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Before the thought process of Organic Light Emitting Diodes (OLED), the then-existing technology for display and lighting applications were cathode ray tubes, tungsten bulbs, plasma display panels (PDP), and liquid crystal displays (LCD). Later, a new field concerned with energy-efficient organic electronic materials emerged for display purposes. Since the 1960s, thousands of new compounds/molecules with different structures and architectures have been reported that can be used as emissive material in OLEDs. Polymers, oligomers, polymer-metal complexes, and even small molecules can be used as emissive layers in OLEDs. Interestingly, compounds derived from organic heterocycles are appealing candidates for generating intriguing materials, such as low-bandgap semiconductors, high-potential semiconductors, photovoltaic materials, luminescent materials, and high-performance polymer solar cells. Among the heterocyclic organic compounds, thiophene is considered an efficient precursor to produce such highly applicable small molecules. This review focuses on thiophene-based small molecules, in which electrochemical, optical, and electrical properties of Organic Light-Emitting Diodes (OLED) are controlled by electron donor and electron acceptor moieties. [ABSTRACT FROM AUTHOR]

Before the thought process of Organic Light Emitting Diodes (OLED), the then-existing technology for display and lighting applications were cathode ray tubes, tungsten bulbs, plasma display panels (PDP), and liquid crystal displays (LCD). Later, a new field concerned with energy-efficient organic electronic materials emerged for display purposes. Since the 1960s, thousands of new compounds/molecules with different structures and architectures have been reported that can be used as emissive material in OLEDs. Polymers, oligomers, polymer-metal complexes, and even small molecules can be used as emissive layers in OLEDs. Interestingly, compounds derived from organic heterocycles are appealing candidates for generating intriguing materials, such as low-bandgap semiconductors, high-potential semiconductors, photovoltaic materials, luminescent materials, and high-performance polymer solar cells. Among the heterocyclic organic compounds, thiophene is considered an efficient precursor to produce such highly applicable small molecules. This review focuses on thiophene-based small molecules, in which electrochemical, optical, and electrical properties of Organic Light-Emitting Diodes (OLED) are controlled by electron donor and electron acceptor moieties. [ABSTRACT FROM AUTHOR]

OLED technology utilizes the light-emitting properties of organic materials to achieve independent color control over each pixel and even enable turning off specific pixels. These features enable OLED screens to display dark color more accurately than LCD. This paper explores the advancements in OLED technology regarding hardware structures, color control, and dimming methods. Pulse width modulation (PWM) dimming involves rapidly cycling the emission of light on and off, and provides efficient brightness control. However, some individuals may be more sensitive to potential visual fatigue or flickering. PWM dimming in OLED displays also poses potential risks to vision impairment, as it differs from traditional methods in controlling brightness. To address the drawbacks of PWM dimming, smartphone manufacturers have developed a method called "DC-like dimming." This method adjusts pixel levels closer to black or white without altering the actual screen brightness, thus reducing visual fatigue and potential eye harm. Future improvements may involve setting a lower minimum emission voltage with an additive approach to adjust brightness. [ABSTRACT FROM AUTHOR]

One of the important and difficult issues in indoor location detection utilizing global navigation systems is position estimate and approximation. This work is concerned with the indoor human tracking system based on the power contained in a received radio signal which is known as received signal strength indicator (RSSI). The real practical model handles a maze consists of seven rooms with different dimensions in single floor. Node MCU ESP8266 Microcontroller, serial communication, lithium-ion battery, OLED display, micro USB charger, and HC-05 Bluetooth model are among the hardware components utilized, which are compact in size, low in power, cheap in cost, and provide a high-speed response. Wi-Fi is used to collect software data, which is then communicated over Bluetooth. The system works with the information offline to acquire site information and then online to identify the location during system operation. The speed of the proposed indoor positioning system is fast with high accuracy. [ABSTRACT FROM AUTHOR]

We demonstrate alternating-current (AC)-driven colour-tunable organic light-emitting diodes (OLEDs) with vertically stacked green and red phosphorescent OLED units. Optically optimized thicknesses of hole and electron transporting layers were investigated through optical simulation. In addition, two types of red host materials were used for the red OLED unit, and the red OLED unit with 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl showed higher current efficiency compared to that of the red OLED unit with 2,6-Bis(3-(9H-carbazol-9-yl)phenyl)pyridine. The fabricated colour-tunable exhibited red and green colours when the duty ratio was 1% and 99%, respectively. Furthermore, the device can produce various colours that are a mixture of green and red by adjusting the AC-driving duty ratios. [ABSTRACT FROM AUTHOR]

Charge carrier recombination is a fundamental process in the operation of light emitting diodes (LEDs). Radiative carrier recombination produces light, which is the desired output for LEDs, and hence should be maximized, whereas the other carrier recombination processes should be minimized. A new model for quantifying the net carrier recombination rate in semiconductor devices (including LEDs) has been proposed recently, asserting that the new model gives a more realistic description of the carrier recombination processes in semiconductor devices than the conventional carrier recombination model. In this paper, we compare between the use of the new and the conventional carrier recombination models in modeling organic LEDs (OLEDs), particularly in predicting and analyzing the current-voltage (J-V) characteristics of OLEDs. It is shown that the J-V characteristics of OLEDs obtained using the new recombination model differ significantly compared with the J-V characteristics obtained using the conventional recombination model. Therefore, further studies are urgently needed to decisively determine which one of the two models is the more accurate model for describing the net carrier recombination rate in OLEDs (or in semiconductor devices in general) so that the more accurate model can be used when analyzing and predicting the performance of OLEDs. [ABSTRACT FROM AUTHOR]

Charge carrier recombination is a fundamental process in the operation of light emitting diodes (LEDs). Radiative carrier recombination produces light, which is the desired output for LEDs, and hence should be maximized, whereas the other carrier recombination processes should be minimized. A new model for quantifying the net carrier recombination rate in semiconductor devices (including LEDs) has been proposed recently, asserting that the new model gives a more realistic description of the carrier recombination processes in semiconductor devices than the conventional carrier recombination model. In this paper, we compare between the use of the new and the conventional carrier recombination models in modeling organic LEDs (OLEDs), particularly in predicting and analyzing the current-voltage (J-V) characteristics of OLEDs. It is shown that the J-V characteristics of OLEDs obtained using the new recombination model differ significantly compared with the J-V characteristics obtained using the conventional recombination model. Therefore, further studies are urgently needed to decisively determine which one of the two models is the more accurate model for describing the net carrier recombination rate in OLEDs (or in semiconductor devices in general) so that the more accurate model can be used when analyzing and predicting the performance of OLEDs. [ABSTRACT FROM AUTHOR]

This paper proposes a unique technique for increasing the intensity and external quantum efficiency (EQE) of white organic light emitting diodes (OLEDs) by incorporating micro/nano-metric structures such as plano-convex and plano-concave nano-lens array, and micro-pillars array on the substrate layer. The simulations were carried out using finite difference time domain method. The basic OLED model produced an EQE of 14.93% where the effective refractive index (ERI) was 1.83. On the contrary, the plano-convex elliptical nano-lens array engraved OLED showed an EQE of 16.32% for ERI of 1.75, which was highest among all kinds of OLEDS. Moreover, plano-convex elliptical nano-lens array engraved OLED exhibited significant improvement of electroluminescence light intensity that was∼15 times higher than the basic OLED at the Near Field. The wavelength spectrum confirmed the generation of white light. Because of the excellent light intensity, efficiency, and light distribution, plano-convex elliptical nano-lens array based OLED can be regarded as a potential candidate of white OLED. [ABSTRACT FROM AUTHOR]

The paper presents design and experimental investigation of an electronic system for control of the temperature of exhaust gases and the turbocharging air pressure in turbochargers of diesel automobile engines. The existing problems are faults in the fuel system of an engine. The indicators are changes in the values of the temperature and pressure in exact areas of the turbocharger. The presented device is a controller that monitors precisely the temperature and pressure, which are so vital for the long operation of the automobile. The control system is based on Arduino microcontroller. OLED Display has been added to visualize the obtained results. A schematic diagram of an electronic module for control of the temperature of exhaust gases and turbocharging air pressure in turbochargers of diesel automobile engines has been synthesized. The system has been investigated in laboratory conditions and practically implemented in a real automobile. As a result of laboratory experimental investigation, results were obtained for the time-monitored parameters temperature of the exhaust gases and turbocharging air pressure in the turbocharger system of a diesel automobile engine. [ABSTRACT FROM AUTHOR]

A comprehensive simulation model is presented for the quantitative analysis of the carrier transport and optical properties of a trilayer OLED device (ITO/NPB/Alq3/TPBi/Al) structure. It is evident from the J-V curve and depicted when a turn-on (knee) voltage is 6 V, the mean current density and electrical input power is 10 µA/cm2 and 59 µW/cm2, respectively. The device performance factor-like external quantum efficiency (EQE) is 55-66% in the wavelength region 300 to 450 nm, 4.35 for Vbias=8 V, and 6% at 50 nm thick EML. Among the different thicknesses, a quite remarkable improvement for the 50 nm thick EML has luminance concerning charge density 10,000 cd/m2 and the bias voltage by about 700 cd/m2. The spectral irradiance for the OLED device is 0.06 Wm−2nm−1sr−1 maximum in the spectral region 400-760 nm. Thus, the CIE curve studied at a distinct angle and peak get shifted at different EML thickness that show the case of thickness dependence. This study also provides an effective way to further optimize the efficiency of the OLED device with a better suitable thickness. [ABSTRACT FROM AUTHOR]

Polyaniline-Yttrium Oxide (PANI-Y2O3) nanocomposites were synthesized via chemically oxidative polymerization process. The formation of PANI, and PANI-Y2O3 nanocomposites with their corresponding changes in nanostructured properties were examined by Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction Spectroscopy (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The UV-Vis analysis exhibited PANI-Y2O3 nanocomposite possess lower band gap and higher absorption intensity than pristine PANI. The PL spectra of PANI and PANI-Y2O3 nanocomposite reveals four bands as violet, blue, green and orange bands due to non-radiative recombination of electron-hole pair. The electrical properties for PANI-Y2O3 nanocomposite showed 78 % enhancement in current density. The PANI-Y2O3 nanocomposite exhibited enhanced carrier density and excellent rate of electron-hole recombination that proposed to be suitable candidate for electron transport layer in OLED devices. [ABSTRACT FROM AUTHOR]

The development of 5G (fifth generation) mobile communication systems was initiated to meet the expected need for higher data rates. In this article, a new 28/38 GHz dual-band "inverted-F" array antenna for 5G applications is proposed. This antenna can be integrated in OLEDs (Organic Light Emitting Diodes) panels which can be used both for lighting or display. This 5G antenna, composed of 32 elements, has the advantage of a dual-band and compact structure. Each element of the array antenna has the shape of an "inverted-F" antenna. This array antenna can cover the 28 GHz band (27.94-28.83 GHz) and the 38 GHz band (37.97-38.96 GHz) with mutual coupling between the elements less than -35 dB. The characteristics of the end fire radiation beams were obtained by employing an array of 32 "inverted-F" antenna elements on the upper and lower portions of the PCB (Printed Circuit Board). The suggested design has a gain of approximately 16.52 dB at 28.38 GHz and 15.35 dB at 38.49 GHz, which is suitable for 5G mobile communications. [ABSTRACT FROM AUTHOR]

Organic semiconductor have been discovered in different application devices such as organic light emitting diodes (OLEDs). Poly [2-methoxy-5(2’ –ethylhexyloxy)-1, 4- phenylenevinylene), MEH-PPV used in optoelectronic devices because it is easily synthesizing and deposit in high molecular weight and good purity. The evaporating temperature at 750°C with 5 sccm flow of ZnO, the weight of 5 mg/ml and temperature at 50°C were chosen to fabricate MEH-PPV: ZnO nanocomposites on the optimal properties. MEH-PPV: ZnO nanocomposites was prepared by spin coating technique at room temperature. MEH-PPV: ZnO nanocomposites thin film was investigated at pure MEH-PPV (0 wt%) and 0.2 wt% of ZnO. The surface morphology revealed that 0.2 wt% of ZnO showed uniformity and less aggregation compared to MEH-PPV thin film. The electrical properties showed that the ZnO composition at 0.2 wt% exhibits the highest conductivity of 7.40 x 10-1 S. cm-1 compared to polymer thin film this value suitable applied in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The PPY, PANI and PPY-PANI-ZnO nanocomposite were prepared via chemical oxidative polymerization method using ammonium persulfate as oxidant in the laboratory. The successful embodiment of ZnO in the surface of PPY-PANI was confirmed by Fourier transform inferred spectroscopy (FTIR) analysis. The nano-flakes of ZnO were completely covered by PPY-PANI fibrous spherical ball like structure as studied by the surface morphological images. An enhanced current density ~ 164.81 % and high non-radiative recombination of electron-hole was observed with significantly enhanced conductivity for 15 % PPY-PANI-ZnO nanocomposite. The high dielectric constant (~ 895) at 333 K with high electrochemical reduction potential (~ +0.650 V) and high electron-hole recombination rate specified that it can used as electron transporting layer material for OLED devices. [ABSTRACT FROM AUTHOR]

We fabricated the electron-only devices (EODs) based on tris-(8-hydroxyquinoline) aluminum (Alq3) as an electron transport layer (ETL) with the structure of ITO/Alq3 as ETL/LiF/Al and the devices were exposed under the normal ambient for various time periods of aging. The EODs after 6 hrs of aging showed the higher electron current density (1.516 mA/cm² at 4 V, 3.472 mA/cm² at 6V, and 6.443 mA/cm² at 8V) when compared to that (0.406 mA/cm² at 4V, 0.582 mA/cm² at 6V, and 5.18 mA/cm² at 8V) of pristine EOD device. The TRPL spectra of pristine and aged (under the normal ambient) Alq3 samples show the decrease of PL decay lifetimes as the aging period increases, which is consistent with the decreased device performances of the further aged devices. The improved device electrical performance of the 6 hrs aged EODs may be attributed to the improved interface properties in the device upon biasing of the pristine device. It is reported that upon aging the luminescent quencher (carbonyl group) formed in the Alq3 is acting as non-radiative recombination center and/or trapping center, quenching the PL lifetimes and the performances of the aged devices. These device results will be useful to improve the efficiency and stability of OLEDs for future lighting and display applications. [ABSTRACT FROM AUTHOR]

White light emitting diodes (WLED) has received much importance due to their vast applications in various sensors, lightning devices and display etc. By mixing certain amount of green, red and blue, white light can have produced. Therefore, we made an attempt to produce a LED application device making use of organic compounds. Hence, we synthesized 2-(6-Fluoro-2-oxo-2H-chromen-4-ylmethoxy)-benzoic acid methyl ester (2‒FBME) coumarin. In this present work the band gap energy is calculated and the photoluminescence spectra of 2‒FBME molecule is studied in different solvents, this result shows the compound can be used to produce the desired wavelength. Hence,2‒FBME possesses high color purity, good CIE chromaticity coordinate, and they would have potential organic light emitting devices (OLED) application, this simple method is used to produce the blue light as blue component can play important role in WLED. [ABSTRACT FROM AUTHOR]

In the present technological world huge demand of white light emitting diodes has received much importance due to their vast applications in various sensors, lightning devices and display etc. The white light can be produced by mixing exact amount of green, blue and red light. Therefore, we made an attempt to produce a LED application making use of organic compounds. Hence, we synthesized 4-Hydroxy-3-[(4-Hydroxy-2-Oxo-2H-Chromen-3-yl) (4- Methoxyphenyl) Methyl]-2H-Chromen-2-One (4,3-Oxo‒HCMM). In this present work we report, the 4,3-Oxo‒HCMM possesses high color purity, good CIE chromaticity coordinate, and they would have potential organic light emitting devices (LED) application, this simple method to produce the blue light as blue component can play important role in WLED. Uv-Vis absorption spectra is used to determine the optical energy bandgap Eg, andfrom the photoluminescence spectra duality nature of wavelengths for4,3-Oxo‒HCMM molecule in different solvents is obtained due to solvation effect, this result shows a simple extraction of dye in different solvents which can be used to produce the desired wavelength. [ABSTRACT FROM AUTHOR]

Despite being efficient electron injection for the organic light-emitting diode, sub-nanometer ultrathin layer of lithium fluoride requires deposition at high temperature and precise layer thickness. Nontoxic organometallic compounds such as lithium stearate and sodium stearate are tested for electron-injection alternatives, which can be deposited at lower temperatures. In this work, OLEDs with lithium or sodium stearates are found to perform better than the lithium fluoride as electron injection. These devices also manage to achieve 90% maximum luminance and power efficiencies over a broader range of 1.5 - 4.5 nm thick of lithium stearate and 2.5 – 4.0 nm thick of sodium stearate. [ABSTRACT FROM AUTHOR]

Highly soluble and violet light emitting 1,4-Bis(benzimidazole-1-yl)benzene (BBI) was investigated theoretically and experimentally. Thin films of BBI compound were prepared using spin coating technique onto glass, quartz and silicon substrate and characterized for their structural and photo-physical properties. UV-Visible absorption studies showed that BBI molecule exhibited absorption in UV region. BBI molecules showed violet emission in solution as well as solid state form. [ABSTRACT FROM AUTHOR]

Recent investigations of the promising materials for optoelectronic have been demonstrated by introducing n-type inorganic material into conjugated polymer. Morphology, optical and electrical of nanocomposites thin films based on poly[2-methoxy-5-(2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and zinc oxide (ZnO) nanotetrapods with various ZnO composition (0 wt% to 0.4 wt%) have been investigated. The MEH-PPV: ZnO nanocomposite thin film was deposited using spin-coating method. Surface morphology was characterized using field emission scanning electron microscopy and shows the uniform dispersion of MEH-PPV and ZnO phases for sample deposited at 0.2 wt%. The photoluminescence (PL) spectra shows the visible emission intensities increased when the ZnO composition increased. The current-voltage (I-V) measurement shows the highest conductivity of nanocomposite thin film deposited at 0.2 wt% of ZnO is 7.40 × 10−1 S. cm−1. This study will provide better performance and suitable for optoelectronic device especially OLEDs application. [ABSTRACT FROM AUTHOR]

Organic light emitting diode (OLED) display technology has demonstrated high efficiency and brightness, is leading to a strong commercial interest. One of the remaining problems with the OLED technology is efficiency and colour saturation. The efficiency of OLED devices can be improved by doping the host organic layer with a suitable phosphorescent material in the emissive layer. We have synthesized a Schiff base zinc metal complex for OLEDs applications. Metal complex was characterized by FTIR, HNMR technique. PL emission spectra were recorded by keeping excitation wavelength fixed at 240 nm. A strong intense emission peak was observed at 410 nm. CIE chromaticity colour coordinates were observed at x =0.239 & y = 0.159. HOMO/LUMO energy gap were found to be −0.223 and −0.067 respectively for prepared zinc metal complex. It could be considered as a good light emitting phosphor material for possible application as emissive layer in OLEDs. [ABSTRACT FROM AUTHOR]

2,4-bis{f3-(9H-carbazol-9-yl)-9H-carbazol-9-yl}-6-phenyl-1,3,5-triazine (CC2TA) is a triazine derivatives in which the acceptor phenyltriazine unit is used as the central skeleton and donor bicarbazole units are bonded to both ends of the skeleton. Molecular orbital calculations exhibit that the HOMO and LUMO are locally allocated chiefly in the bicarbazole and phenyltriazine units, respectively. There are a class of organic molecules and polymers which exhibit semiconductor behavior because of nearly free conjugate π-electrons. Hopping of these electrons in molecules forms different excited singlet and triplet states named as excitons. Some of these organic molecules can be set to emit photons by triplet-singlet excitonic transition via a process called Thermally Activated Delayed Fluorescence (TADF) which is exploited for designing the Organic Light Emitting diode (OLED.) CC2TA is one of these reported noble metal-free TADF molecules which offers unique opto electronic properties arising from the reverse intersystem crossing between the lowest singlet (S) and triplet (T) excited states. Its ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T→S) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic device. In the present study, the CC2TA compounds have been taken up for the investigation of various optoelectronic properties including the thermally activated delayed fluorescence (TADF) by using the Koopmans Method and Density Functional Theory. The present study discusses the utility of the CC2TA organic semiconductor as a suitable TADF material essential for developing an efficient Organic Light Emitting Diode (OLED). [ABSTRACT FROM AUTHOR]

There are a class of organic molecules and polymers which exhibit semiconductor behavior because of nearly free conjugate π-electrons. Hopping of these electrons in molecules forms different excited singlet and triplet states named as excitons. Some of these organic molecules can be set to emit photons by triplet-singlet excitonic transition via a process called Thermally Activated Delayed Fluorescence (TADF) which is exploited for designing the Organic Light Emitting diode (OLED.) Spiro-CN (spirobifluorene skeletons) Spiro is one of these reported noble metal-free TADF molecules which offers unique optical and electronic properties arising from the efficient transition and reverse intersystem crossing between the lowest singlet (S) and triplet (T) excited states. Its ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T→S) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic device. In the present study, the Spiro-CN compounds have been taken up for the investigation of various optoelectronic properties including the thermally activated delayed fluorescence (TADF) by using the Koopmans Method and Density Functional Theory. The present study discusses the utility of the Spiro-CN organic semiconductor as a suitable TADF material essential for developing an efficient Organic Light Emitting Diode (OLED). [ABSTRACT FROM AUTHOR]

In current scenario, the organic materials have given a revolutionary evolution in the electronics industry. As, the organic light emitting diodes (OLEDs) have almost replaced the conventional technologies due to the use of organic based materials. However, the next generations OLEDs are intensively desired nowadays for high definition display technology. There are various concern involved in the successful design of OLEDs. Electrodes are one of the electrical conductors, which play a vital role in the construction of OLEDs. The performance of OLED is majorly affected by the material used for electrodes. Due to the requirement of transparent, flexible and inexpensive anodes in bottom emissive OLEDs, ITO was replaced by graphene material. Graphene is a single layer 2-dimensional transparent carbon allotrope which showed prodigious potential to escalate the device performance. Although graphene demonstrated impressive characteristics in various applications, it showed unfavorable work function for many other devices. Thus, derivative materials of graphene such as graphene oxide, graphane and β – graphdiyne were synthesized by several researchers. By comparing graphene and its derivatives as an anode of OLEDs, it has been found that graphene oxide showed the preeminent performance among all. In this paper, all the comparisons are investigated by using a standard device constructed by piling layers of anode/ m_MTDATA/ NPB/ Alq3: QAD/ Alq3/ cathode in TCAD ATLAS device simulator. [ABSTRACT FROM AUTHOR]

In this paper, we present the development of OLEDs using organophosphorus derivatives as emitters. In this study, we were able to show that the structural variations carried out on phospholes, phosphinines and phosphepines (functionalization of the phosphorus atom, nature of the substituents) make it possible to modulate the emission wavelengths and, thus, the emission colour of the diodes. Using this concept, we were able to develop TADF and chiral organophosphorus emitters and hybrids emitting at different wavelengths which can be used for the development of OLEDs. The diode structures used are simple and provide high external quantum yields. [ABSTRACT FROM AUTHOR]

Transparent conducting electrodes are key components of optoelectronic devices, such as touch screens, organic light emitting diodes (OLEDs) and solar cells. Recent market surveys have shown that the demands for these devices are rapidly growing at a tremendous rate. Semiconducting oxides, in particular indium tin oxide (ITO) are the material of choice for transparent conducting electrodes. However, these conventional oxides are typically brittle, which limits their applicability in flexible electronics. Metal nanowires, e.g. copper (Cu) nanowires, are considered as the best candidate as substitute for ITO due to their excellent mechanical and electrical properties. In this paper, ultralong copper (Cu) nanowires with were successfully prepared by hydrothermal growth at 50-80q C for 1 h. Ethylenediamine was employed as the structure-directing agents, while hydrazine was used as the reductant. In situ mixed potential measurement was also carried out to monitor Cu deposition. Higher temperature shifted the mixed potential negatively, leading to thicker Cu nanowires. Transparent conducting electrode, with a sheet resistance of 197 Ω sq-1 at an optical transmittance of around 61 %, was fabricated with the Cu nanowire ink. [ABSTRACT FROM AUTHOR]

This tool demonstration describes GEMMA, a tool aimed at optimizing the colors used by Android apps, with the goal of reducing the energy consumption on (AM)OLED displays while keeping the user interface visually attractive for end-users. GEMMA has been developed as a distributed architecture to ensure scalability. It is composed of a Web-based client and processing nodes that are capable of analyzing multiple requests (apps) concurrently. The underlying approach makes use of power models, color theory, and multi-objective genetic algorithms. The empirical evaluation of GEMMA indicated its ability to reduce energy consumption while producing color combinations pleasant enough for the users. Also, a qualitative analysis conducted with app developers highlighted the potential applicability of the tool in an industrial context. [ABSTRACT FROM AUTHOR]

Even with the adoption of the latest OLED technology, the display panel remains one of the most power-hungry components in smartphones. Existing attempts for OLED power optimization have mainly focused on modifying the content that is shown on the display during the playback phase, requiring significant overhead in terms of image analysis and modification. While such methods are effective, they overlook opportunities present during the camera recording phase, where utilization of already determined camera parameters could reduce or eliminate the image processing overhead. Hence, we proposed MORPh, a cross-layer optimization system for OLED.We first analyze three fundamental parameters extracted from the smartphone camera and their impact on OLED power consumption and visual quality. We then define corresponding metrics to assess power optimization potentials, and propose a set of algorithms that optimize camera recording to be more OLED friendly. Finally, the proposed schemes are realized as part of a video recording and playback application on an existing Android smartphone. The experiments results indicate power saving of 7.3%∼39.7%, and 20.3% on average while maintaining perceived visual quality. [ABSTRACT FROM AUTHOR]

Polymers containing pendent 3-(2-phenylvinyl)carbazole moieties have been synthesized by the multi-step synthetic route. The polymers represent materials of high thermal stability with initial thermal degradation temperatures exceeding 370 °C. The glass transition temperatures of the amorphous materials were in the rage of 56-65 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of about 5.6 eV. Holetransporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter. The device containing hole-transporting layers of poly{9-[6-(3-methyloxetan-3-ylmethoxy)hexyl]-3-(2-phenylvinyl)carbazole} exhibited the best overall performance with a maximum photometric efficiency of about 4.0 cd/A and maximum brightness exceeding 6430 cd/m2. [ABSTRACT FROM AUTHOR]

Recent investigations of the promising materials for optoelectronic have been demonstrated by introducing ntype inorganic material into conjugated polymer. The optical and electrical of nanocomposite films based on poly[2- methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and zinc oxide (ZnO) nanostructured of various deposition layers (1 to 3 layers) have been investigated. The MEH-PPV: ZnO nanocomposite films were deposited using spin-coating technique. The surface morphology nanocomposite films were characterized using field emission scanning electron microscope. From surface profiler measurement, we found that the thickness of nanocomposite films increased as deposition time increased. The optical properties were measured using photoluminescence spectroscope. The photoluminescence (PL) spectra showed that two deposition layers is the highest intensity at visible region (green emission) due to high energy transfer from particles to the polymer. The current density for two layers sample is due to aggregation of conjugated polymer chain hence form excited interchain exciton for optical excitation. This study will provide better performance and suitable for optoelectronic device especially OLEDs application. [ABSTRACT FROM AUTHOR]

The various composition of ZnAlQ5 such as Zn1.5Al0.5Q5, Zn1Al1Q5, Zn0.5Al1.5Q5 organic phosphors were prepared via simple cost effective co-precipitation method. The FTIR, SEM, photoluminescence analysis of the prepared phosphors were reported. ZnQ2 and AlQ3 were also prepared by similar method and their properties were compared with different composition of ZnAlQ5. The structural elucidation in the form of stretching frequencies of chemical bonds of the prepared phosphor was carried out using Fourier Transform Infrared Spectroscopy (FTIR). The stretching frequency analysis confirms the formation of prepared phosphor materials. The SEM analysis shows the surface morphological behavior of prepared phosphor materials. Greenish photoluminescence were observed at 505 to 510 nm for the different composition of ZnAlQ5,in which Zn1.5Al0.5Q5 shows maximum luminescence intensity at 505 nm. PL emission of ZnQ2 was observed at 515 nm, while for AlQ3 at 520 nm. The blue shift of 10 nm was observed in Zn1.5Al0.5Q5 due to modification of energy level due to presence of Zn2+ and Al3+. The enhancement in PL intensity was observed in Zn1.5Al0.5Q5 compared to the other composition due to transfer of energy between Zn2+ and quinolate complex. Optical properties of the prepared materials were evaluated for possible applications in organic light emitting devices (OLED). [ABSTRACT FROM AUTHOR]

Conjugated polymers are a novel class of materials has been extensively used in optoelectronic devices. Well-known PPV derivative Poly [2-methoxy-5-(2-ethylhexyl-1,4-phenylenevinylene] (MEH-PPV) have a wide applications such as organic light emitting diodes OLED, organic emitting transistor OLET, photovoltaic and organic solar cells. This document focuses on the electronic and optical properties of MEH-PPV and their applications in different optoelectronic devices based on hybrid polymer-semiconductor materials. In this work we studied theoretically the electronic and optical properties of the polymer MEH-PPV using the FP-LAPW calculation method implemented in the wien2k code. The results were determined in the context of the theory of density functional (DFT) made in the approximation of GGA+mBJ. We find our calculated results in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

Transport through thin organic amorphous films, utilized in OLEDs and OPVs, has been a challenge to model by using ab-initio methods. Charge carrier mobility depends strongly on the disorder strength and reorganization energy, both of which are significantly affected by the details in environment of each molecule. Here we present a multi-scale approach to describe carrier mobility in which the materials morphology is generated using DEPOSIT, a Monte Carlo based atomistic simulation approach, or, alternatively by molecular dynamics calculations performed with GROMACS. From this morphology we extract the material specific hopping rates, as well as the on-site energies using a fully selfconsistent embedding approach to compute the electronic structure parameters, which are then used in an analytic expression for the carrier mobility. We apply this strategy to compute the carrier mobility for a set of widely studied molecules and obtain good agreement between experiment and theory varying over several orders of magnitude in the mobility without any freely adjustable parameters. The work focuses on the quantum mechanical step of the multi-scale workflow, explains the concept along with the recently published workflow optimization, which combines density functional with semi-empirical tight binding approaches. This is followed by discussion on the analytic formula and its agreement with established percolation fits as well as kinetic Monte Carlo numerical approaches. Finally, we skatch an unified multi-disciplinary approach that integrates materials science simulation and high performance computing, developed within EU project MMM@HPC. [ABSTRACT FROM AUTHOR]

Transport through thin organic amorphous films, utilized in OLEDs and OPVs, has been a challenge to model by using ab-initio methods. Charge carrier mobility depends strongly on the disorder strength and reorganization energy, both of which are significantly affected by the details in environment of each molecule. Here we present a multi-scale approach to describe carrier mobility in which the materials morphology is generated using DEPOSIT, a Monte Carlo based atomistic simulation approach, or, alternatively by molecular dynamics calculations performed with GROMACS. From this morphology we extract the material specific hopping rates, as well as the on-site energies using a fully selfconsistent embedding approach to compute the electronic structure parameters, which are then used in an analytic expression for the carrier mobility. We apply this strategy to compute the carrier mobility for a set of widely studied molecules and obtain good agreement between experiment and theory varying over several orders of magnitude in the mobility without any freely adjustable parameters. The work focuses on the quantum mechanical step of the multi-scale workflow, explains the concept along with the recently published workflow optimization, which combines density functional with semi-empirical tight binding approaches. This is followed by discussion on the analytic formula and its agreement with established percolation fits as well as kinetic Monte Carlo numerical approaches. Finally, we skatch an unified multi-disciplinary approach that integrates materials science simulation and high performance computing, developed within EU project MMM@HPC. [ABSTRACT FROM AUTHOR]

In this research, study on the transformation of N,N-diphenylamine (DPA) using iodine (I2) utilizing solid state Microwave Assisted Organic Synthesis (MAOS) method has been carried out. The reaction was performed by variations of three parameters namely the mole of reagents, the amount and type of solid support (alumina/Al2O3), and the reaction conditions. Experimental results showed that neutral-alumina was a better solid support than basic-alumina. The optimum temperature for the reaction was approximately at 125-133 °C with reaction time of 15 minutes and microwave reactor power at 500-600 W. The separation of the yellowish green product solution with preparative Thin Layer Chromatography (TLC) method using n-hexane:ethyl acetate = 4:1 (v/v) as eluent yielded two fractions (I and II) and both fractions can undergo fluorescence under 365 nm UV light. Based on the LC chromatogram with methanol:water = 95:5 (v/v) as eluent and its corresponding mass spectra (ESI+), fraction I contained three compounds, which were tetracarbazole A, triphenylamine, and impurities in the form of plasticizer such as bis(2-ethylhexyl) phthalate. Fraction II also contained three compounds, which were tetracarbazole C, tetraphenylhydrazine, and plasticizer such as bis(2-ethylhexyl) phthalate. Both FT-IR (KBr disks) and NMR (500 MHz, CDCl3) spectra of fraction I and II confirmed the aromatic amine groups in those compounds. The observed fluorescence colors of fraction I and II were violet and violetblue, respectively. Based on their structures and fluorescence characters, the compounds in fraction I and II have the potential to be used as Organic Light Emitting Diode (OLED) compound precursors. [ABSTRACT FROM AUTHOR]

'SimOLED' simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq3) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO/HTM (15 nm)/Mixed host (70 nm)/ETM (10 nm)/Al, are stimulated with ratios TPD:Alq3 of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate. [ABSTRACT FROM AUTHOR]

Flows of gas through nozzles with abrupt changes in cross-sectional area are often encountered in practice. In our case such nozzles are used as short length diffuser for producing a layer of organic light-emitting diodes. A hybrid Navier-Stokes/Direct SimulationMonte Carlo simulation is necessary here due to the strong decrease in pressure in the system related to an increase in the Knudsen number. Two popular software tools were coupled. For the domain, where the continuum theory is valid, ANSYS Fluent was chosen, which is one of the world wide leading simulation software for Navier-Stokes simulations. The open source CFD toolbox OpenFOAM includes a widely used Direct Simulation Monte Carlo (DSMC) solver. We coupled both solvers doing a one-shot NS-simulation in the whole domain and de.ned the boundary to the DSMC subdomain manually. Data are exchanged using Dirichlet-Dirichlet type boundary conditions. Our implementation was validated by comparing the results with two experiments. In this paper we describe our implementation and the test scenarios. It is shown that we get a very good agreement between the simulation and the experimental results. [ABSTRACT FROM AUTHOR]

The effects of supplemental UV-A LED lighting on growth and antioxidant properties of two varieties of basil (Ocimum basilicum L.) microgreens were determined. Purple-leaf 'Dark Opal' and green-leaf 'Sweet Genovese' basils were grown in greenhouse (14 days, 22/18 ± 2 °C day/night temperature, 40 ± 5% a relative air humidity) during winter season. The main lighting system (HPS lamps and natural daylight) was supplemented with ~13.0 μmol m-2 s-1 flux of UV-A 390 nm, and a total PPFD was ~125 μmol m-2 s-1 (16 h photoperiod) for 1 or 7 days before harvest, or entire growth period. 14 days. The results revealed that the influence of UV-A on growth and antioxidant properties depended on basil variety and duration of irradiation. Generally, UV-A irradiation for 7 days significantly (P ≤ 0.05) inhibited growth and hypocotyl elongation of green-leaf basils, and for 14 days of both basil varieties. No significant differences on leaf chlorophyll index were determined. However, leaf flavonol index significantly increased in green-leaf basils after 7 and 14 days UV-A irradiation. The total phenols ant anthocyanin contents significantly decreased after 1 day UV-A irradiation in purple-leaf basils, and the continuous decrease following UV-A irradiation for 7 or 14 days was determined. In addition, UV-A irradiation had negative effects on ABTS radical activity in purple-leaf basils; however, the significantly higher ABTS radical scavenging activity after UV-A irradiation for 1 or 7 days in green-leaf basils were determined. UV-A influenced higher ascorbic acid synthesis in purple-leaf basils after 7 days irradiation, or after 14 days irradiation in both basil varieties. In summary, the supplemental UV-A LED lighting allows to protect basil microgreens from hypocotyl elongation, and enhances antioxidant properties in green-leaf basils. Purple-leaf basils showed to be more sensitive to UV-A irradiation, and less positive effects on antioxidant properties were determined. [ABSTRACT FROM AUTHOR]

We demonstrate the improved electroluminescence (EL) in OLEDs by using annealed ITO anode at different temperatures under the normal ambient. SEM studies show the smooth surface morphology of ITO film upto 300°C and it turned wrinkle kind of structure at 400°C. The hole-only device (HOD) based on ITO annealed at 300°C exhibits the higher hole-current density when compared to pristine ITO based device and it is drastically decreased for 400°C. The higher EL emission intensity was observed for OLEDs using ITO annealed at 300°C and it is drastically decreased for 400°C annealed ITO based device. These results show that the annealing of ITO anode upto 300°C improves the holeinjection in OLEDs, balancing the charge carriers and improving the device performance, whereas the change in surface properties of ITO anode annealed at 400°C in turn alters the ITO/TPD interface leading to the charge imbalance, resulting in the decreased device performances. [ABSTRACT FROM AUTHOR]

In an attempt to overcome the limitations of the presently prevailing transparent conducting electrode (TCE) - indium tin oxide (ITO) - many materials have been considered for replacing ITO. Recently, a novel method has been reported for the synthesis of Au-Ag nanowire (NW) mesh, and tested successfully for organic-light-emitting-diodes (OLEDs). It employs UV-induced reduction of gold- and silver- precursors to form Au-Ag NW mesh. In this report, Au-Ag NW mesh thinfilms are synthesized on glass substrates with an objective for use as facing-electrode for Organic Photovoltaics. Various issues and factors affecting the fabrication-process have been improved, and are also discussed here. The electrode showed good transmitivity, of around 95% (excluding that of glass substrate). The advantage of the technique is its simple processing method and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes. [ABSTRACT FROM AUTHOR]

Tin doped indium oxide films are widely used in transparent conducting coatings such as flat panel displays, crystal displays and in optical devices such as solar cells and organic light emitting diodes due to the high electrical resistivity and optical transparency in the visible region of solar spectrum. The deposition parameters have a commendable influence on the optical and electrical properties of the thin films. In this study, ITO thin films were prepared by RF magnetron sputtering. The properties of the films prepared under varying sputtering power were compared using UV- visible spectrophotometry. Effect of sputtering power on the energy band gap, absorption coefficient and refractive index are investigated. [ABSTRACT FROM AUTHOR]

Organic light-emitting diode (OLED) technology is considered as a promising alternative to mobile displays. This paper explores how to reduce the OLED power consumption by exploiting visual attention. First, we model the problem of OLED image scaling optimization, with the objective of minimizing the power required to display an image without adversely impacting the user's visual experience. Then, we propose an algorithm to solve the fundamental problem, and prove its optimality even without the accurate power model. Finally, based on the algorithm, we consider implementation issues and realize two application scenarios on a commercial OLED mobile tablet. The results of experiments conducted on the tablet with real images demonstrate that the proposed methodology can achieve significant power savings while retaining the visual quality. [ABSTRACT FROM AUTHOR]

While active studies have been conducted to reduce the power consumption of display-related components of mobile devices, previous work has rarely approached the issues without having to deteriorate graphical quality. In this paper, we propose an effective scheme to reduce display energy consumption without compromising user experience. We first define a metric called the content rate from which an appropriate refresh rate is determined for displaying content. The proposed system then sets an optimal refresh rate based on the content rate. Extensive experiments demonstrate that our system effectively reduces the total power in commercial smartphones, yet the display quality is satisfactorily maintained. [ABSTRACT FROM AUTHOR]

Energy transfer between poly (9,9'-di-n-oetyltluorenyI-2.7-diy 1 ) ( PF(3)/TiO2 nanopartieles (MPs), as a donor, and Fluorol 7GA as an acceptor has been studied. The energy transfer parameters were calculated by using mathematical models. The dominant mechanism responsible for the energy transfer between the donor and acceptor molecules was Förster-type, as evidenced by large values of quenching rate constant and critical distance of energy transfer as well as fluorescence quantum yield and excited state lifetime of donor in the presence of acceptor. Moreover, these composites, which were used as an emissive layer in organic light emitting diodes, were investigated in terms of current voltage and electroluminescence spectra. [ABSTRACT FROM AUTHOR]

Thin polyvinylidene fluoride (PVDF) layers were received by spray deposition technique on polyethylene terephthalate substrate and then were polarized with voltages in range of -40V to +40V. The influence of the polarization on the dielectric parameters of PVDF layer was defined by the capacitance - voltage characteristics, which were measured at 1kHz and 100kHz. [ABSTRACT FROM AUTHOR]

The influence of the mechanical bending on flexible screen-printed organic light emitting devices upon their electrical properties has been examined. Our measurements showed that flexible printed coatings can be bent to small radii (5 mm and 2.5 mm) of curvature and still function, despite the increase of the electrical resistance of the electrodes from 45 to 62.1 Ohms/sq. This is ascribed to the mixture of two classes organic compounds (low molecular weight and polymeric) in suitable ratio, which guarantee high adhesion and stability against strain. Device failure is caused mainly by the transparent indium tin oxide (ITO) electrode that is not resistant to continuous bending at radius 5 mm, as well as to repeated bending over 2 000 that lead to cracks occurring. Internal stress induced in organic electroluminescent layers with different thickness was determined to be in the range |1|-|7| MPa, based on the radius of curvature. Current-voltage characteristics clearly show the limit of bending, at which current flow stops, because of electrodes degradation. [ABSTRACT FROM AUTHOR]

Transport properties of electrons and holes were investigated not only in a anthracenecontaining poly(p-phenylene-ethynylene)- alt - poly(p-phenylene-vinylene) (PPE-PPV) polymer (AnE-PVstat) light emitting diodes (OLED) but also in an ITO/Ag/polymer/Ag electron and ITO/PEDOT:PSS/polymer/Au hole only devices. Mobility of injected carriers followed the Poole-Frenkel type conduction mechanism and distinguished in the frequency range due to the difference of transit times in admittance measurement. Beginning of light output took place at the turn-on voltage (or flat band voltage), 1.8 V, which was the difference of energy band gap of polymer and two barrier offsets between metals and polymer. [ABSTRACT FROM AUTHOR]

We developed a multi-color microfluidic organic light emitting device, which consists of liquid organic light emitting diodes (OLEDs) and electrochemiluminescence (ECL) devices. A 3 × 3 matrix of emitting pixels was fabricated in SU-8 microchannels sandwiched between polyethylene naphthalate (PEN) and glass substrates with indium tin oxide (ITO) anode and cathode pairs. Liquid organic semiconductor and ECL solutions as liquid emitters were injected into the microchannels. The electroluminescence (EL) and ECL were successfully obtained at the emitting pixels in the microchannels. The proposed structure can be applicable for multi-color liquid-based display. [ABSTRACT FROM PUBLISHER]

A simple and high-throughput fabrication of large-area and multilayer polymer film structures was developed and applied for microfluidic organic light emitting diodes (OLED). We employed following three distinguished technologies, a) screen-printing technique for transparent electrodes, b) novel belt-transfer exposure technology for SU-8 microchannels, and c) heterogeneous low temperature bonding technology using self-assembly monolayer. A Liquid organic semiconductor as a liquid emitter was injected to each microchannel and photoluminescence and electroluminescence were obtained not only in a straight state, but also in a bending state. This large-area flexible microfluidic structure for OLED is applicable to nondisposable posters or displays which can be adopted around the curved surfaces of the various structures. [ABSTRACT FROM PUBLISHER]