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The unique four-level photocycle characteristics of excited-state intramolecular proton transfer (ESIPT) materials enable population inversion and large spectral separation between absorption and emission through their respective enol and keto forms. This leads to minimal or no self-absorption losses, a favorable feature in acting as an optical gain medium. While conventional ESIPT materials with an enol-keto tautomerism process are widely known, zwitterionic ESIPT materials, particularly those with high photoluminescence, are scarce. Facilitated by the synthesis and characterization of a new family of 2-hydroxyphenyl benzothiazole (HBT) with fluorene substituents

The stellar optoelectronic properties of metal halide perovskites provide enormous promise for next-generation optical devices with excellent conversion efficiencies and lower manufacturing costs. However, there is a long-standing ambiguity as to whether the perovskite surface/interface (e.g. structure, charge transfer or source of off-target recombination) or bulk properties are the more determining factor in device performance. We fabricated an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualised the property-performance landscape. Our findings reveal that the interface is the primary determinant of the crystal phases, optoelectronic quality, and stability of CsPbI3. In particular, the presence of a diffusion "alloying" layer is discovered to be critical for passivating surface traps, and beneficially altering the energy landscape of crystal phases. However, high-temperature sintering results in the promotion of a non-stoichiometric perovskite and excess traps at the interface, despite the short-range structure of halide is retained within the alloying layer. By shedding light on functional hetero-interfaces, our research offers the key factors for engineering high-performance perovskite devices.

Solution-processed hyperfluorescent red organic light-emitting diodes with external quantum efficiencies of 15.3% was achieved by using cibalackrot as the fluorescent emitter, where attaching tert-butyl groups to the assistant host significantly contributes to device performance.

In this work, white light emission from the blend of a hole transport material, 4,4′-cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), and an electron transport material, 2,2′,2″-(1,3...

N-Heterocyclic carbene (NHC) cyclometalated gold(III) complexes remain very scarce and therefore their photophysical properties remain currently underexplored. Moreover, gold(III) complexes emitting in the blue region of the electromagnetic spectrum are rare. In this work, a series of four phosphorescent gold(III) complexes was investigated bearing four different NHC monocyclometalated (C C*)-type ligands and a dianionic (N N)-type ancillary ligand ((N N)= 5,5'-(propane-2,2-diyl)bis(3-(trifluoromethyl)-1H-pyrazole) (mepzH(2))). The complexes exhibit strong phosphorescence when doped in poly(methyl methacrylate) (PMMA) at room temperature, which were systematically tuned from sky-blue [lambda(PL)= 456 nm, CIE coordinates: (0.20, 034)] to green [lambda(PL)= 516 nm, CIE coordinates: (0.31, 0.54)] by varying the monocyclometalated (C C*) ligand framework. The complexes revealed high quantum efficiencies (fPL) of up to 43% and ex- cited-state lifetimes (tau(0)) between 15-266 ms. The radiative rate constant values found for these complexes (k(r)= 10(3)-10(4) s(-1)) are the highest found in comparison to previously known best-performing monocyclometalated gold(III) complexes. Density functional theory (phi(FT)) and time-dependent DFT (TD-DFT) calculations of these complexes further lend support to the excited-state nature of these complexes. The calculations showed a significant contribution of the gold(III) metal center in the lowest unoccupied molecular orbitals (LUMOs) of up to 18%, which was found to be unique for this class of cyclometalated gold(III) complexes. Additionally, organic light-emitting diodes (OLEDs) were fabricated by using a solution process to provide the first insight into the electroluminescent (EL) properties of this new class of gold(III) complexes.

Triplet excitons have been identified as the major obstacle to the realisation of organic laser diodes, as accumulation of triplet excitons leads to significant losses under continuous wave (CW) operation and/or electrical excitation. Here, we report the design and synthesis of a solid-state organic triplet quencher, as well as in-depth studies of its dispersion into a solution processable bis-stilbene-based laser dye. By blending the laser dye with 20 wt% of the quencher, negligible effects on the ASE thresholds, but a complete suppression of singlet–triplet annihilation (STA) and a 20-fold increase in excited-state photostability of the laser dye under CW excitation, were achieved. We used small-area OLEDs (0.2 mm2) to demonstrate efficient STA suppression by the quencher in the nanosecond range, supported by simulations to provide insights into the observed STA quenching under electrical excitation. The results demonstrate excellent triplet quenching ability under both optical and electrical excitations in the nanosecond range, coupled with excellent solution processability., Though reducing non-emissive triplet excited-states using quenchers effectively improves organic semiconductor laser diode (OSLD) performance, existing quenchers are not suitable for devices. Here, the authors designed a solid-state triplet quencher for OSLD under optical and electrical excitation.

Hyperfluorescent organic light-emitting diodes (HF-OLEDs) enable a cascading Förster resonance energy transfer (FRET) from a suitable thermally activated delayed fluorescent (TADF) assistant host to a fluorescent end-emitter to give efficient OLEDs with relatively narrowed electroluminescence compared to TADF-OLEDs. Efficient HF-OLEDs require optimal FRET with minimum triplet diffusion via Dexter-type energy transfer (DET) from the TADF assistant host to the fluorescent end-emitter. To hinder DET, steric protection of the end-emitters has been proposed to disrupt triplet energy transfer. In this work, the first HF-OLEDs based on structurally well-defined macromolecules, dendrimers is reported. The dendrimers contain new highly twisted dendrons attached to a Cibalackrot core, resulting in high solubility in organic solvents. HF-OLEDs based on dendrimer blend films are fabricated to show external quantum efficiencies of10% at 100 cd m

Lead halide perovskite (LHP) semiconductors show exceptional optoelectronic properties. Barriers for their applications, however, lie in their polymorphism, instability to polar solvents, phase segregation, and susceptibility to the leaching of lead ions. We report a family of scalable composites fabricated through liquid-phase sintering of LHPs and metal-organic framework glasses. The glass acts as a matrix for LHPs, effectively stabilizing nonequilibrium perovskite phases through interfacial interactions. These interactions also passivate LHP surface defects and impart bright, narrow-band photoluminescence with a wide gamut for creating white light-emitting diodes (LEDs). The processable composites show high stability against immersion in water and organic solvents as well as exposure to heat, light, air, and ambient humidity. These properties, together with their lead self-sequestration capability, can enable breakthrough applications for LHPs.

A new molecular design for organic semiconductor laser dyes showing excellent optical properties and high robustness is disclosed in this work. The suitability of a furan moiety for increasing the ...

The synthesis, characterization, and spectroscopic investigations of a new solution‐processable N‐styrylcarbazole‐linked tetraphenylethylene (TPE) derivative (TPE‐BCzS) are reported, exhibiting green–orange emission. While the material displays weak photoluminescence (PL) in solution with a low PL quantum yield (PLQY of 4 ± 0.2%), significant PL enhancement in neat‐film PLQY (55 ± 8%) is observed. Studies using steady‐state spectroscopy, and femtosecond and nanosecond transient absorption spectroscopy reveal details of the excited‐state dynamics, consisting of the Franck–Condon (FC) state, nonradiative conformational relaxation, and formation and decay of the triplet excited state generated via intersystem crossing (ISC) upon ultrafast photoexcitation. Solution‐processed organic light‐emitting diodes (OLEDs) based on TPE‐BCzS display maximum external quantum efficiencies of 1.8% and 1.7% for neat and blend films (20 wt% in a 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl host), approaching the theoretical efficiency limit for the determined PLQYs of the films. While TPE materials are typically associated with aggregation‐induced emission, it is reported that the enhanced PLQYs in the solid state are due to restriction of structural relaxations in the solid state and not due to the commonly misunderstood aggregation effect.

In this work, we describe the design and synthesis of a novel, organic emissive small donor–acceptor–donor molecule, 3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-9H-fluoren-9-one, and its incorporation into functional organic light-emitting diode (OLED) devices. The molecule was developed through a three-step procedure with high yields using low-cost and commercially available materials. Photophysical analysis shows emission from both locally excited (LE) and intramolecular charge transfer (ICT) fluorescent states, leading to broad emission spectra with a high solution photoluminescence quantum yield of 73%. Time resolved and temperature dependent photoluminescence measurements were utilized to obtain insights about emission mechanism from LE and ICT states. The presence of broad emission was further confirmed using density functional theory calculations. After optimal design and selection of the film thickness and host matrix, an OLED using a solution-processed host: dopant emissive layer with 10 wt% dopant exhibited a maximum current efficiency, power efficiency and external quantum efficiency of 2.6 cd A−1, 2.5 lm W−1 and 1.5%, respectively.

With wider application and technical improvement of imaging the discovery of adrenal incidentalomas (AI) has been skyrocketing. AI need to be investigated for evidence of hormonal hypersecretion and malignancy, and this causes a considerable use of health resources and potential medicalisation. In the "no-need-to-see" process, the clinical assessment of the citizen will only take place, if the diagnostic tests are abnormal. In this review, we examine the predictive values of imaging and paraclinical testing and argue, that normal test results in people without extra-adrenal cancer exclude disease.

While significant progress has been made over last few years in the field of organic solid-state lasers, achieving lasing action from organic semiconductors under electrical excitation still remains a big challenge. One of the major barriers towards electrically pumped organic lasers are optical losses due to triplet excitons. In this work, we report both experimental and theoretical results that confirm positive contribution of triplet excitons for the scope of electrically driven organic laser. We studied a model fluorescence material, 9-(9-phenylcarbazole-3-yl)-10(naphthalene-1-yl) anthracene and reveals that the threshold current densities required to achieve lasing emission under electrical injection can be significantly reduced with the aid of triplet-triplet exciton upconversion processes. Furthermore, we demonstrate that, to achieve the best performance, the singlet-triplet exciton annihilation must be minimized. These results are unprecedented and provide a pathway towards development of new class of triplet-triplet upconversion materials for injection laser.

Electrical pumping of organic semiconductor devices involves charge injection, transport, device on/off dynamics, exciton formation and annihilation processes. A comprehensive model analysing those entwined processes together is most helpful in determining the dominating loss pathways. In this paper, we report experimental and theoretical results of Super Yellow (Poly(p-phenylene vinylene) co-polymer) organic light emitting diodes operating at high current density under high voltage nanosecond pulses. We demonstrate complete exciton and charge carrier dynamics of devices, starting from charge injection to light emission, in a time scale spanning from the sub-ns to microsecond region, and compare results with optical pumping. The experimental data is accurately replicated by simulation, which provides a robust test platform for any organic materials. The universality of our model is successfully demonstrated by its application to three other laser active materials. The findings provide a tool to narrow the search for material and device designs for injection lasing., Though efforts toward electrically-pumped lasers based on simple organic light-emitting diode (OLED) structures have been reported, a comprehensive model is needed to elucidate key optoelectronic processes. Here, the authors report a model describing OLED operation under high current densities.

A novel solution processable organic semiconductor dye, 9,9'-(((1E,1'E)-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis(ethene-2,1-diyl))bis(4,1-phenylene))bis(9H-carbazole) (BSFCz) was synthesized and investigated in terms of its amplified spontaneous emission (ASE) and surface emission laser properties under optical excitation. Films of BSFCz, which were blended with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) at 6 wt.% with solution processing, had a low ASE threshold of 1.1 μJ cm−2 and surface emission laser threshold of 0.9 μJ cm−2 with second-order distributed feedback structure. Moreover, our BSFCz-based devices exhibited quasi-continuous-wave lasing with good stability up to 10 ms. To the best of our knowledge, this is the first ever demonstration of solution-processed organic lasers, which can work under the quasi-continuous wave regime.

External quantum efficiency (EQE) roll-off under high current injection has been one of the major limiting factors toward the development of organic semiconductor laser diodes (OSLDs). While significant progress in this regard has been made on organic semiconductors (OSCs) emitting in the blue-green region of the visible spectrum, OSCs with longer wavelength emission (600 nm) have fallen behind in both material development and the advancement in device architectures suitable for the realization of OSLDs. Therefore, to make simultaneous incremental advancements, a host-guest system comprising of a high performing poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) polymer and an efficient small molecule laser dye, dithiophenyl diketopyrrolopyrrole (DT-DPP), is used. This combination provides an extremely low amplified spontaneous emission threshold of 4.2 µJ cm

The search for new classes of efficient electroluminescent organic laser dyes with low amplified spontaneous emission (ASE) threshold (Eth) and low optical losses is crucial toward the realization of organic injection lasers. In this work, we report in-depth studies of an organic semiconducting laser dye, benzo[d]thiazol-2-yl)-5-(9H-carbazol-9-yl)phenol (HBT-Cz), and compare the photophysical study with its parent HBT dye. While HBT is not laser-active in solution, the carbazole derivatized dye (i.e., HBT-Cz) showed a low solution ASE threshold of 21 mJ/cm2, which is comparable to a common high-performing commercial laser dye, Rhodamine 6G (Rh-6G). HBT-Cz also exhibited a low film ASE threshold of 2.4 μJ/cm2 with a low optical loss coefficient of 1.5 cm–1, which is the lowest waveguide loss coefficient reported for solution-processed organic semiconductors. Organic light-emitting diodes based on this material showed a high maximum EQE of 1.9%, which is close to the theoretical EQE limit of the emitter, an...

Browsers are widely used on personal computers, laptops and mobile devices. In this chapter, we seek to determine and compare which forensic artifacts can be recovered from Google Chrome, Mozilla Firefox, their respective private modes, and TOR. Our analysis was primarily conducted using FTK in order to replicate the process and abilities of a digital forensics lab with limited resources. After identical data generation across all browsers and modes of browsing in a controlled virtual environment, forensic images were captured then analyzed. This research not only extends the current field of digital forensics for which artifacts can be found in which locations, but also confirms various claims in regards to the privacy of private browsing modes. As expected, all data was recovered from regular browsing modes, very minimal data from private browsing, and almost no artifacts from TOR.

The authors are grateful to the Australian Research Council (ARC DP160100700 and DP200103036), Australian Department of Industry, Innovation and Science (AISRF53765), the UK Engineering and Physical Sciences Research Council (Grants EP/M025330/1 and EP/L017008/1), China Scholarship Council and the Rank Prize Funds for financial support. Organic semiconductors possessing tightly bound Frenkel excitons are known to be attractive candidates for demonstrating polariton lasing at room temperature. As polariton lasing can occur without inversion, it is a potential route to very low threshold coherent light sources. However, so far, the thresholds of organic polariton lasers have generally been much higher than those of organic photon lasers. Here this problem has been addressed by investigating two new organic molecules with a structure combining fluorene and carbazole groups. The materials are readily deposited from solution and exhibit high photoluminescence quantum yields, high absorption coefficients, and large radiative decay rates in neat films. Room temperature polariton lasing is realized in both materials with incident thresholds of 13.5 and 9.7 µJ cm−2, corresponding to absorbed thresholds of 3.3 and 2.2 µJ cm−2, respectively. These are the lowest values reported to date for polariton lasing in organic semiconductor materials, and approach typical values for organic photon lasers. The step-like power dependent blue-shift of polariton modes indicates an interplay between different depletion channels of the exciton reservoir. This work brings practical room temperature polaritonic devices and future realization of electrically driven polariton lasers a step closer. Publisher PDF

Over the years, achieving efficient electroluminescence (EL) while simultaneously having low light amplification thresholds under optical excitation has been the key to progression toward the long-thought objective of electrically pumped organic lasers. While significant progress in this regard has been made for organic semiconductors emitting in the blue–green region of the visible spectrum, organic laser dyes with low-energy emission (>600 nm) still suffer from high amplified spontaneous emission (ASE) thresholds and low external quantum efficiencies (EQEs) in devices. Herein, low ASE thresholds and efficient EL are reported from a solution-processable organic laser dye dithiophenyl diketopyrrolopyrrole (DT-DPP). The ASE threshold of 4 µJ cm at the wavelength of 620 nm is obtained while making constructive use of triplet excitons by doping DT-DPP in a green-emitting host matrix, which exhibits thermally activated delayed fluorescence (TADF). The organic light-emitting diode fabricated from this system gives a high EQE of 7.9% due to the efficient utilization of triplet excitons. Transient EL studies further show that a high reverse intersystem crossing rate is crucial in achieving lasing under electrical pumping from such TADF-assisted fluorescent systems.

Different Manufacturing Processes Optimized by Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) Algorithm are presented in this review paper. The main focus of this review paper is on the optimization of the various manufacturing processes that have been optimized by TOPSIS method. The machining processes that have been considered in this work are Milling, Drilling, Turning, Electric Discharge Machining, Abrasive Jet Machining, Micro Machining, and other advanced types of machining process. The review work on manufacturing processes, on such a large scale was not performed earlier by considering different processes at a time on TOPSIS method, and hence, this review work prepare for the future information at one place for the subsequent researchers, in order to determine their way of research on TOPSIS Algorithm.

Accumulation of triplets under long‐pulse photoexcitation has been the key obstacle to the achievement of long‐pulse lasing activity for organic semiconductor laser dyes. Chihaya Adachi, Ebinazar B. Namdas, Shih‐Chun Lo and co‐workers (article number 2001234) demonstrate the first lasing action under long‐pulse optical excitation from a novel solution processable organic semiconductor laser dye. The negligible spectral overlap between triplet excited‐state absorption and photoluminescence emission, together with high radiative decay rate and high photoluminescence quantum yield, empowers the long‐pulse lasing activity.

High mechanical flexibility and wavelength tunability of organic semiconductor materials have propelled the development of organic semiconductor lasers (OSLs) as a complementary technology to current inorganic lasers. While excellent progress has been made across multiple aspects of OSLs, demonstration of long‐pulse operation [quasi‐continuous wave (qCW) or continuous wave (CW)] lasing has presented significant challenges due to the detrimental accumulation of triplets under long‐pulse photoexcitation and substantial quenching of singlet excitons, arising from singlet‐triplet annihilation (STA). In particular, qCW or CW lasing from solution‐processed OSL materials has not been reported, and thus remains a long‐thought objective in optoelectronic research. Using a novel bis(N‐carbazolylstyryl)‐9,9‐dihexylfluorene (BSFCz), the first solution‐processable organic laser dye demonstrating lasing oscillation in the long‐pulse photoexcitation regime (up to 10 ms pulse width) with a low threshold (420 W cm−2), which in part can be attributed to its negligible spectral overlap between triplet excited‐state absorption and laser emission, is herein reported. Temporal emission profiles below and above the lasing threshold also demonstrate that STA has a negligible effect on emission. These combined observations show BSFCz incur low losses due to triplet excited‐states, leading to extremely small changes in lasing thresholds when moving from pulsed to qCW (>1 ms) excitation.

Organic semiconductor dyes have attracted high interest as laser gain media owing to their judicious features of solution processability, lightweight, high mechanical flexibility, high wavelength-tunability, and low-cost manufacture. In this work, fluorene-carbazolylstyryl hybrids are reported, SFCz and BSTFCz, as new solution processable organic semiconductor laser dyes to show high molar extinction coefficients (up to 1.98 x 10(5)dm(3)mol(-1)cm(-1)), high photoluminescence quantum yields (up to 81 +/- 4%), high radiative decay constants (up to 1.24 x 10(9)s(-1)), and low film amplified spontaneous emission thresholds (down to 0.70 mu J cm(-2)). By using mixed-order distributed feedback laser structures, extremely low lasing threshold of 0.5 mu J cm(-2)is achieved. To elucidate their electroluminescent properties, simple solution-processed organic light-emitting diodes based on the new materials are fabricated to show good external quantum efficiencies (2%) and high brightness (approximate to 2800 cd m(-2)). The results indicate the ease in material synthesis and fabrication enabling solution-processed low-threshold lasing toward future injection laser.

Recent studies have demonstrated that in thermally activated delayed fluorescence (TADF) materials, efficient reverse intersystem crossing occurs from nonradiative triplet exited states to radiative singlet excited states due to a small singlet–triplet energy gap. This reverse intersystem crossing significantly influences exciton annihilation processes and external quantum efficiency roll‐off in TADF based organic light‐emitting diodes (OLEDs). In this work, a comprehensive exciton quenching model is developed for a TADF system to determine singlet–singlet, singlet–triplet, and triplet–triplet annihilation rate constants. A well‐known TADF molecule, 3‐(9,9‐dimethylacridin‐10(9H )‐yl)‐9H ‐xanthen‐9‐one (ACRXTN), is studied under intensity‐dependent optical and electrical pulse excitation. The model shows singlet–singlet annihilation dominates under optically excited decays, whereas singlet–triplet annihilation and triplet–triplet annihilation have strong contribution in electroluminescence decays under electrical pulse excitation. Furthermore, the efficiency roll‐off characteristics of ACRXTN OLEDs at steady state is investigated through simulation. Finally, singlet and triplet diffusion length are calculated from annihilation rate constants.

We report on highly efficient flexible inverted organic solar cells (IOSCs) fabricated by low-temperature solution process on polyethylene terephthalate (PET) substrate. In general, IOSCs have been required to use an annealed (>200 degrees C) zinc oxide (ZnO) as an electron transport layer. However, any twisting of the flexible substrate during heat treatment leads to poor device performance. To overcome this issue, we developed a novel low temperature process for flexible IOSCs using an alcohol-/water-soluble conjugated polymer, namely poly [(9,9-bis(3'-(N, N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) instead of the ZnO. Using this low-temperature process, we successfully demonstrate highly efficient flexible IOSCs that are proven to be capable of the power conversion efficiency (PCE) of 6.17% which retain 96% of its efficiency at a bending radius of R approximate to 5 mm or less. To the best of our knowledge, this PCE 6.17% is the best result among the reported values so far for flexible OSCs fabricated on PET substrate. (C) 2015 Elsevier Ltd. All rights reserved.