.aps.org

In this study, we report a contact printing technique that uses polyurethane-acrylate (PUA) polymers as the printing stamps to pattern electroluminescent layers of organic light emitting diodes (OLEDs). We demonstrate that electroluminescent thin films can be printed with high uniformity and resolution. We also show that the performance of the printed devices can be improved via postprinting thermal annealing, and that the external quantum efficiency of the printed devices is comparable with the efficiency of the vacuum-deposited OLEDs. Our results suggest that the PUA-based contact printing can be used as an alternative to the traditional shadow mask deposition, permitting manufacturing of OLED displays with the resolution up to the diffraction limit of visible-light emission.

Indium tin oxide (ITO) is the transparent electrode of choice for organic light-emitting diodes (OLEDs). Replacing ITO for cost and performance reasons is a major drive across optoelectronics. In this work, we show that changing the transparent electrode on red, blue, and yellow OLEDs from ITO to a multilayer buffered aluminium zinc oxide/silver/aluminium zinc oxide (AZO/Ag/AZO) substantially enhances total output intensity, with better control of colour, its constancy, and intensity over the full exit hemisphere. The thin Ag containing layer induces a resonant cavity optical response of the complete device. This is tuned to the emission spectra of the emissive material while minimizing internally trapped light. A complete set of spectral intensity data is presented across the full exit hemisphere for each electrode type and each OLED colour. Emission zone modelling of output spectra at a wide range of exit angles to the normal was in excellent agreement with the experimental data and hence could, in principle, be used to check and adjust production settings. These multilayer transparent electrodes show significant potential for both eliminating indium from OLEDs and spectrally shaping the emission.

Photovoltaic (PV) stand-alone systems need to achieve multiple energy conversion modes. I.e. the energy conversion from PV to a local energy storage as well as energy conversion from the energy storage to the load. This paper documents the practical design considerations for the development of a three-port-converter for this purpose optimized for the specifications for driving an Organic Light Emitting Diode (OLED) panel intended for lighting purposes. By using a three-port-converter, featuring shared components for each conversion mode, the converter reaches 97 % efficiency at 1.8 W during conversion from photovoltaic panel to the battery, and 97 % in the area 1.4 W to 2 W for power delivery to the OLED.

Liquid organic light-emitting diodes (liquid OLEDs) are unique devices consisting only of liquid organic semiconductors in the active layer, and the device performances have been investigated recently. However, the device degradation, especially, the origin has been unknown. In this study, we show that material degradation occurs in liquid OLEDs, whose active layer is composed of carbazole with an ethylene glycol chain. Nuclear magnetic resonance (NMR) experiments clearly exhibit that the dimerization reaction of carbazole moiety occurs in the liquid OLEDs during driving the devices. In contrast, cleavages of the ethylene glycol chain are not detected within experimental error. The dimerization reaction is considered to be related to the device degradation.

The diffusion of molecules through and between organic layers is a serious stability concern in organic electronic devices. In this work, the temperature-dependent diffusion of molecular dopants through small molecule hole transport layers is observed. Specifically we investigate bilayer stacks of small molecules used for hole transport (MeO-TPD) and p-type dopants (F4TCNQ and C60F36) used in hole injection layers for organic light emitting diodes and hole collection electrodes for organic photovoltaics. With the use of absorbance spectroscopy, photoluminescence spectroscopy, neutron reflectometry, and near-edge X-ray absorption fine structure spectroscopy, we are able to obtain a comprehensive picture of the diffusion of fluorinated small molecules through MeO-TPD layers. F4TCNQ spontaneously diffuses into the MeO-TPD material even at room temperature, while C60F36, a much bulkier molecule, is shown to have a substantially higher morphological stability. This study highlights that the differences in size/geometry and thermal properties of small molecular dopants can have a significant impact on their diffusion in organic device architectures.

The aim of this study is to know the limits, advantages and disadvantages of the organic light emitting diodes (OLED) to be used as a lighting source in the gear shifter manufacturing. To do this we developed a prototype that was illuminated with a flexible deep blue OLED and analysed their emission in terms of luminance and colour across its surface as well as over time. We also conducted a durability test at room temperature with periodical photometric and colorimetric measurements. The results were analysed taking into account the recommendations of the engineering specification based on a German standard used for this purpose.

Bottom emitting organic light emitting diodes (OLEDs) can suffer from lower external quantum efficiencies (EQE) due to inefficient out-coupling of the generated light. Herein, it is demonstrated that the current efficiency and EQE of red, yellow, and blue fluorescent single layer polymer OLEDs is significantly enhanced when a MoOx(5 nm)/Ag(10 nm)/MoOx(40 nm) stack is used as the transparent anode in a top emitting OLED structure. A maximum current efficiency and EQE of 21.2 cd/A and 6.7%, respectively, was achieved for a yellow OLED, while a blue OLED achieved a maximum of 16.5 cd/A and 10.1%, respectively. The increase in light out-coupling from the top-emitting OLEDs led to increase in efficiency by a factor of up to 2.2 relative to the optimised bottom emitting devices, which is the best out-coupling reported using solution processed polymers in a simple architecture and a significant step forward for their use in large area lighting and displays.

Since Tang and VanSlyke developed the first organic light emitting diode (OLED) in the late 80’s using tris-(8-hydroxyquinoline) aluminium (Alq3) as both the emissive and electron transporting layer, a lot of research has been done on Alq3 and other metal quinolates (Mqx). The optical, morphological and electrical properties of these Mqx have been studied extensively. Alq3 has, however, a disadvantage as it tends to degrade when stored under atmospheric conditions. These degraded products are non-luminescent and lead to poor device performance. A good understanding of what happens during the degradation process and ways of eliminating this process are needed. In this study different Mqx compounds were synthesized and their degradation behavior was studied to see what effect it has on their luminescent properties. One way to tune the emissive colour of Alq3 is to introduce electron-withdrawing or electron-donating groups (EWG and EDG) onto the hydroxyquinoline ligands. These groups have an effect on the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. In this study Alq3 powders were synthesized with an EDG (-CH3) substituted at position 5 and 7 ((5,7-dimethyl-8-hydroxyquinoline) aluminium) (5,7Me-Alq3) and EWG (-Cl) at position 5 ((5-chloro-8-hydroxyquinoline) aluminium) (5Cl-Alq3). A broad absorption band at ~ 380 nm was observed for un-substituted Alq3. The bands of the substituted samples were red shifted. The un-substituted Alq3 showed a high intensity emission peak at 500 nm. The 5Cl-Alq3 and 5,7Me-Alq3 samples showed a red shift of 33 and 56 nm respectively. Optical absorption and cyclic voltammetry measurements were done on the samples. The optical band gap was determined from these measurements. The band gap did not vary with more than 0.2 eV from the theoretical value of Alq3. The photon degradation of the samples was also investigated and the 5,7Me-Alq3 sample showed the least degradation to the UV irrad, National Research Foundation (NRF), University of the Free State

The focus of the Center is to develop and demonstrate novel materials, both for device structures that advance the state-of-the-art in flexible electronics, as well as for environmentally-stable, hybrid, organic/inorganic semiconductors, leading to robust luminescent devices for flexible displays for the U.S. soldier. Performance of transparent and conducting oxides of indium tin oxide and F-doped ZnO films on plastics and their stability under mechanical deformation were investigated. Thin film transistors (TFTs) with gallium tin zinc oxide (GSZO) channels, using the bottom gate configuration, were fabricated on thermally grown silicon dioxide on Si wafers. The best TFT electrical characteristics, with a threshold voltage of 4V and a drain current of 10-6A with an on/off current ratio as high as 10(exp 6), have been obtained on RT deposited channel layers, annealed subsequently in air at 250 deg C for 1 hr. on a 50 micron channel length and width. Inverted, hybrid organic light emitting diode structures that integrates inorganic and organic semiconductors layers were developed, with threshold voltage 6V, efficiency 2cd/A with operating lifetimes 500 hours without encapsulation. Preliminary results on monolayer molecular functionalization of inorganic semiconductors and charge injection from inorganic to organic semiconductors have been shown., Prepared in cooperation with RTI International, Research Triangle Park, NC.

Non see-through, monocular helmet mounted displays (HMDs) provide warfighters with unprecedented amounts of information at a glance. The US Air Force recognizes their usefulness, and has included such an HMD as part of a kit for ground-based, Battlefield Airmen. Despite their many advantages, non-see-through HMDs occlude a large portion of the visual field when worn as designed, directly in front of the eye. To address this limitation, operators have chosen to wear it just above the cheek, angled up toward the eye. However, wearing the HMD in this position exposes the display to glare, causing a potential viewing problem. In order to address this problem, we tested several film and HMD hood applications for their effect on glare. The first experiment objectively examined the amount of light reflected off the display with each application in a controlled environment. The second experiment used human participants to subjectively evaluate display readability/legibility with each film and HMD hood covering under normal office lighting and under a simulated sunlight condition., Prepared in collaboration with Oak Ridge Associated Universities, Belcamp, MD.

DNA, the beautifully symmetrical molecule of life, carries the core genetic blueprint for every living organism. Now, through the emerging field of DNA photonics, it also has the potential to serve as an inexpensive, renewable resource in the development of optical waveguides, organic LEDs and laser structures., Prepared in collaboration with Air Force Research Laboratory, Wright-Patterson AFB, OH. Published in OPN Optics & Photonics News, p35-39, July-August 2011.

Organic light emitting diodes (OLEDs) prepared from electroactive materials show great potential for multicolor display and white light source applications. Unfortunately, the commercialization of multilayer OLEDs has been slow. This can be attributed in part to the vapor deposition technique used to assemble small molecule thin films. The process is not amenable to large area displays and is relatively costly. An attractive alternative solution to this problem is to replace small molecules with organic polymers, which could be solution processed in an efficient and economical manner. Polymeric materials also offer the unique potential to achieve nanoscale self-assembled structures through their functional architecture. These materials can be solution processed and mimic multilayered small molecule devices to achieve improved performance and/or balanced color. Design and synthesis and OLED testing of functional polymers which can achieve defined multilayer or nanostructured film characteristics through simple solution processing is the focus of this thesis. In Chapter 1, the history of OLED materials as well as the device mechanism and key organic electronic characteristics necessary for high performance devices is introduced. There is also a discussion on the methods for device testing and characterization. The design and synthesis of novel dendronized linear polymer host materials is presented in Chapter 2. These polymers should possess a rigid linear rod like architecture which had not been investigated for its potential to order a thin film in an assembly of cylindrical structures. This host material was desired in order to optimize the interface of hole and electron transporting material to achieve improved recombination in the thin film. Similarly, in Chapter 3 a diblock copolymer architecture is studied as host material in OLED devices. In this work the differences between nanoscale self assembled diblock copolymers of hole and electron transporting units and

We have shown that triazine compounds of 2-biphenyl-4-yl-4,6-bis-(4′-pyridin-2-yl-biphenyl-4-yl)-[1,3,5]triazine (DPT) and 2,4-bis-biphenyl-4-yl-6-(4′-pyridin-2-yl-biphenyl-4-yl)-[1,3,5]triazine (MPT) work as excellent electron-transport layers (ETLs) of organic light-emitting diodes (OLEDs). By replacing a typical ELT of tris(8-hydroxyquinoline) aluminum (Alq_3) with the DPT ETL and the MPT ETL, driving voltages and power conversion efficiencies of OLEDs operated at a current density of 50 mA cm^<−2> are improved from 7.7 ± 0.2 V and 1.41 ± 0.10 lm W^<−1> (Alq_3) to 6.0 ± 0.1 V and 1.62 ± 0.09 lm W^<−1> (DPT) and 5.2 ± 0.1 V and 1.88 ± 0.18 lm W^<−1> (MPT), respectively. Half lifetimes of the OLEDs operated at the same current are also enhanced from 3200 h (Alq_3) to 4200 h (MPT) by using the MPT ETL. The reduction in driving voltage is found to arise from more efficient electron injection at interfaces of DPT/cathode (a barrier height of ≈0.61 eV) and MPT/cathode (a barrier height of ≈0.51 eV) than at an interface of Alq_3/cathode (a barrier height of ≈0.73 eV) as well as better electron mobilities of DPT (8.7 × 10^<−5> cm^2 V^<−1> s^<−1> at an electric field of 5.0 × 10^5 V cm^<−1>) and MPT (1.4 × 10^<−4> cm^2 V^<−1> s^<−1> at the same field) than that of Alq3 (4.1 × 10^<−6> cm^2 V^<−1> s^<−1> at the same field [Naka et al., Synth. Met. 111–112 (2000) 331.]). A high-mobility electron-transport material of 4,7-diphenyl-1,10-phenanthroline (Bphen) is also used as an ETL for comparison of OLED characteristics.

Tithe-dependent density functional theory with quadratic response methodology is used in order to calculate and compare spin-orbit coupling effects and the main mechanism of phosphorescence of the neutral Ir(ppy)(3) and cationic [Ir(bpy)(3)](3+) tris-iridium compounds, [Ir(ppy)(2)(bpy)](+) and [Ir(2-phenylpyridine)(2)(4,4'-tert-butyl-2,2'-bipyridine](+) complexes, including also the recently synthesised [Ir(2-phenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) and [Ir(2,4-difluorophenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) dyes, where ppy = 2-phenylpyridine and bpy = 2,2'-bipyridine ligands. Comparison with the symmetric, lighter and more studied [Ru(bpy)(3)](2+) and [Rh(bpy)(3)](3+) complexes is also resented. Variations in lifetimes for Ir(ppy)(3) and [Ir(bpy)(3)](3+) dyes as well as for the mixed cationic complexes are well reproduced by the quadratic response method. All the ortho-metalated iridium compounds exhibit strong phosphorescence, which is used in organic light-emitting diodes (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. The results from the first principle theoretical analysis of phosphorescence have helped to clarify the connections between the main features of electronic structure and the photo-physical properties of the studied heavy organometallic OLED materials., QC 20110415

Thin film transistors based on polyarylamine poly(N,N'-diphenyl-N,N'bis(4-hexylphenyl)-[1,1'biphenyl]-4,4'-diamine (pTPD) were fabricated using spin coating in order to measure the mobility of pTPD upon oxidation. Partially oxidized pTPD with a molecular magnetic cluster showed an increase in mobility of over two orders of magnitude. A transition in the mobility of pTPD upon doping could also be observed by the presence of a maximum obtained for a given oxidant ratio and subsequent decrease for a higher ratio. Such result agrees well with a previously reported model based on the combined effect of dipolar broadening of the density of states and transport manifold filling., Peer Reviewed, Postprint (published version)

The overall work focused on Nanophase Enhanced Optical Devices. Two projects Transparent Ceramics for Infrared Window and Laser Applications, and Broadband-Absorbing Polymer-Metal Nanocomposites for Photovoltaic Applications comprised this effort. The objectives for the first project were (i) to fabricate transparent yttria ceramics from commercially available nanopowder with a grain size significantly smaller than 100 micrometer and a transmittance in the infrared close to the theoretical maximum; and (ii) to fabricate polycrystalline Er,Yb:Y(2)O(3) ceramics, suitable as solid-state laser materials in the eye- safe wavelength range. The objective for the second project was to fabricate an organic photovoltaic device that absorbs solar radiation between 400 nm and 2500 nm and has a power conversion efficiency of 5% or better. A research laboratory was set up to synthesize, process, and characterize ceramic materials and polymer-metal nanocomposites. A transparent yttria ceramic with an average grain size of about 20 micrometer and good optical transparency was prepared and characterized. Yttria nanoparticles codoped with erbium and ytterbium were successfully prepared and characterized. Polymer-metal nanocomposites were successfully prepared and it was demonstrated that their absorption spectrum can be tailored to match the solar radiation.

This report was prepared as a trade study review of current and projected active camouflage systems. While numerous applications were discussed, the focus was for systems that could be used by infantry soldiers, and specifically for infantry helmet applications. A review of the current and projected active camouflage systems revealed that there are many systems under development for aviation, maritime, and ground operations. Early prototypes for infantry soldiers were presented in detail. A system overview was prepared in order to present camera, image processing, and display solutions. Finally, a discussion focusing on technology limitations, applications, and future considerations was presented. This trade study showed that numerous technologies for active camouflage systems are under development; however major technical roadblocks must be addressed before systems will be ready for infantry applications., The original document contains color images. Abstract in English and French.

Nonemissive tetraphenylethene (TPE) 1 and its diphenylated derivative 2 were induced to emit intensely by aggregate formation. Crystalline aggregates of the dyes emitted bluer lights than their amorphous counterparts. The emissions of the TPE dyes could be switched off and on continuously and reversibly by wetting and dewetting with solvent vapors, respectively, manifesting their ability to optically sense volatile organic compounds. The light-emitting diodes fabricated from 1 and 2 were turned on at similar to 2.9 and similar to 5 V and emitted blue lights with maximum luminance of similar to 1800 and similar to 11 000 cd/m(2), respectively. (c) 2007 American Institute of Physics.

Práce se zabývá studiem zářivé rekombinace excitovaných stavů v organických materiálech vyvolaných optickou a elektrickou excitací. Tyto procesy jsou studovány pomocí optických spektroskopických metod a charakterizací elektroluminiscence. V teoretické části je provedena rešerše a jsou shrnuty základní poznatky nutné pro interpretaci dat se zaměřením na fluorescenci organických látek. Dále jsou diskutovány procesy přeměny elektrické energie na elektromagnetické záření v organických elektroluminiscenčních diodách. Praktická část zahrnuje přípravu modelových diod, studium jejich optických vlastností a charakterizaci jejich elektroluminiscence., The thesis deals with study of the radiation recombination of excited states in organic materials, induced by optical and electrical excitation. These processes are studied by optical spectroscopic methods and characterization of electroluminiscence. The theoretical part contains search and summary of basic knowledge necessary for interpretation of data focusing on the fluorescence of organic substances. The conversion processes of electric energy to an electromagnetic radiation in organic electroluminiscence diods were also discussed in the thesis. The practical part describes preparation of model diods, the study of their optical properties and characterization of their electroluminescence.

Práce se zabývá studiem zářivé rekombinace excitovaných stavů v organických materiálech vyvolaných optickou a elektrickou excitací. Tyto procesy jsou studovány pomocí optických spektroskopických metod a charakterizací elektroluminiscence. V teoretické části je provedena rešerše a jsou shrnuty základní poznatky nutné pro interpretaci dat se zaměřením na fluorescenci organických látek. Dále jsou diskutovány procesy přeměny elektrické energie na elektromagnetické záření v organických elektroluminiscenčních diodách. Praktická část zahrnuje přípravu modelových diod, studium jejich optických vlastností a charakterizaci jejich elektroluminiscence., The thesis deals with study of the radiation recombination of excited states in organic materials, induced by optical and electrical excitation. These processes are studied by optical spectroscopic methods and characterization of electroluminiscence. The theoretical part contains search and summary of basic knowledge necessary for interpretation of data focusing on the fluorescence of organic substances. The conversion processes of electric energy to an electromagnetic radiation in organic electroluminiscence diods were also discussed in the thesis. The practical part describes preparation of model diods, the study of their optical properties and characterization of their electroluminescence.

Práce se zabývá studiem zářivé rekombinace excitovaných stavů v organických materiálech vyvolaných optickou a elektrickou excitací. Tyto procesy jsou studovány pomocí optických spektroskopických metod a charakterizací elektroluminiscence. V teoretické části je provedena rešerše a jsou shrnuty základní poznatky nutné pro interpretaci dat se zaměřením na fluorescenci organických látek. Dále jsou diskutovány procesy přeměny elektrické energie na elektromagnetické záření v organických elektroluminiscenčních diodách. Praktická část zahrnuje přípravu modelových diod, studium jejich optických vlastností a charakterizaci jejich elektroluminiscence., The thesis deals with study of the radiation recombination of excited states in organic materials, induced by optical and electrical excitation. These processes are studied by optical spectroscopic methods and characterization of electroluminiscence. The theoretical part contains search and summary of basic knowledge necessary for interpretation of data focusing on the fluorescence of organic substances. The conversion processes of electric energy to an electromagnetic radiation in organic electroluminiscence diods were also discussed in the thesis. The practical part describes preparation of model diods, the study of their optical properties and characterization of their electroluminescence.

Práce se zabývá studiem zářivé rekombinace excitovaných stavů v organických materiálech vyvolaných optickou a elektrickou excitací. Tyto procesy jsou studovány pomocí optických spektroskopických metod a charakterizací elektroluminiscence. V teoretické části je provedena rešerše a jsou shrnuty základní poznatky nutné pro interpretaci dat se zaměřením na fluorescenci organických látek. Dále jsou diskutovány procesy přeměny elektrické energie na elektromagnetické záření v organických elektroluminiscenčních diodách. Praktická část zahrnuje přípravu modelových diod, studium jejich optických vlastností a charakterizaci jejich elektroluminiscence., The thesis deals with study of the radiation recombination of excited states in organic materials, induced by optical and electrical excitation. These processes are studied by optical spectroscopic methods and characterization of electroluminiscence. The theoretical part contains search and summary of basic knowledge necessary for interpretation of data focusing on the fluorescence of organic substances. The conversion processes of electric energy to an electromagnetic radiation in organic electroluminiscence diods were also discussed in the thesis. The practical part describes preparation of model diods, the study of their optical properties and characterization of their electroluminescence.