Highly efficient, solution processed electrofluorescent small molecule white organic light-emitting diodes with a hybrid electron injection layer

Modelling the 3D Structure of PEDOT:PSS Supramolecular Assembly in Aqueous Dispersion Based on SAXS with Synchrotron Light

In this work, we study the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) structure in aqueous dispersion with small-angle X-ray scattering (SAXS). In-depth structure analysis is achieved based on a set of complementary and sophisticated algorithms, which provide not only shape and packing of chains but also 3D structure of the colloids. The structure information of the PEDOT chain was extracted from the well-known Guinier, Porod and pair distance distribution function (PDDF) analysis of the SAXS data, while the 3D modelling was achieved with the DAMMIF and DAMAVER programs in ATSAS software package. To the best of our knowledge, we first establish the 3D model of the PEDOT:PSS colloids’ structure that will help people to understand the supramolecular assembly in aqueous dispersion, which sheds light on the solution structure study of polymers that are widely used in daily life.

A Fluorescence-Phosphorescence-Phosphorescence Triple-Channel Emission Strategy for Full-Color Luminescence

Organic luminogens constitute promising prototypes for various optoelectronic applications. Since gaining distinct color emissions normally requires the alternation of the conjugated backbone, big issues remain in material synthetic cost and skeleton compatibility while pursuing full-color luminescence. Upon a facile one-step coupling, three simple but smart perchalcogenated (O, S, and Se) arenes are synthesized. They exhibit strong luminescent tricolor primaries (i.e., blue, green, and red, respectively) in the solid state with a superior quantum yield up to >40% (5-10 times higher than that in corresponding solutions). The properties originate from a fluorescence-phosphorescence-phosphorescence triple-channel emission effect, which is regulated by S and Se heavy atoms-dependent intersystem crossing upon molecular packing, as well as Se-Se atom interaction-caused energy splittings. Consequently, full-color luminescence, including a typical white-light luminescence with a Commission Internationale de I'Eclairage coordinate of (0.30, 0.35), is realized by complementarily incorporating these tricolor luminescent materials in the film. Moreover, mechanochromic luminescent color conversions are also observed to achieve the fine-tuning of the luminescent tints. This strategy can be smart to address full-color luminescence on the same molecular skeleton, showing better material compatibility as an alternative to the traditional multiple-luminophore engineering.

Enhanced electron transportation of PF-NR2 cathode interface by gold nanoparticles

In order to achieve a wider organic light-emitting diode (OLED) commercial popularity, solution processing inverted polymer light-emitting diode (iPLED) is a trend for further development, but there is still a gap for solution processing devices to achieve commercialization. The improvement of the performance iPLEDs is a research topic of intense current interest. The modification of the cathode interface layer of poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PF-NR₂) can greatly improve the performance of the devices. However, the electron transportation of the cathode interface layer of PF-NR₂ films is currently poor, and there is substantial interest in improving its electron transportation to further enhance the performance of organic optoelectronic devices. In this paper, gold nanoparticles (Au NPs) with a particle size of 20 nm were prepared and doped into the interface layer PF-NR₂ at a specified ratio. The electron transportation of the interface layer of PF-NR₂ was greatly improved, as judged by conductive atomic force microscopy measurements, which is due to the excellent conductivity of Au NPs. Herein, we demonstrate improved electron transportation of the interface layer by doping Au NPs in PF-NR₂ film, which provides important and practical theoretical guidance and technical support for the preparation of high performance organic optoelectronic devices.

Self-Assembled α-Cyanostilbenes for Advanced Functional Materials

In the specific context of condensed media, the significant and increasing recent interest in the α-cyanostilbene (CS) motif [ArCHC(CN)Ar] is relevant. These compounds have shown remarkable optical features in addition to interesting electrical properties, and hence they are recognized as very suitable and versatile options for the development of functional materials. This progress report is focused on current and future use of CS structures and molecular assemblies with the aim of exploring and developing for the next generations of functional materials. A critical selection of illustrative materials that contain the CS motif, including relevant subfamilies such as the dicyanodistyrylbenzene and 2,3,3-triphenylacrylonitrile shows how, driven by the self-assembly of CS blocks, a variety of properties, effects, and possibilities for practical applications can be offered to the scientific community, through different rational routes for the elaboration of advanced materials. A survey is provided on the research efforts directed toward promoting the self-assembly of the solid state (polycrystalline solids, thin films, and single crystals), liquid crystals, nanostructures, and gels with multistimuli responsiveness, and applications for sensors, organic light-emitting diodes, organic field effect transistors, organic lasers, solar cells, or bioimaging purposes.

Strategies to Achieve High-Performance White Organic Light-Emitting Diodes

As one of the most promising technologies for next-generation lighting and displays, white organic light-emitting diodes (WOLEDs) have received enormous worldwide interest due to their outstanding properties, including high efficiency, bright luminance, wide viewing angle, fast switching, lower power consumption, ultralight and ultrathin characteristics, and flexibility. In this invited review, the main parameters which are used to characterize the performance of WOLEDs are introduced. Subsequently, the state-of-the-art strategies to achieve high-performance WOLEDs in recent years are summarized. Specifically, the manipulation of charges and excitons distribution in the four types of WOLEDs (fluorescent WOLEDs, phosphorescent WOLEDs, thermally activated delayed fluorescent WOLEDs, and fluorescent/phosphorescent hybrid WOLEDs) are comprehensively highlighted. Moreover, doping-free WOLEDs are described. Finally, issues and ways to further enhance the performance of WOLEDs are briefly clarified.

An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes

Polymer light-emitting diodes (PLEDs) have attracted broad interest due to their solution-processable properties. It is well-known that to achieve better performance, organic light-emitting diodes require multilayer device structures. However, it is difficult to realize multilayer device structures by solution processing for PLEDs. Because most semiconducting polymers have similar solubility in common organic solvents, such as toluene, xylene, chloroform, and chlorobenzene, the deposition of multilayers can cause layers to mix together and damage each layer. Herein, a novel semiorthogonal solubility relationship was developed and demonstrated. For the first time, an alkane-soluble dendrimer is utilized as the electron-transport layer (ETL) in PLEDs via a solution-based process. With the dendrimer ETL, the external quantum efficiency increases more than threefold. This improvement in the device performance is attributed to better exciton confinement, improved exciton energy transfer, and better charge carrier balance. The semiorthogonal solubility provided by alkane offers another process dimension in PLEDs. By combining them with water/alcohol-soluble polyelectrolytes, more exquisite multilayer devices can be fabricated to achieve high device performance, and new device structures can be designed and realized.

Solution-processed transparent blue organic light-emitting diodes with graphene as the top cathode

Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

Intramolecular charge transfer interactions and molecular order of rod like mesogens

Photophysical studies, VT-XRD and¹³C solid state NMR investigation of three ring based dimethylamino mesogens reveal intramolecular charge transfer, smectic A_dmesophase and molecular order.

Deep blue organic light-emitting devices enabled by bipolar phenanthro[9,10-d]imidazole derivatives

Novel phenanthroimidazole derivatives with D–π–A structures have been successfully designed and prepared. Non-doped organic light emitting diodes (OLEDs) were fabricated by employing the compounds, which display deep blue emission.