A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented. The structure−property−performance relationships of many classes of ETMs, both small-molecule- and polymer-based, that have been widely used to improve OLED performance through control of charge injection, transport, and recombination are highlighted. The molecular architecture, electronic structure (electron affinity and ionization potential), thin film processing, thermal stability, morphology, and electron mobility of diverse organic ETMs are discussed and related to their effectiveness in improving OLED performance (efficiency, brightness, and drive voltage). Some issues relating to the experimental procedures for the estimation of relevant material properties such as electron affinity and electron mobility are discussed. The design of multifunctional electroluminescent polymers whereby light emission and electron- and hole-transport pro...

Electron Transport Materials for Organic Light-Emitting Diodes

The present invention provides a heterocyclic compound and an organic light-emitting device including the heterocyclic compound. The organic light-emitting devices using the heterocyclic compounds have high-efficiency, low driving voltage, high luminance and long lifespan.

Organic light-emitting device

Spiro Compounds for Organic Optoelectronics

Provided is an organic electroluminescence device having high luminous efficiency, high heat resistance and an extremely long lifetime. The organic electroluminescence device of the present invention includes an organic thin film layer composed of one or more layers containing at least a light emitting layer is interposed between a cathode and an anode. The light emitting layer includes a compound containing a condensed ring and a luminescent metal complex capable of emitting light having a red-based color. It is preferable that the compound containing a condensed ring includes a host material, while the luminescent metal complex capable of emitting light having a red-based color includes a phosphorescent dopant.

Organic Electroluminescent Device

Blue organic light-emitting diodes (OLEDs) can play a critical role in the field of organic electroluminescence (EL). As the most important applications of OLEDs, both new generation full-color flat-panel displays and future energy-saving solid-state lighting sources require blue color EL to fulfill their functions properly. However, considerable challenges still exist in searching for highly efficient, color stable, and long-lifespan materials and devices that emit blue color, especially in the development of deep-blue emitters, which are indispensable for high-quality displays and lighting sources. Encouragingly, great progress has been made in the area of deep-blue OLEDs in recent years with continuous efforts made by scientists, who are responsible for the significant achievements in the field of OLEDs. Hence, in this review, the crucial tactics employed to obtain high performance deep-blue emitters are presented, including polymers, dendrimers, small organic molecules, delayed fluorescent systems, and phosphorescent emitters. Moreover, the future perspectives and ongoing challenges of this research frontier are also highlighted.

Recent advances of the emitters for high performance deep-blue organic light-emitting diodes

Novel ter(9,9-diarylfluorene)s were synthesized by a Suzuki-coupling reaction of 2-bromofluorene (1) and 2,7-fluorenediboronic ester derivatives (3) with high isolated yields (63−86%). The X-ray structure analysis of ter(9,9‘-spirobifluorene) (4aa) revealed that the conjugated chromophore adopts a helical conformation. This conformation effectively releases the steric interaction between the fluorene moieties and prevents inter-chromophore interactions. The introduction of aryl groups at the C9 position of fluorene was highly beneficial to the thermal and morphological stability of these oligomers. These terfluorenes exhibit intense blue fluorescence with excellent quantum yields both in solution (∼100%) and in solid state (66−90%), and possess interesting reversible redox properties. Highly efficient blue light-emitting OLED devices were fabricated using 4aa and 4cc as emitters as well as hole transporters. The devices exhibit low turn-on voltage (∼3 V) and high EL external quantum efficiency (2.5−3%).

Ter(9,9-diarylfluorene)s: highly efficient blue emitter with promising electrochemical and thermal stability.

A high-reflectivity bottom anode is essential for high-performance top-emitting organic light-emitting devices (OLEDs). Ag has the highest reflectivity for visible light among all metals, yet its electronic properties are not ideal for anodes of OLEDs. In this letter, we report that by inducing a thin silver oxide at the surface of Ag, hole injection from Ag anodes into OLEDs is largely enhanced yet with rather high reflectivity retained. Top-emitting devices using such surface-modified Ag anode show device characteristics competitive with those of a bottom-emitting device using the indium tin oxide anode.

Top-emitting organic light-emitting devices using surface-modified Ag anode

Top-emitting organic light-emitting devices (OLEDs) have a few technical merits for active-matrix OLED displays. Generally stronger microcavity effects inherent in top-emitting OLEDs, however, complicate optimization of device efficiency and other viewing characteristics. In this letter, using the rigorous classical electromagnetic model, we analyze emission characteristics of top-emitting OLEDs as a function of device structures. From the comprehensive analysis, trends in the dependence of emission characteristics on device structures are extracted, and accordingly, a general methodology for optimizing viewing characteristics of top-emitting OLEDs for display applications is suggested. The effectiveness of the analysis and the methodology is confirmed by experimental results.

Methodology for optimizing viewing characteristics of top-emitting organic light-emitting devices

PROBLEM TO BE SOLVED: To provide a transparent cathode having high light transmittance, excellent in conductivity and easy to manufacture, and an anode structure in which a Fermi level matches with the level of an organic EL hole transport material, in an organic electoluminescent element SOLUTION: This organic electroluminescent element has a substrate, a first electrode structure installed on the substrate and provided with at least one metal layer and an opaque metal oxide layer, an organic layer installed on the electrode structure, and a second electrode structure installed on the organic layer The first electrode is an anode, and the opaque metal oxide layer is a silver oxide The second electrode structure has a transparent dielectric layer of a high refraction index as a main component, and all materials used can be deposited by a thermal vapor deposition method COPYRIGHT: (C)2005,JPO&NCIPI

Organic electroluminescent element

An organic light emitting diode is provided. The organic light emitting diode includes a substrate, an electrode structure formed on said substrate, an organic layer formed on said electrode structure and a transparent electrode structure having at least one transparent dielectric layer with a relatively higher refraction index and deposited on said organic layer by thermal evaporation.

Ping-Yuan Hsieh

Papers

Ter(9,9-diarylfluorene)s: highly efficient blue emitter with promising electrochemical and thermal stability.

Top-emitting organic light-emitting devices using surface-modified Ag anode

Methodology for optimizing viewing characteristics of top-emitting organic light-emitting devices

Organic electroluminescent element

Organic light emitting diode