This PDF file contains the front matter associated with SPIE Proceedings Volume 10362, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Organic semiconductors have attracted interest for electronic applications due to their potential for use in low-cost, large-area, flexible electronic devices. In this talk I will discuss the development of metallocenes-based dimers as n-dopants for use in semiconductors, 2D materials and electrodes, and their resulting impact on material properties and device performance. In particular I will focus on the application of photo-induced doping of low electron affinity compounds using air-stable organometallic compounds. The mechanism of doping and the application of the doping for fabrication of organic light emitting diodes (OLEDs) will be discussed. I will also briefly discuss recent work on the development of materials that have small excited state singlet-triplet energy gaps, which may be of interest as hosts or emitters for OLED applications.

The process of triplet harvesting is by thermally activated delayed fluorescence, ‘TADF’, i.e. E-type delayed fluorescence, is now well established. In this talk I shall discuss how this triplet harvesting mechanism is affected by molecular architecture. Detailed photophysical measurements of intramolecular charge transfer (ICT) states have been made both in solution and solid state. Temperature dependent time resolved emission, delayed emission and photoinduced absorption are used to map the energy levels involved in molecule decay, and through detailed quantum chemical modelling, true electron exchange energies and other energy barriers of the systems are determined with the real states involved in the reversed intersystem crossing mechanism elucidated. Using the vibronic coupling second order spin orbit interaction we go on to show how both D-A-D molecule structure and conformation control TADF and efficiency in a TADF OLED. By confirming the vibronic coupling mechanism of rISC (and ISC) we can now start to think about true molecular design for TADF emitters. 1. Etherington, M. K., Gibson, J., Higginbotham, H. F., Penfold, T. J. & Monkman, A. P. Revealing the spin-vibronic coupling mechanism of thermally activated delayed fluorescence. Nat Commun 7, 13680 (2016). 2. Gibson, J., Monkman, A. P. & Penfold, T. J. The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules. ChemPhysChem 1–7 (2016). doi:10.1002/cphc.201600662 3. Dias, F. B. et al. The Role of Local Triplet Excited States in Thermally-Activated Delayed Fluorescence: Photophysics and Devices. Adv. Sci. 3, 1600080 (2016).

We demonstrate enhanced photoluminescence (PL) from an optically pumped bias driven molecular tunneling junction (Au-substrate/self assembled molecular monolayer/Au-tip) with molecules chemically bound to the Au substrate. The gap between a sharp gold tip and a flat gold substrate covered with a self-assembled monolayer (SAM) of 5-chloro-2 mercaptobenzothiazole (Cl-MBT) molecules can be used as an extremely small optical gain medium. When a bias-voltage is applied between tip and sample such that electrons tunnel from the Cl-MBT’s highest occupied molecular orbital (HOMO) to the tip, holes are left behind in the molecules. These can be repopulated by hot electrons that are created by the laser-driven plasmon oscillation on the metal surfaces enclosing the molecule. Emission of photons occurs from the recombination of plasmon excited hot electrons with holes in the HOMO of surface bound molecules below the tip. Varying the laser pump power or alternatively the applied bias voltage shows in both cases a distinct threshold above which enhancement of the optical signal occurs. Solving the rate equations for this system shows that optical feed-back by the gap mode’s near field can efficiently stimulate the emission process. The system reflects many essential features of a superluminescent organic light emitting diode.

Thermally activated delayed fluorescence (TADF) is an upcoming key technology for organic light-emitting diodes (OLEDs). For the first time, OLED materials that combine efficiency, stability and a deep blue color point are available. In this work, we introduce the TADF technology and give a status update and development roadmap towards commercialization. As a highlight, we will especially feature a status update for deep-blue emitters with high stability and good color point, which are useful for efficient OLED displays.

This presentation reports our recent studies on the understanding of spin-dependent processes in TADF (Thermally Activated Delayed Fluorescence) light-emitting materials based on magneto-optical studies. Recently, we have performed magneto-optical studies on TADF light-emitting molecules (DMAC-TRZ) by using magneto-photoluminescence (magneto-PL). Our magneto-PL studies provide the first evidence that the TADF is a spin-dependent process occurring in charge-transfer states. Essentially, the key spin-dependent process, namely spin mixing, necessarily required to activate the TADF, is determined by the competition between two critical parameters: (i) exchange interaction which functions as a resistance force to the TADF and (ii) spin-orbital coupling which acts as a driving force to the TADF. Therefore, controlling the exchange interaction and spin-orbital coupling becomes a critical issue in the development of highly efficient TADF light-emitting materials. By using magneto-PL studies, we further found that, doping soluble magnetic nanoparticles (surface-modified Fe3O4) can conveniently change the exchange interaction and spin-orbital coupling, and consequently alters the TADF rate. At low doping concentrations, the spin-orbital coupling is enhanced, leading to an increase on TADF rate. However, at high doping concentrations, the exchange interaction is increased, causing a decrease on the TADF rate. Furthermore, we studied the polarization effects of spin mixing in liquid TADF materials by using various solvents with different polarities. We observed that increasing the host polarization can directly weaken the spin mixing and leads to a decrease on the TADF rate. This experimental observation indicates that host polarization can weaken the spin-orbital coupling and thus decreases the driving force to TADF. Clearly, the magneto-PL studies provide an insightful understanding on the spin-dependent process to control the TADF rate in organic light-emitting materials.

Extracting the “internally waveguided” light from OLEDs, which together with losses to plasmons at the metal cathode typically account for > 50% of the light generated in the emission zone, has proven to be a particularly challenging problem. To address this problem, we fabricated devices on nano-patterned plastic substrates that disrupt the internal waveguiding. We describe thermally evaporated small molecule fluorescent and phosphorescent OLEDs fabricated on corrugated polycarbonate (PC) and polyethylene terephthalate (PET) substrates nanopatterned in a roll-to-roll process. We compare the devices fabricated on plastic/ITO to those on plastic/PEDOT:PSS and the effect of adding a µm-scale Cu honeycomb mesh to the integrated substrate/anode as well. Depending on the height and pitch of the pattern, up to a 2.5 fold increase in the outcoupling factor is observed relative to the flat substrate. Issues related to the fidelity of the conformal deposition of the various layers on the patterned plastic are also discussed, particularly the effect of the nanopatterns on device stability.

Molecular orientations and energy levels at organic interfaces are critical knowledge in guiding materials selections in organic electronic device design. The correlation between molecular orientations and the energy levels when two different molecules are placed in contact with each other is discussed. Several combinations of different organic semiconducting molecules are investigated here with a broad range of structures. In-situ ultraviolet photoemission spectroscopy (UPS) is used to directly probe the energy levels at the molecular interfaces.

While the internal quantum efficiency of an OLED can reach 100%, its external quantum efficiency (EQE) is limited to 30% because of light trapped in waveguided mode, SPP mode and substrate mode. In this study, we achieve more than 2X enhancement in EQE by using a corrugated substrate and a hemispherical lens. Polarized angle-resolved electroluminescence spectroscopy is used to analyzed the EL data, and the results are compared with optical simulation. We find the efficiency enhancement mainly comes from the diffraction of the SPP mode towards air mode due to the corrugated substrate, and the hemispherical lens assists the light extraction by extending the air cone into the substrate mode.

Since its first demonstration in 1998, electrophosphorescence has yielded 100% internal quantum efficiency OLEDs (PHOLEDs) across the color gamut. This advance has given birth to a huge global OLED display industry, now estimated to be >$15B, or more than 10% of all displays made. While red and green devices have shown extraordinary operational lifetimes, blue PHOLEDs have had unacceptably short lifetimes. In this talk I discuss the fundamental origins of this deficiency1, and approaches to extending the lifetime of blue PHOLEDs. Indeed, recent results in our laboratory have already yielded a 10 fold improvement in lifetime, the first such major improvement in almost a decade2. The understanding gained from these experiments suggest that much longer lifetimes, even for very deep blue emitting PHOLEDs, is possible. In particular, I will discuss the use of hot excited state managers as a means to greatly extend the lifetime of blues for both displays and lighting. 1. N. C. Giebink, B. W. D’Andrade, M. S. Weaver, P. B. Mackenzie, J. J. Brown, M. E. Thompson and S. R. Forrest, J. Appl. Phys. 103, 044509 (2008). 2. Y. Zhang, J. Lee and S. R. Forrest, Nature Commun. 5, 5008 (2014).

OLEDs are key devices for realizing next-generation displays such as flexible displays. Although the emission mechanism along with new luminescence materials have been intensively studied with the goal of harvesting all excitons as emission, it has not been uncommon to hear of devices with internal quantum efficiencies of approximately 100% that use phosphorescent or thermally activated delayed fluorescent (TADF) emitters in recent years. Thus, the device performances directly related to practical applications, such as operational lifetime and color purity, have begun to attract much attention. Here, we report on recent advances in phosphorescent OLEDs (PHOLEDs) related to these two device performances. First, the molecular design of the host material to obtain an operationally stable PHOLED is clarified. By analysing the device characteristics of several PHOLEDs utilising similar TADF materials as hosts, a TADF material with a small molecular size is found to be suitable for the phosphorescent host. Second, we demonstrated efficient green OLEDs with high color purity utilising a platinum complex with a rigid molecular structure. A current efficiency of 84 cd/A was obtained from a bottom-emitting OLED with CIE x-y coordinates of (0.27, 0.67), which is much greater than that of a bottom-emitting green OLED using conventional iridium complexes with CIE x-y coordinates of (0.33, 0.62). Furthermore, the CIE x-y coordinates reached (0.18, 0.74) upon employing a top-emitting structure.

Organic light-emitting diodes (OLEDs) are being increasingly applicable in flat-panel displays, such as television and mobile phone, and have a great potential to become the next generation solid-state lighting sources. One of the most attractive strategies is to construct OLEDs with low cost purely organic materials, where high cost phosphorescent materials containing rare or noble metals are not involved in the device fabrication. We have proposed a simple strategy towards high-performance fluorescent OLEDs. The designed devices are merely composed of stacked p-type hole-transport layer and n-type electron-transport layer, resulting in a planar pn heterojunction configuration similar to their inorganic counterparts, namely light emitting diodes (LEDs). In this novel device, the excitons are generated and decay at the pn junction interface due to the synergetic interaction of p-type and n-type materials, finally giving the light emission. In addition, a novel strategy towards simultaneously low-driving voltage and high efficiency fluorescent OLEDs was also proposed using an active planar pn heterojunction as the exciton generation region and conventional fluorescent dye or thermally activated delayed fluorescence (TADF) material as the emitter. The current findings highlight the significance of the role of the organic active planar pn heterojunction in fabrication of high-performance and structure-simplified OLEDs with conventional fluorescent and TADF emitters, and also enlighten that organic active pn heterojunction should play a much more important role in electric-to-light conversion devices as it has done in the light-to-electric photovoltaic devices.

Although the promise of realizing lower cost fabrication by means of solution-based processing techniques, such as spin coating, web coating or inkjet printing, has been one key driver behind the interest in OLEDs for the last two decades, the lower stability of devices made by these techniques has been a long standing issue. With recent advances in developing solution-processable small molecule materials, it is now possible to make OLEDs of the same small molecule materials by either solution coating or vacuum deposition. Despite this, there continues to be an intriguing stability gap. In this work, we investigate this phenomenon with the purpose of identifying its root causes. Electroluminescence, delayed electroluminescence and photoluminescence measurements are used to study and compare between the aging behavior in OLEDs made by spin-coating versus vacuum-deposition. Hole-only devices are also utilized, and employed to study the effects of charges and excitons, separately and combined. The results reveal that the faster degradation of solution-processed devices relative to their vacuum-deposited counterparts under electrical stress is due to a faster molecular aggregation process. Excitons and interactions between them and polarons appear to play a leading role in inducing this phenomenon. Results from these investigations will be presented and discussed.

Multilayered small-molecule organic light-emitting diodes (OLEDs) have been commonly used for balanced charge transport and exciton confinement. However, standard method that uses high-vacuum deposition for multilayered OLEDs entails high material and fabrication cost, and it has been a critical impediment to low-cost production. Solution-processing of small-molecule OLEDs has been considered as a promising method, but limited luminous efficiency of solution-processed OLEDs have also been a hurdle for practical use. Therefore, high-efficiency in solution-processed small-molecule OLEDs with a simple device structure should be developed. Here, we report highly efficient solution-processed simplified OLEDs using novel electron-transporting host materials based on tetraphenylsilane with pyridine moieties. These host materials have high triplet energy levels (> 2.8 eV), wide band gaps (> 4.0 eV), and high glass transition temperature. We additionally used multifunctional polymeric hole injection layer and mixed-host emitting layer to achieve simple device architecture without hole transporting or electron blocking layer. Our novel electron transporting host materials which have higher electron transporting ability and triplet energy levels than that of conventional electron transporting host material (2,2′,2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) provided more balanced charge transport and efficient energy transfer preventing backward energy transfer from phosphorescent dopants to host. Orange-red (~97.5 cd/A), green (~101.5 cd/A), and white (~74.2 cd/A) solution-processed phosphorescent OLEDs with simple device structure showed the highest recorded electroluminescent efficiencies of solution-processed OLEDs without additional light outcoupling structure reported to date. We also demonstrated a solution-processed flexible solid-state-lighting device as a potential application.

Charge transport is one of the most important factors for various devices. However, for organic devices, such as organic light-emitting diodes, charges are transported in amorphous molecular aggregates, and the prediction and detailed analysis has been difficult so far. Here, we show our recent study on multiscale charge transport calculations based on our preceding works[1,2]; the combination of quantum chemical calculations, molecular dynamics simulations, and kinetic Monte Carlo simulations. The calculations are performed by explicitly considering organic molecules, which allows detailed molecular level analysis. [1] Suzuki, F., Shizu, K., Kawaguchi, H., Furukawa, S., Sato, T., Tanaka, K. & Kaji, H., J. Mater. Chem. C 3, 5549 (2015). [2] Uratani, H., Kubo, S., Shizu, K., Suzuki, F., Fukushima, T. & Kaji, H., Sci. Rep. 6, 39128 (2016).

Organic-inorganic perovskites have revolutionized the optoelectronics field, providing materials with a wide range of properties for solving numerous applications. Indeed, much recent work has been focused on nanostructured perovskites, with quantum dots, nanowires, and nanoplatelets showing tremendous potential. Here, we utilize the unique tunability of 2D perovskite nanoplatelets to build LEDs that span the visible spectrum. Quantum confinement in the z direction drives a significant blueshift, allowing for blue devices utilizing the bromide system and orange devices utilizing the iodide system. We demonstrate that excess ligand addition is crucial to achieving this blueshift in thin films that otherwise suffer from energy funneling. We build devices that show electroluminescence from 440 nm to 650 nm, although they still suffer from low efficiencies due to low photoluminescence quantum yields. We finally demonstrate that these materials suffer from reversible degradation with an applied electric field, further limiting the efficiency. The favorable optoelectronic properties of perovskite materials, combined with the blueshift due to quantum confinement, shows the promise of these materials as a new class of low cost emitters.

Organometal halide perovskite light-emitting diodes (LEDs) with laminated carbon nanotube (CNT) electrodes are reported. The LEDs have an indium tin oxide (ITO) bottom electrode, a screen printed methylammonium lead tribromide (MAPbBr₃)/polymer composite thin film as the emissive layer, and laminated CNT as the top electrode. The devices can be turned on at 2.2 V, reaching a brightness of 4,960 cd m⁻² and a current efficiency of 1.54 cd A⁻¹ at 6.9 V. The greatly simplified fabrication process in this work can potentially lead to the scalable manufacturing of large size and low cost LED panels in the future.

Emitting dipole orientation (EDO) is an important issue of emitting materials in organic light-emitting diodes for an increase of outcoupling efficiency of light. The origin of preferred orientation of emitting dipole of iridium-based heteroleptic phosphorescent dyes doped in organic layers is revealed by simulation of vacuum deposition using molecular dynamics along with quantum mechanical characterization of the phosphors. Consideration of both the electronic transitions in a molecular frame and the orientation of the molecules at the vacuum/molecular film interface allows quantitative analyses of the EDO depending on host molecules and dopant structures. Interactions between the phosphor and nearest host molecules on the surface, minimizing the non-bonded van der Waals and electrostatic interaction energies determines the molecular alignment during the vacuum deposition. Parallel alignment of the main cyclometalating ligands in the molecular complex due to host interactions rather than the ancillary ligand orienting to vacuumleads to the horizontal EDO.

Comparing rigid inorganic layer, polymeric semiconducting gate layer exhibits superior flexibility as well as efficient carrier manipulation in high frequency AC cycles. Mechanism of the carrier manipulation at the gate in forward and reversed bias of AC cycle is studied. The flexible PET-based AC-OEL device with poly[(9,9-bis(3'-((N,N-dimethyl)-Nethylammonium)- propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-Br) gate shows a stable electroluminescent performance in frequency sweep with a color rendering index (CRI) over 81 at 2800K color temperature.

Field induced electroluminescence of either organic or inorganic fluorescent materials under alternating current (AC) has been of great attention as a potential candidate for next generation displays, lightings and sensors. Unique device architecture in which an emitting layer is separated with an insulator from electrode offers a new platform for designing and developing a variety of types of ELs. Here, we demonstrate high-performance field-induced AC polymer electroluminescence (AC-PEL) devices with high brightness, high efficiency and color-tunability. We also present a non-volatile EL memory in which arbitrarily chosen EL states are programmed and erased repetitively with long EL retention. Our memory is based on utilizing the built-in electric field arising from the remanent polarization of a ferroelectric polymer which in turn controls the carrier injection of an AC-PEL device. The device exhibits two distinctive non-volatile EL intensities at constant reading AC voltage, depending upon the programmed direct current (DC) voltage on the ferroelectric layer. DC programmed and AC read EL memories are also realized with different EL colors of R, G and B. Finally, we show that simultaneous sensing and visualization of the conductive substance is achieved when the conductive object is coupled with the light emissive material layer on our novel parallel-type AC-PEL device. A variety of conductive materials can be detected regardless of their work functions, and thus information written by a conductive pen is clearly visualized, as is a human fingerprint with natural conductivity.

An ohmic electrical contact is one that allows the largest possible current density limited by space-charge effects to be injected into the adjoining semiconductor. This is key to maximizing device efficiency and reliability, and thus fundamental to all semiconductor devices. A long-standing challenge for organic (and other solution-based) electronics is the lack of a general solution-based compatible strategy to fabricate ohmic contacts at will. To overcome these challenges, we have recently developed self-compensated heavily-doped polymers with ultrahigh and ultralow workfunctions, and polyelectrolyte interlayers for 2D interface doping. Unprecedented p- and n-doped conductive polymer films over an ultrawide work function range of 3.0 eV to 5.8 eV have been obtained, enabling solution-processed ohmic contacts for light-emitting diodes, solar cells, photodiodes and transistors. Self-aligned doped contacts have also become possible. We anticipate that these strategies will enable ohmic contacts to also be made to other advanced semiconductors, including quantum dots, nanotubes and 2D materials, and open up new and technologically interesting device architectures for various photonic and non-photonic applications. Using these materials, we have developed new understanding of the physics of work function and ohmic contacts relating to doped organic semiconductors. The localization of charge carriers in organic semiconductors, different from conventional band semiconductors, leads to important differences in the essential physics.

The printed electronics industry offers a paradigm change in manufacturing, cost and environmental impact when compared to the conventional semiconductor industry. Printed electronic devices are expected to be mass-produced from less-energy-demanding processes over large areas and on flexible substrates with techniques that closely resemble the well-known mass production of printed media on paper. Organic light-emitting diodes (OLEDs) offer great versatility in the design of application-specific light sources; yet examples of OLEDs fabricated on exotic substrates that differ from glass and plastic are still scarce. In this talk we will present recent examples of OLEDs fabricated on unconventional substrates, including nanocellulose and shape memory polymers.

The use of metal halide perovskites for optoelectronic devices beyond solar cells is gaining growing attention. Perovskites with different compositions are promising as tuneable light emitters for the whole visible spectral region [1]. We report solution processed perovskite laser devices that show amplified spontaneous emission and lasing. We have fabricated surface emitting perovskite distributed feedback lasers by spin-coating CH3NH3PbI3 precursor solutions in ambient atmosphere on nanoimprinted grating substrates [2]. These lasers exhibit narrow lasing linewidths below 0.2 nm and an excellent stability of more than 5×10^7 pulses at 1 kHz repetition rate. Lasing at different wavelengths could be achieved on a single substrate by integrating different grating periods on the same substrate. While the emission wavelength of CH3NH3PbI3 is in the deep red to infrared spectral region, the lasing emission can be shifted into the visible by a gradual exchange of iodine to bromine. By adapting the grating period to the emission spectra of the mixed halide perovskite, we achieved lasing in the visible. Furthermore, we demonstrate high-quality perovskites fabricated by ink-jet printing on flexible substrates. Such films show strong amplified spontaneous emission with a clear ASE intensity threshold. References [1] B. R. Sutherland and E. H. Sargent, "Perovskite photonic sources," Nat. Photonics 10, 295–302 (2016). [2] P. Brenner, M. Stulz, D. Kapp, T. Abzieher, U. W. Paetzold, A. Quintilla, I. A. Howard, H. Kalt, and U. Lemmer, "Highly stable solution processed metal-halide perovskite lasers on nanoimprinted distributed feedback structures," Appl. Phys. Lett. 109, 141106 (2016).

During the last two decades, organic semiconductor lasers (OSLs) have been attracted much attention due to their advantageous properties such as wavelength tunability in visible range [1], low cost, flexibility and large area fabrication [2]. These properties make them good candidates for a range of applications including sensing, spectroscopy and optical communication. However, only optically pumped organic lasers have been realized so far and the demonstration of an electrically-driven organic laser diode still remains a very challenging task. To achieve electrically pumped OSLs, much effort has been focused on the reduction of the energy threshold of optically pumped organic lasers by enhancing the gain media properties and optimizing the resonant cavities. The injection of high current density involves Joule heating which causes degradation and breakdown of the device. Moreover, the presence of high charge density induces multiple annihilation processes such as exciton-polaron quenching, polaron absorption and electric field dissociation which are ones of the causes of device external quantum efficiency rolloff. A fundamental understanding of the physical mechanisms governing the device operation is crucial to optimize the device performance and overcome the limitation processes to the achievement of an electrically driven OSLs. Electrical simulation of an organic light emitting diode under high current density is performed in order to predict the current at high voltage. The influence of the various annihilation processes is investigated by solving the exciton continuity equation. 1. O. Mhibik et al., Appl. Phys. Lett. 102, 41112 (2013). 2. C. Ge et al., Opt. Exp. 18, 12980–12991 (2010).

Electroluminescence in organic light-emitting diodes is simulated by the master equations for free carriers and excitons. The IV characteristics of both unipolar and bipolar devices can be well reproduced. The luminous efficacies of the phosphorescent OLEDs, which are doped with Ir(ppy)₃ in the emission layer, depend on both the triplet generation zone and the triplet transfer capability. Triplet diffusion into the hole-transport layer is primarily attributed to the decline in efficiencies of OLEDs with low emitter concentrations. Higher luminous efficacies can be obtained by graded doping profiles with the merits of broad triplet distribution within and confined to the emission layer. Moreover, triplet-polaron quenching plays a more significant role in the triplet loss than triplet-triplet annihilation does according to our simulations.

Reliability remains an ongoing challenge for organic light emitting diodes (OLEDs) as they expand in the marketplace. The ability to withstand operation and storage at elevated temperature is particularly important in this context, not only because of the inverse dependence of OLED lifetime on temperature, but also because high thermal stability is fundamentally important for high power/brightness operation as well as applications such as automotive lighting, where interior car temperatures often exceed the ambient by 50 °C or more. Here, we present a strategy to significantly increase the thermal stability of small molecule OLEDs by co-depositing an amorphous fluoropolymer, Teflon AF, to prevent catastrophic failure at elevated temperatures. Using this approach, we demonstrate that the thermal breakdown limit of common hole transport materials can be increased from typical temperatures of ∼100 °C to more than 200 °C while simultaneously improving their electrical transport properties. Similar thermal stability enhancements are demonstrated in simple bilayer OLEDs. These results point toward a general approach to engineer morphologically-stable organic electronic devices that are capable of operating or being stored in extreme thermal environments.

Dramatic improvements in white organic light emitting diode (OLED) performance and lifetime over the past decade are driving commercialization of this technology for solid-state lighting applications. As white OLEDs attempt to gain a foothold in the market, however, the biggest challenge outside of lowering their manufacturing cost arguably now lies in creating an architecturally adaptable form factor that will drive public adoption and differentiate OLED lighting from established LED products. Here, we present concepts based on kirigami (the Japanese art of paper cutting and folding) that enable intricate three-dimensional (3D) OLED lighting structures from two dimensional layouts. Using an ultraflexible, encapsulated OLED device architecture on 25 ~ 60 μm thick clear polyimide film substrate with simple cut and fold patterns, we demonstrate a series of different lighting concepts ranging from a simple ‘pop up’ structure to more complex designs such as stretchable window blind-like panel, candle flame, and multi-element globe lamp. We only find slight degradation in OLED electrical performance when these designs are shaped into 3D. Our results point to an alternate paradigm for OLED lighting that moves beyond traditional 2D panels toward 3D designs that deliver unique and creative new opportunities for lighting.

The distinguishable and non-distinguishable 6-bit (64) grayscales of green and red organic light-emitting diode (OLED) were experimentally investigated by using high-sensitive photometric instrument. The feasibility of combining external detection system for quality engineering to compensate the grayscale loss based on preset grayscale tables was also investigated by SPICE simulation. The degradation loss of OLED deeply affects image quality as grayscales become inaccurate. The distinguishable grayscales are indicated as those brightness differences and corresponding current increments are differentiable by instrument. The grayscales of OLED in 8-bit (256) or higher may become nondistinguishable as current or voltage increments are in the same order of noise level in circuitry. The distinguishable grayscale tables for individual red, green, blue, and white colors can be experimentally established as preset reference for quality engineering (QE) in which the degradation loss is compensated by corresponding grayscale numbers shown in preset table. The degradation loss of each OLED colors is quantifiable by comparing voltage increments to those in preset grayscale table if precise voltage increments are detectable during operation. The QE of AMOLED can be accomplished by applying updated grayscale tables. Our preliminary simulation result revealed that it is feasible to quantify degradation loss in terms of grayscale numbers by using external detector circuitry.

Three materials had highly twisted molecular structures. In film state, excimer emission can be interpreted as result of orientation effect. Wavelength of excimer was controlled through the change of center position of triple core chromophore, and the CIE of white light could be controlled.

A novel orange-red phosphorescent iridium complex PR-24 has been successfully synthesized and characterized. By using this material, we demonstrated the high-efficiency OLED devices. The best efficiency was achieved for a device using PR-24 as the dopant, exhibiting 25.8 cd/A current efficiency, 20.0 lm/W power efficiency and 15.9% EQE at 1000 cd/m2 . Moreover, when using the optimized co-host configuration, PR-24 shows a remarkable lifetime T₅₀ of 211,000 h for an initial luminance of 1000 nits .

High refractive index polymer-based scattering layers used as internal light extraction layers are a promising low-cost approach to enhance the luminous efficacy of organic light-emitting diodes (OLEDs). In order to avoid damaging of the OLED layers a structured and contactless deposition method for the polymer-based scattering layers is required. For enhanced lifetime of the devices the water diffusion through the scattering layer has to be eliminated by a structured patterning technique. Inkjet printing offers both a contactless and structured deposition. In this study we evaluate inkjet printing of nanocomposite polymer-based scattering layers for OLEDs. A detailed view on the material and process development is given. This involves an optimization of ink formulation, printing parameters as well as layer formation. The resulting haze values of the scattering layers at 550 nm vary between 40% and 90% for different layer thicknesses. The gain in external quantum efficacy of top-emitting OLEDs induced by light scattering compared to reference devices peaks at a factor of 2.3. The obtained results are discussed and verified by an optical volume scattering simulation model which will be presented in full detail. Also a parameter variation study and its impact on extraction efficiency will be shown.

The light out-coupling efficiency of top-emitting OLED devices with different micro-structures was investigated with the aid of software FDTD solutions. The micro-structures included surface grating, wavy shape and spherical micro lens respectively. The simulation results indicated that the micro-structure was helpful to improve the light out-coupling efficient of OLED. Further more a complex spherical crown surface micro-structure was designed. The light out-coupling efficient of top-emitting OLED with the complex spherical surface improved 14% compared that of the device with smooth surface and 6% compared with micro lens.

This work reports the photophysical properties of copper (I) complexes and CdTe QDs loaded in a mesoporous silica matrix obtained by sol-gel method with an average pore diameter of 10 nm. The colloidal suspension of CdTe, synthesized in aqueous phase, presents maximum emission at λ_em = 520 nm with full width at half maximum (FWHM) of 45 nm. While loaded into the solid SiO₂ matrix, the QD emission had small shift, according to the type of incorporation strategy. The complexes Cu₄I₄py₄ (1) and C₃₀H₂₈N₂O₂PCuI (2) incorporated on mesoporous silica showed a shift in emission of λ_em = 580 nm to 645 nm and λ_em = 660 nm to 575 nm, respectively. This shift of the emission is caused by distortion of the molecular complex, in the MLCT excited state, inside the matrix, known as rigidochromic effect. Also, a sensitivity of these hybrids materials (1@SiO₂ and 2@SiO₂) was observed to oxygen. The mesoporous matrix dispersed the molecules of the complex, so as to enable a reversible interaction with oxygen in the center of the metal that quenches of luminescence and provides a new functionality to the complex. The new functional materials proposed in this study have potential for applications in optical materials devices.