Blue organic light-emitting diodes (OLEDs) utilizing triplet-harvesting emitters require the use of high-triplet-energy hosts and blocking layers to confine the triplet excitons to the emitter. The use of these materials poses design challenges, while potentially compromising charge transport and operational stability. Here, we present efficient single-layer blue OLEDs comprising solely of a neat thermally activated delayed fluorescence (TADF) emitter sandwiched between two charge-injecting electrodes, without using high-triplet-energy materials. By further incorporating a narrow-band terminal emitter, we simultaneously improve the charge balance and color purity, realizing pure-blue single-layer hyperfluorescent OLEDs with an external quantum efficiency (EQE) of 21.1% and minimal efficiency roll-off. Analysis of the charge transport reveals that the improvement in charge balance is caused by the offset in ionization energy between the TADF sensitizer and the terminal emitter, slowing down hole transport. Our results demonstrate the feasibility of efficient pure-blue single-layer OLEDs without auxiliary high-triplet-energy materials, featuring a simple design and added stability benefits.

Nanomaterials (NMs) are gradually revolutionizing our world. They are playing an increasingly vital role across various fields, from everyday products to advanced technology. Nanoparticles (NPs) differ from bulk materials due to their high surface-area-to-volume ratio, which significantly influences their physical properties and reactivity. Metal oxide NPs possess unique characteristics, including a tunable band gap, making them suitable for diverse applications. The demand for environmentally friendly synthesis methods is growing, as green approaches offer a sustainable and cost-effective alternative for NP production. While gold and silver NPs have been widely studied, their high-cost limits large-scale applications. In contrast, metal oxide NPs of first-transition-series elements provide a more economical option. This review explores the green synthesis of these NPs and their applications, particularly in antibacterial treatments and water remediation, highlighting their potential as sustainable solutions for environmental and biomedical challenges.

White organic light-emitting diodes (WOLEDs) are promising candidates for next-generation lighting and display technologies. However, conventional WOLED fabrication often relies on complex doping schemes or multiple color stacked emitting layers, complicating device design, and fabrication. Here, a simple approach for fabricating ITO-free WOLEDs with a single-component, using a planar aluminium microcavity, is presented. By engineering the cavity and surface plasmon polariton modes around the emission resonance of the high-efficiency blue thermally activated delayed fluorescence emitter DMAC-DPS, electroluminescence that is spectrally broadened to white light, with a tunable color temperature ranging from 3790 to 5050 K, is achieved. The WOLEDs are top-emitting and reach an external quantum efficiency of >5%. The results are supported by optical simulations and transient emission measurements, providing insights into the emission kinetics.

Modifying the energy landscape of existing molecular emitters is an attractive challenge with favourable outcomes in chemistry and organic optoelectronic research. It has recently been explored through strong light-matter coupling studies where the organic emitters were placed in an optical cavity. Nonetheless, a debate revolves around whether the observed change in the material properties represents novel coupled system dynamics or the unmasking of pre-existing material properties induced by light-matter interactions. Here, for the first time, we examined the effect of strong coupling in polariton organic light-emitting diodes via time-resolved electroluminescence studies. We accompanied our experimental analysis with theoretical fits using a model of coupled rate equations accounting for all major mechanisms that can result in delayed electroluminescence in organic emitters. We found that in our devices the delayed electroluminescence was dominated by emission from trapped charges and this mechanism remained unmodified in the presence of strong coupling.

Improving the performance of organic optoelectronicshas been undervigorous research for decades. Recently, polaritonics has been introducedas a technology that has the potential to improve the optical, electrical,and chemical properties of materials and devices. However, polaritonshave been mainly studied in optical microcavities that are made byvacuum deposition processes, which are costly, unavailable to many,and incompatible with printed optoelectronics methods. Efforts towardthe fabrication of polariton microcavities with solution-processedtechniques have been utterly absent. Herein, we demonstrate for thefirst time strong light-matter coupling and polariton photoluminescencein an organic microcavity consisting of an aluminum mirror and a distributedBragg reflector (DBR) made by sequential dip coating of titanium hydroxide/poly(vinylalcohol) (TiOH/PVA) and Nafion films. To fabricate and develop thesolution-processed DBRs and microcavities, we automatized a dip-coatingdevice that allowed us to produce sub-100 nm films consistently overmany dip-coating cycles. Owning to the solution-based nature of ourDBRs, our results pave the way to the realization of polariton optoelectronicdevices beyond physical deposition methods.

The search for efficient and transparent nonlinear optical (NLO) media has led to the investigation and development of alternative organic optical materials. In this context, a series of new hexylthiotruxene derivatives have been synthesized, and their linear and NLO properties are explored. These truxene derivatives show large NLO absorption due to their C3 symmetry, presence of large hyperpolarizability, and extended π-conjugation. Herein, we show that two-photon absorption and three-photon absorption processes are the main cause of nonlinear absorption in these materials under 5 ns and 100 fs excitations at 532 and 800 nm excitations, respectively. The nonlinear absorption coefficients have high values of 2 to 7.9 × 10–10 m/W in the nanosecond domain and 2.2 to 7.4 × 10–21 m3/W2 in the femtosecond domain. The corresponding nonlinear absorption cross-section (δ) values and the nonlinear susceptibilities were also calculated from the numerically obtained nonlinear absorption coefficient values. Tailored truxene derivative showed an excellent optical limiting threshold of 4.5 J/cm2 and is comparable to or better than most recently reported and benchmark optical limiting materials. Longer alkyl members of the series showed the largest nonlinear absorption in both excitation domains and could be a potential optical limiter.

The use of highly efficient organic emitters based on the thermally activated delayed fluorescence (TADF) concept is interesting due to their 100% internal quantum efficiency. Presented here is a solution deposition method for the fabrication of efficient organic light-emitting diodes (OLEDs) based on a TADF emitter in a simple device structure. This fast, low-cost, and efficient process can be used for all OLED emissive layers that follow the host-guest concept. The fundamental steps are described along with necessary information for further reproduction. The goal to establish a general protocol that can be easily adapted for principal organic emitters currently under study and development.

We report on enhanced nonlinear optical absorption and optical limiting in beta-MnO2 sponge-like nanowire network decorated with Ag nanoparticles excited by nanosecond laser. A simple two-step process is used to prepare the samples. The structure, morphology and the elemental analysis of the prepared samples are studied using x-ray diffraction, field emission scanning electron microscopy and energy-dispersive x-ray spectroscopy. Nonlinear optical absorption properties of the samples in solution is studied using the open aperture Z-scan technique employing 5 ns laser pulses at 532 nm. Nonlinear transmission measurements show that beta-MnO2 exhibit weak saturable absorption at low fluence and large optical limiting at high fluence, while upon decoration with Ag particles, Ag/beta-MnO2 shows strong saturable absorption at low fluence and enhanced optical limiting at higher fluence with an optical limiting threshold value three times lower than that of bare beta-MnO2 nanowires. The results indicate that these materials are potentially useful for constructing saturable absorbers and optical limiters.

Simple solution-processed structures of organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) have been demonstrated, but their efficiency and roll-off are still problematic, mainly due to the difficulty in optimizing such device structures. For the first time, solution-processed fabrication of efficient TADF green OLEDs with a simple structure is demonstrated. The emitter 2PXZ-OXD (2,5-bis(4-(10H-phenoxazin-10-yl)phenyl)-1,3,4-oxadiazole) was dispersed in a poly(N-vinylcarbazole)/1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo- 5-yl]benzene (OXD-7) host matrix. Different emitter concentrations (1-10% wt) and different layer thicknesses were applied. Photophysical analysis supports the device structure configuration. The results show a balanced electrical carrier transport, a low turn-on voltage (5 V), an external quantum efficiency (EQE) of 7.5%, and a current efficiency of 16.2 cd/A with a brightness of 7240 cd/m(2). The device exhibited a suppressed roll-off at 1000 cd/m(2) (EQE: 7.15%). Simulations of charge transport properties allowed to explain the results and to optimize, opening interesting frameworks for simple solution-deposited large-area OLEDs.

Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence emitters (TADF) in simple device structures fabricated by solution processing are strongly dependent on a suitable host molecular conformation and morphology. Herein, we report the fabrication of highly efficient yellow-red TADF-based OLEDs via solution processing in a simple, two-organic-layer device structure. The devices were fabricated at different weight concentrations of 5%, 8%, and 10% emitter in an n-/p-type mixed host matrix, and their characteristics were studied. The device performance was compared with different thickness parameters for both the emitting layer (EML) and the electron transport layer (ETL) in various solvents, including chlorobenzene, dichlorobenzene, and chloroform. By optimizing the mixed ratio of EML, yellow-red OLEDs of 2-[4 (diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA) emitter in an n-/p-type host matrix of poly(N-vinylcarbazole):1,3-Bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (PVK:OXD-7) as a blend for the active layer were fabricated. In the best results, the device exhibited a lower turn-on voltage at around 6 V, with an external quantum efficiency (EQE) of 18.44%, current efficiency of 36.71 cd/A, and power efficiency of 14.74 Lm/W for the 8% emitter concentration. The importance of solvent for improving the electrical properties, together with organic layer thickness and host effect for the charge carrier's transport and device characteristics are also discussed.

Discotic liquid crystals (DLCs) are one-dimensional organic semiconducting materials and represent new low cost, rejuvenating materials in optoelectronics. The development of novel supramolecular materials based on liquid crystals (LCs) hybridized with various metallic, semiconducting, and carbon-based materials with optimized functionalities on the nanometer scale attracted much attention in liquid crystal nanoscience. The ability to combine supramolecular liquid crystalline chemistry with nanoscience is very attractive for several reasons. This review focuses on our recent advances in discotic liquid crystal nanoscience. Driven by the self-assembly of both liquid crystals and nanostructures, LC–nanomaterial nanocomposites (LC–NCs) are spontaneously formed through molecular self-organization at the nanometer scale. The careful design of different LC–NCs through enhanced LC properties opened a new era for organic electronics. A brief introduction to LCs is presented with emphasis on DLCs, which is followed by recent developments in the self-assembly of various nanostructures in discotics. We focus on how nanostructures can be self-assembled in such supramolecular materials so that self-organizing functional systems of discotics can be created with tuned physical properties, such as the thermal stability, optoelectronic and dielectric parameters, and response time, in LCs. We conclude this review by discussing the further development of nanoscience with LCs and applications in organic electronics.

Charge balance, concentration quenching, and exciton confinement are the most important factors for realizing the use of thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes. Red-orange organic light-emitting diodes of a TADF emitter 2-[4 (diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA) have been reported by doping in a mixed p-type host system of poly(N-vinylcarbazole) (PVK) and 1,3-bis(N-carbazolyl)benzene (mCP) via solution-processed. We have demonstrated the peak external quantum efficiency of 9.75%, maximum current efficiency of 19.36 cd/A, and power efficiency of 12.17 lm/W along with a CIE coordinate of (0.45, 0.51). The devices were compared with different doping concentrations of TXO-TPA, and a comparative investigation on the effect of the thickness electron transport layer was studied. The results clearly indicated that this solution-processed TXO-TPA device structure is a promising strategy to develop highly efficient but simple OLED structures.

To achieve significant efficiency and low roll-off in thermally activated delayed fluorescence (TADF) material organic light-emitting diodes (OLEDs), it is essential to choose a host that has suitable high triplet energy (T1) and bipolar character to boost the TADF characteristics as a dopant and avoid exciton annihilation. Herein, we present the effect of different host materials on the efficiency of organic light-emitting diodes (OLEDs) based on bis[4-(3,6 dimethoxycarbazole)phenyl]sulfone (DMOC-DPS) deep-blue emitter. The devices with 10 wt.% of an emitter in different electron types of host bis[2-(diphenylphosphino) phenyl] ether oxide (DPEPO), and hole types of host 1,3-bis(N-carbazolyl)benzene (mCP), were fabricated to study the effect on device performance. The results show that an external quantum efficiency (EQE) of 4% and maximum current efficiency (ƞc) up to 5.77 cd/A with high luminescence (lmax) 8185 cd/m2 in DPEPO was achieved, compared to 2.63% EQE, ƞc 4.12 cd/A with lmax 5338 cd/m2 in mCP in a very simple device structure. As a remarkable result, the roll-off is suppressed at 1000 cd/m2, and for maximum brightness, the roll-off is less than 50%. Further general applications are discussed.

In this work, OPVs with an active layer composed by P3HT (poly(3-hexylthiophene)) and PCBM ([6,6]-phenyl-C61- butyric acid methyl ester) was fabricated by spin coating technique and studied after post-thermal annealing. The devices were annealed at temperatures ranging from 150 °C to 175 °C, showing an increase in efficiency at 160 °C, decreasing after. In order to achieve a physical model for this behavior, dc and ac measurements, together morphology analysis was made and correlated. Under dc conditions, the overall figures of merit were measured and fitted to the physical models using genetic algorithms; by ac measurements, the capacitance and loss dependence on frequency were studied and equivalent circuit models were obtained. Capacitance – voltage behavior was also analyzed. The morphology of OPV active area film was investigated by Atomic Force Microscopy (AFM) in both tapping and current sensing methods. The OPVs exhibit efficiencies ranging from 1.2 to 3%, with fill-factors (FF) ranging from near 50% to near 70%. The relaxation frequencies can be correlated with the efficiency behavior, and with the micro electrical map obtained (and correlated with morphology) by AFM-current sensing. It was shown that how post-thermal annealing changes the micro electrical patterning and therefore, a suitable relationship with macroscopic behavior can be established.

The search for efficient materials for organic light emitting diodes is one of the most imperative research area. The focus is to obtain a bright large area emitter, limited by the low internal quantum efficiency of conventional organic emitters. Recently, a new generation of the organic materials (TADF) with a theoretical internal quantum efficiency up to 100%, opened new frameworks. However, significant challenges persist to achieve full understanding of the TADF mechanism and to improve the OLEDs stability. Starting from the photo-physical analysis, we show the relationship with the molecular electrical carrier dynamics and internal quantum efficiencies. The OLED structure, fabrication, and characterization are also discussed. Several examples for the full color emitters are given. Special emphasis on experimental results is made, showing the major milestones already achieved in this field.