This PDF file contains the front matter associated with SPIE Proceedings Volume 11473, including the Title Page, Copyright information, and Table of Contents.

Quantum dots (QD) change the display industry landscape as they are integrated into displays in various ways from color converters on LCD or OLED to electroluminescent QLED. Their unique optical and electronic properties such as the bandgap tunability, narrow emission bandwidth and high quantum yield enable us to make the display brighter and more efficient and colorful. After providing a brief overview of the current status of the display industry and technology trends, I will explain recent progress and future prospects of the QD display technology. Especially, I will discuss the technical challenges and development opportunities of inkjet-printed QLED displays.

Organic light emitting diodes (OLEDs) are thin, lightweight and flexible whilst still maintaining high efficiencies. Therefore, OLEDs are at the forefront of display technology and recently, applications of OLEDs have emerged in solid state lighting. Additionally, OLEDs can be made extremely flexible and stretchable, making them suitable for use in wearable electronics. Among light emitting materials for OLEDs, thermally activated delayed fluorescent (TADF) materials have shown great promise in the last few years. In this study, we report a solution processable TADF emitting polymer as an emissive material for OLEDs. The bespoke polymer structure has the TADF emitter 4-(9H-carbazol9-yl)-2-(3′-hydroxy-[1,1′- biphenyl]-3-yl)isoindoline-1,3-dione as a pendant group on a poly(methyl methacrylate) based polymer chain. We demonstrate ink-jet printed OLEDs using our TADF polymer, which allows for precise patterning without masks, deposition of nanometer scale thicknesses, and minimal wastage

Recently all-organic thermally activated delayed fluorescent (TADF) emitters have attracted great attention. In TADF emitters, nonemissive triplet states can be also harvested via population of emissive singlet states through reverse intersystem crossing (RISC). The RISC can be induced by the small energy gap between the lowest singlet (S1) and triplet (T1) states. Due to this ability of TADF, 100% internal quantum efficiency and high maximum external quantum efficiency (EQEmax) comparable to those of phosphorescent organic light emitting diodes (OLEDs) have been already reported in TADF OLEDs. In this study, we demonstrate high efficiency TADF OLEDs which are attributed to employing triazine acceptor type TADF compounds having high RISC rates(kRISC).

Reverse intersystem crossing (RISC) is the most crucial process in recently-developed thermally activated delayed fluorescence (TADF). Inclusion of locally excited triplet state(s) is considered to accelerate RISC. In this study, we show a systematic in silico design of TADF materials with very fast RISC. We also show our recent study on multiscale charge transport simulations based on the combination of quantum chemical calculations, molecular dynamics simulations, and kinetic Monte Carlo simulations.

I will summarize current work in my team to better understand and harness effects of molecular orientation, light extraction and thin film optics OLEDs. The orientation of emissive molecules strongly influences the efficiency of light extraction in OLEDs. However, finding links between chemical design and orientation remains an open challenge. This is in part because current measurement methods only determine an average orientation value but provide no information about the orientation distribution. We propose to overcome this limitation by a single-molecule imaging approach. This allowed us to obtain statistics of the orientation distribution in TADF host-guest systems.

Triplet exciton accumulation and singlet-triplet annihilation (STA) are major issues, which makes continuous-wave (CW) operation difficult, in organic lasers. We synthesized an organic laser dye, 2,6-dicyano-1,1-diphenyl-λ5σ4-phosphinine (DCNP), having a small singlet-triplet energy gap. In DCNP-doped 4-4΄-bis[(N-carbazole)styryl] biphenyl (BSBCz) films, the triplets formed on DCNP are easily transferred to BSBCz, resulting in the suppressed STA and triplet accumulation. With this system, we demonstrated true-CW laser operation, with a low threshold and high photostability. Laser emission was further characterized by plane-polarized light output, far-field beam interference, exciton decay lifetime, and visible beam observed on an illuminance paper.

We report strongly enhanced light outcoupling from phosphorescent OLEDs (PhOLEDs) fabricated on patterned polycarbonate (PC) and polyethylene terephthalate (PET) substrates. The patterns range from shallow (height h<200 nm) to deep (h~500 nm) convex PC patterns with period a ~750 vs ~400 nm, and concave PET/CAB (cellulose acetate butyrate) patterns with large m-size periods – a new promising approach. Bottom-emitting PhOLEDs on such substrates enhance the external quantum efficiency EQE ~2.4x to 2.8x vs devices on glass/ITO; the EQE of green and blue patterned PC/PEDOT:PSS OLEDs reached 56.5% and ~43%, respectively. The corrugated substrates (refractive index ~1.6) are fabricated by direct molding, amenable to R2R transfer, at room temperature. Surprisingly, OLEDs on substrates with narrower a and relatively low h show significant outcoupling enhancement despite h reduction across the OLED stack. OLEDS on substrates with a2 m (and large a/h) showed significant enhancement with fully

The external quantum efficiency of organic light emitting devices is affected by losses within the devices. We show that the seamless incorporation of 2-dimensional reflecting metagratings within the structure of organic light emitting devices can result in substantial changes and improvements in light emission characteristics. Quasiperiodic as well as periodic metagratings have been included. With periodic square lattice metagratings, enhancements in surface-normal emission intensity (of up to 4.8x) have been observed relative to a control device without a metagrating. The enhanced intensities in the normal direction is due to increased out-coupling of ordinarily waveguided light that is typically lost within the device. Electromagnetic simulations and measurements show that our metagratings greatly enhance the electromagnetic field intensity in the light emission layer, leading to increased emission normal to the plane of the layers.

A microcavity OLED, consisting of a conventional OLED stack with two metallic mirror electrodes, shows narrow-band emission centered around specific peak resonant wavelengths. These cavity modes are analogous to the energy states found in any resonator system, including musical instrument strings and 1-dimensional quantum square wells. Here we incorporate the microcavity OLED as a unit cell in a photonic crystal. Stacking N microcavities splits the resonant modes into N discrete states. We demonstrate methods to control the photonic density of states and to induce a photonic bandgap. Furthermore, we investigate the effect of various device variables, including N and the thickness of the semi-transparent metal electrodes, on emission properties such as peak wavelength, FWHM, and Q-factor for each of the photonic states. The experimental results are guided by a predictive computational modelling tool, which is critically important for the complex-architecture devices.

High-performance OLED microdisplays on CMOS backplanes have been developed using multi-stack white OLED architectures for higher brightness and longer lifetime – the expected benefits from stacked architectures. Unlike OLED lighting, which is bottom emission, the top-emitting OLED on the silicon backplane has a Fabry–Pérot parallel plate microcavity. The combination of the multi-stack approach and the cavity provides additional degrees of design freedom which can be used to optimize the interaction between the OLED formulation and optics of the device. This combination allows reduced power, balanced sub-pixel currents, and increased color gamut. Examples are shown of full color microdisplays made with 3, 4, and 5 stacks that are capable of 5,000 cd/m² peak luminance with an OLED power consumption for normal video of approximately 150-175mW per square cm of active area. We also show examples of low persistence displays operating at 10% duty cycles with peak luminance of 10,000 cd/m² and power consumption with normal video of less than 50 mW per square cm of active area. The broad toolkit demonstrated here enables the design optimization of multi-stack OLED microdisplays for many different product requirements spanning AR, VR and other near-eye applications.

Organic light emitting diodes (OLEDs) are promising candidates for the lighting revolution of the 21st century. Along with the ever-ongoing quest for stable emitter materials, strategies for improved out-coupling of light, cost- and energy efficient low temperature processing in particular ITO-free flexible transparent conductive electrodes need further attention to boost OLED technologies, because ITO fails to be mechanically stabile upon bending and the scarcity of indium translates into high and volatile prices. In this contribution we report on the design, realisation and characterization of a number of different low temperature processes for printed and spray coated TCE on flexible low cost substrates such as polyethylene terephthalate (PET), based on printed Ag and Cu nano-particle, particle-free and nano-wire inks. We will show that the attained highly ITO-free electrodes on PET show superior optical, electrical and mechanical performance as compared to PET/ITO samples.

The fabrication of silver nanowire electrodes (AgNWs) on elastomeric substrates using various patterning processes and embedding process allowed us to solve the problems of using conventional silver nanowire electrodes such as rough surface and complicated pattering process. When polymer light emitting diodes (PLEDs) were fabricated using the AgNWs electrode fabricated above, they showed stable light emission and much lower driving voltage than alternating current electroluminescence. As a result, a stretchable transparent electrode was fabricated to the extent that it can be used for low voltage driven patterned lightings.

Optogenetics is a technique to modulate neuronal activity in response to light. Here, we present two different light sources that can provide high spatial resolution for precise optogenetic stimulation of Drosophila melanogaster (fruit fly) larvae: organic light-emitting diodes (OLEDs) and smartphone displays. Using micro-structured OLED arrays, we stimulated sensory neurons in individual abdominal segments of Drosophila larvae and thus controlled their crawling direction. Furthermore, we developed a smartphone app that allows spectral, spatial, and temporal control over the light emitted by the display and used this to deliver fine patterns of light to constrain larval movement.

There is a significant correlation in organic semiconductor thin films between the morphology and electronic structure, and both have strong effects on device performance. In this presentation, we describe our investigations on the relationship of the morphology and corresponding electronic structure and electrical properties using scanning probe microscopy techniques, photoemission spectroscopy, and transport measurements on organic semiconductor thin films. We also present investigations on the effects on optoelectronic device performance especially after controlling the morphology by quasi-epitaxial growth on representative organic semiconductors.

OLEDs and other organic optoelectronic devices combine many attractive features. However, they are generally thought to be slow, limiting their range of possible applications. We demonstrate that by careful study of the factors limiting their bandwidth, and appropriate design in terms of device size, operating field and emitter lifetime exceptionally fast OLEDs can be made with modulation bandwidths up to 245 MHz, opening up new potential applications in communications, spectroscopy, sensing and ranging. In particular, we demonstrate visible light communication in which a single OLED transmits data at a rate exceeding 1 gigabit per second.

The high degree of order in organic single crystals often leads to optimum charge transport properties and their robustness under high current density which is attractive for solid state lighting and laser technology. However, conventional method of single crystal growth based on physical vapour transport is unsuitable for device integration and large area applications. Here, we present a vacuum processed approach to prepare organic single crystals on inch sized substrates and integrate them into organic light emitting devices (OLED). The device performance are characterized in comparison to standard OLED based on amorphous materials.

Electrically pumped emission of light-matter exciton-polaritons is of great fundamental and practical interest but so far suffers from poor efficiency. Here, we present a universal strategy to generate polariton emission from state-of-the-art organic light emitting diodes (OLED). We demonstrate green and red emitting devices reaching an external quantum efficiency above 12% and a luminance greater 10,000 cd/m^2 and providing narrowband (FWHM 16nm) and nearly angle-independent (shift <6nm) emission spectra. The device characteristics are readily tunable by changing coupling strength and cavity detuning. Our results show the practical relevance of strong coupling for providing spectrally pure and colour-stable electroluminescence.

We present a comprehensive model to analyze, quantitatively, and predict the process of degradation of OLEDs considering polaron, exciton, exciton–polaron interactions, exciton–exciton interactions and a newly proposed impurity effect. The loss of efficiency during degradation is presented as a function of quencher density. The density and generation mechanisms of quenchers are extracted using a voltage rise model. The comprehensive model is applied to stable blue phosphorescent OLEDs, and the results show that the model describes the voltage rise and external quantum efficiency loss very well, and that the quenchers in emitting layer are mainly generated by polaron-induced degradation of dopants. Quencher formation was confirmed from a mass spectrometry. The polaron density per dopant molecule is reduced by controlling the emitter doping ratio, resulting in the highest reported LT50 of 431 hours at an initial brightness of 500 cd/m2 with CIEy<0.25 and high EQE>18%.

The recent interest on the manipulation of chemical processes within confined electromagnetic environments has opened up new directions on theoretical efforts to rationally design and understand the emergent dynamics of organic molecules embedded in the former. In this work, we extent the theoretical methodology toolbox to treat these systems by presenting a variational approach applicable to different regimes of vibronic coupling (dynamical disorder) and light-matter couplings for organic molecules. We use this method to understand and predict the influence of coupling of molecular aggregates to photon fields on triplet harvesting. The latter, being a relevant photophysical process for the design of efficient optoelectronic devices, has been recently and experimentally shown to be effectively changed in optical microcavities.

Status of organic lasers, the challenges they face, and prospects for the future

We investigate the temperature dependence (from 16 K to 300 K) of an organic polariton laser, consisting of an amorphous organic semiconductor thin film in a planar microcavity. The polariton lasing threshold does not change between 45 K and room temperature, but increases when the temperature decreases below 45 K. This is accompanied by an energy relaxation bottleneck along the lower polariton branch at the lower temperature. This temperature dependence behavior is attributed to the competition between direct radiative pumping from exciton reservoir and phonon-induced relaxation at different temperature and explains the anomalously high thresholds in organic lasers.

Metal halide perovskites have emerged as promising gain media with the potential to realize wavelength-tunable, non-epitaxial laser diodes. This talk will focus on recent progress toward this goal, including continuous-wave optically-pumped lasing from methylammonium lead iodide (MAPbI3), the operation of MAPbI3 LEDs at ~kA/cm2 current densities, distributed feedback MAPbI3 LEDs that lase under optical pumping, and a new perovskite laser diode architecture that can be fabricated on silicon in a single, back-end solution processing step.

In organic LEDs, converting dark states (triplets) into bright states (singlets) has become a crucial procedure to develop high efficiencies. Essentially, the triplet-to-singlet conversion requires a mechanism to flip the spins of triplets towards realizing the triplet-to-singlet conversion. Our recent studies have shown that charge-transfer states present a vital mechanism to generate a spin-orbital coupling (SOC) to flip spins towards converting triplets into singlets in exciplex systems. Furthermore, organic-inorganic halide perovskites are known as strong-orbital materials formed with bright (J = 1, named as triplets) and dark (J = 0, named as singlets) states. Our studies found that the orbit-orbit interaction between light-emitting states plays an important role to convert the dark states into bright states in hybrid perovskites. This presentation will discuss the SOC effects on light emission in organic and perovskite materials in spontaneous and stimulated regimes.

In this work, we demonstrated that through the addition of large organic cation PEABr, the quality of cesium lead halide thin films has been enhanced by controlling the crystallization process and thus the domain size and morphology. As a result, by increasing the PEABr concentration to 40%, the perovskite thin films with a small domain size, highly oriented crystal structure and low defect density demonstrated a lowest amplified spontaneous emission threshold of 7 µJ/cm2. However, further increasing PEABr concentration will result in a slower energy transfer, which limits the population inversion process and thus showed a higher ASE threshold. Using this strategy, by tuning the halide ratio, the ASE emissions were observed over the broad visible range (from 490 nm to 680 nm), demonstrating its wide wavelength-tunability.

In this talk, I will present our recent efforts on the development of new materials and processing approaches to achieve efficient and stable perovskite light emitting diodes (LEDs) with tunable colors. First, surface passivation of metal halide perovskite nanocrystals will be discussed, which could not only reduce surface defects, but also protect the surface from the penetration of degradation agents (e.g. moisture). Second, a novel approach to achieve efficient blue emissions from hollow perovskite nanocrystals via quantum size effects will be introduced. Lastly, processing engineering to prepare metal halide perovskite thin films with desired morphological and electronic properties for LEDs will be discussed.

Metal halide perovskites are promising materials for next generation light emitting diodes, with external quantum efficiency (EQE) over 20% been demonstrated. However, the device stability and the EQE roll-off of perovskite light emitting diodes are currently far from satisfactory, and joule heating was claimed to be one of the main causes. In this work, by replacing the commonly reported TPBi electron injection layer, we significantly reduce the device driving voltage and thus heat generation. This leads to remarkably improved EQE roll-off and device stability. Moreover, while injection layers like TPBi often inhabit charge injection at cryogenic temperatures, the charge injection is barely affected in our new device stack, enabling us to understand the device behavior at such low temperatures and we can further mitigate the joule heating effects by cooling down the devices. Our new stack provides EQE of over 10% at 300 mA/cm2 and a record lifetime of T70 = 50 h at 100 mA/cm2 at RT.

Overcoming instability of metal halide perovskite emitters and their display applications

The preparation of wide-gap CsPbCl3 thin films from solution is impeded by the poor concomitant solubility of the precursor salts PbCl2 and CsCl. In the present study, we prepared superlattices of PbCl2 and CsCl by thermal evaporation. The superlattice shows an intense photoluminescence at 413 nm with a narrow line width of 10 nm (FWHM), which agrees with reports of CsPbCl3 single crystals. Most notably, the resulting layer structures support amplified spontaneous emission (ASE) in the deep blue spectral region at 427 nm (width 2.2 nm) under pulsed optical excitation (355 nm, 300 ps) above a threshold energy density of 190 μJ/cm² at room temperature (RT). This is the first report of CsPbCl3 thin films showing ASE at RT.

There is an urgent need to prepare environmentally friendly QDs that show high efficiency and better color purity for the consumer products. A strategy of tuning the wavelength and spectral width of the QDs is discussed to optimize the brightness and color space agreement. The critical parameters affecting photophysical properties, such as the uniformity of the InP QD core, the thickness and isotropic shape of the ZnSe shell, the electron/hole distribution, surface dangling defects, oxidative phase, and the stacking faults in the crystalline structure, should be carefully examined. It is also required to prepare more efficient and stable green and blue-emitting QDs by passivating interface defect structures and understanding of the degradation mechanisms in the devices.

Quantum dots (QDs) are a unique class of emitters with size-tunable emission wavelengths, saturated emission colors, near-unity luminance efficiency, inherent photo- and thermal- stability and excellent solution processability. In the past few years, efficiency and lifetime of quantum-dot light-emitting diodes (QLEDs) achieved tremendous progress. These encouraging facts foreshadow the commercialization of QLEDs, which promises an unprecedented generation of cost-effective, large-area, energy-saving, wide-color-gamut, ultra-thin and flexible displays. Here we review our activities associated with QLEDs, including exciton-generation mechanisms, material chemistry of charge-transporting layers and device engineering.

Here we show a novel EL device architecture: a durable/flexible textile-fiber-embedded PDMS+ZnS composite, driven by an in-plane electric field, which eliminated the requirement of highly transparent planar electrodes [1]. In our work, electrically conductive textile fibers were used as electrodes embedded in a PDMS+ZnS composite with parallel orientation. Using this system, we demonstrated various white colors-emitting ACEL devices by simple mixing of RGB EL phosphors with various weight ratios. We also found that the white light shows CIE coordinates of (0.338, 0.344) in 5:5 (blue:orange) mixing weight ratio condition, which is highly close to pure white color. We believe that such simple realization of RGB as well as various white lights suggest the easy applicability of in-plane electric field driven ACEL device in a wide range of colorful light-emitting systems.

A metallic microcavity OLED structure is shown to be an ideal building block for exploring 1D photonic crystals. By stacking N metallic microcavities we demonstrate the formation of photonic energy bands by splitting each single-cavity discrete mode into N hybridized resonance states. The splitting of the local cavity modes is found to directly mimic the formation of energy bands from Bloch and molecular orbital (MO) theory. The resulting energy band structure is manipulated by varying the thickness of the metallic mirrors and the cavities, including the formation of a photonic band gap by the introduction of a Peierls distortion to the 1D crystal. The metallic microcavity OLED structure enables direct observation of the interaction of individual cavity modes with the coupled microcavity superlattice due to the internal broadband emission sources. Recent experimental work confirms the transfer matrix simulations for simple structures and has laid the groundwork for future exploration.

In this work, we prepared chemical bonding polyimide (PI)-silica hybrid films as the light extraction layers for organic light-emitting diodes using 3-aminopropyltriethoxysilane (APTES) as coupling agent followed by sol-gel and thermal imidization process. Being benefited by the chemical bonding, homogeneous dispersion of silica was achieved to realized high optical transparent and low-hazed hybrid films. The hybrid films also exhibited high thermal stability with the Td (5 % weight loss temperature) of 507 oC. The hybrid films efficiently enhanced the efficiency of organic light-emitting diodes with maximum external quantum efficiency (EQE) of 23.5%, exhibiting an enhancement of 15% compared with the reference devices without the hybrid films.

High crystallinity of PEA2(Rb1-xCsx)2Pb3Br10 perovskite films are successfully fabricated in order to improve the surface coverage of perovskite film induced crystallization by low pressure flashing method in the spin-coating process. Due to this formation method for PEA2(Rb1-xCsx)2Pb3Br10 perovskite thin films, we were able to improve electroluminescence (EL) properties of hybrid perovskite blue light emitting device. The improved perovskite thin film can be achieved by one step spin-coating which can provide crystallization in vacuum environment under the concentration of solution-processed PEA2(Rb1-xCsx)2Pb3Br10 unchanged to promote the grain growth.The perovskite film produced by low pressure flashing method can improve the property and stability of devices.

We report imperceptibly micro-wrinkled organic light-emitting diodes (OLEDs) to define distortion-free pixel by in-situ deposition on two-dimensionally pre-stretched polydimethylsiloxane (PDMS) substrate. The developed fabrication process includes surface engineering for a low-temperature solution process. After releasing the pre-strain, a micro-wrinkled structure facilitates to maintain the clear shape of the pixel with the wrinkle period under 20 µm that is unrecognizable to the human eyes, whereas wrinkles of hundreds of µm are formed when using plastic films. The micro-wrinkled OLEDs show a luminance over 8,000 cd/m2, a maximum current efficiency of 7 cd/A and can endure two-dimensional 20% strain. Our in-situ fabrication method can become a new framework for stretchable OLEDs with simple and low-cost fabrication with improved visibility.

Organic-inorganic perovskite light-emitting devices have recently emerged as a reliable light source. Here, we developed a Single Layer Perovskite Light-Emitting Electrochemical Cells (SL-PeLEC) with laminated free-standing Carbon Nanotube Sheet (CNT) sheets as an effective charge electron injecting cathode electrode. The structure consists of bottom ITO-on-glass as a transparent electrode, the composite of CsPbBr₃:PEO:LiPF₆ with additive ionic salt as an emitting layer (EML) and 5 layers of CNT aerogel sheets as a top laminated cathode . Utilizing CNT free standing sheets laminated right on top of perovskite thin film in this simple single layer configuration has multiple benefits. Such CNT top cathode does not show any chemical degradation by reaction with halogens from perovskite, which is detrimental for metallic cathodes. Moreover, the formation of an internal p-i-n junction in perovskite EML composite layer by ionic migration under applied voltage bias and electric double layer (EDL) formation at each electrode interface is beneficially effecting CNT sheets by Li⁺ ionic doping and raises their Fermi level, further enhancing electron injection. Besides, inspired by successes of ionic additives in LECs and electrochemical doping of perovskite with alkali metals, we leveraged a lithium salt, LiPF₆, within a CsPbBr₃:PEO composite matrix to achieve optimal ionic redistribution and doping effects in this SL-PeLEC. Although initially CNT electrode has slightly high sheet resistance, the SL-PeLEC device has a low turn-on voltage of 2.6v and a maximum luminance intensity of 530 cd/m², confirming the n-doping increased conductivity. This work provides a unique route toward flexible and bright perovskite LECs with stable and transparent CNT electrodes that can have injection efficiency tuned by poling induced ionic EDL-doping.

Three blue fluorescent materials were newly synthesized by attaching triphenylamine side groups at their ortho, meta, and para positions to a dual core moiety of anthracene and pyrene, two chromophores with good luminous efficiency; these three materials were 2-(6-(10-(2-(diphenylamino)phenyl)anthracen-9-yl)-pyren-1-yl)-N,N-diphenylaniline (o-TPA-AP-TPA), 3-(6-(10-(3-(diphenylamino)phenyl)anthracen-9-yl)pyren-1-yl)-N,N-diphenylaniline (m-TPA-AP-TPA), and 4-(6-(10-(4-(diphenylamino)phenyl)anthracen-9-yl)pyren-1-yl)-N,N-diphenylaniline (p-TPA-AP-TPA), respectively. The optical, thermal, and electroluminescence (EL) properties of the synthesized materials were measured. All three materials were found to be real blue emitters in the solution state and display high PLQY values. A device doped with p-TPA-AP-TPA displayed a very high efficiency of 9.14 cd A-1 and an EQE of 8.38% at a high luminance of 5000 cd m-2

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.

Cavity top emission organic light-emitting diodes (TOLEDs) suffer from an angular color shift due to the microcavity effect, called white angular dependence (WAD). The hazy films embedding air-gaps exhibit high transparency as well as enhanced scratch resistance. The haze was systemically controlled by changing the size of the air-gaps, determined by the size of the nanostructure and the viscosity of the coated resin. The optimized hazy film significantly reduced WAD about 92 % in a multi-color TOLED without complicated design for red, green and blue colors. Optical simulations using FDTD were conducted to interpret the effect of haze on WAD.