A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

The optoelectronic properties of polymeric semiconductor materials can be utilized for the fabrication of organic electronic and photonic devices. When key structural requirements are met, these materials exhibit unique properties such as solution processability, large charge transporting capabilities, and/or broad optical absorption. In this review recent developments in the area of π-conjugated polymeric semiconductors for organic thin-film (or field-effect) transistors (OTFTs or OFETs) and bulk-heterojunction photovoltaic (or solar) cell (BHJ-OPV or OSC) applications are summarized and analyzed.

π-Conjugated Polymers for Organic Electronics and Photovoltaic Cell Applications†

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

Although organic light-emitting devices have been commercialized as flat panel displays since 1997, only singlet excitons were emitted. Full use of singlet and triplet excitons, electrophosphorescence, has attracted increasing attentions after the premier work made by Forrest, Thompson, and co-workers. In fact, red electrophosphorescent dye has already been used in sub-display of commercial mobile phones since 2003. Highly efficient green phosphorescent dye is now undergoing of commercialization. Very recently, blue phosphorescence approaching the theoretical efficiency has also been achieved, which may overcome the final obstacle against the commercialization of full color display and white light sources from phosphorescent materials. Combining light out-coupling structures with highly efficient phosphors (shown in the table-of-contents image), white emission with an efficiency matching that of fluorescent tubes (90 lm/W) has now been realized. It is possible to tune the color to the true white region by changing to a deep blue emitter and corresponding wide gap host and transporting material for the blue phosphor. In this article, recent progresses in red, green, blue, and white electrophosphorescent materials for OLEDs are reviewed, with special emphasis on blue electrophosphorescent materials.

Recent Progresses on Materials for Electrophosphorescent Organic Light-Emitting Devices

Pyrene-based materials for organic electronics.

We report new divalent osmium complexes that feature strong red metal-to-ligand-charge-transfer (MLCT) phosphorescence and electrophosphorescence. The general formula of the complexes is Os(II)(N−N)2L−L, where N−N is either a bipyridine or a phenanthroline and L−L is either a phosphine or an arsine. New polypyridyl ligands synthesized are 4,4‘-di(biphenyl)-2,2‘-bipyridine (15) and 4,4‘-di(diphenyl ether)-2,2‘-bipyridine (16), and the 1,10-phenanthroline derivatives synthesized are 4,7-bis(p-methoxyphenyl)-1,10-phenanthroline (17), 4,7-bis(p-bromophenyl)-1,10-phenanthroline (18), 4,7-bis(4‘-phenoxybiphen-4-yl)-1,10-phenanthroline (19), and 4,7-bis(4-naphth-2-ylphenyl)-1,10-phenanthroline (20). 4,4‘-Diphenyl-2,2‘-bipyridine (21) and 4,7-diphenyl-1,10-phenanthroline (22) were also used in these studies. Strong π-acid ligands used were 1,2-bis(diphenylarseno)ethane (23), cis-1,2-bis(diphenylphosphino)ethylene (24), and cis-1,2-vinylenebis(diphenylarsine) (25). Ligand 25 is used for the first time in these typ...

Divalent osmium complexes: synthesis, characterization, strong red phosphorescence, and electrophosphorescence.

Recent progress in developing highly efficient nonlinear optical dendrimers and polymers for high-performance electro-optic (EO) devices has been reviewed. Our efforts are focused on using nanoscal...

Nanoscale architectural control and macromolecular engineering of nonlinear optical dendrimers and polymers for electro-optics

A series of cyano-containing distyrylbenzenes were synthesized as the model compounds to systematically study the effect of cyano substituents on the redox behaviors of conjugated molecules. By introducing the electron-withdrawing functional groups (cyano and dicyanovinyl) onto the phenylene ring, both electron affinity and electrochemical stability of the resulting distyrylbenzenes are greatly enhanced. The results enabled us to design and synthesize a new class of highly electron affinitive, fluorene-based copolymers with these cyano-containing chromophores as comonomers. The effects of acceptor strength and side chain on electron-transporting properties of these polymers were also investigated. By properly adjusting copolymer compositions, a combined high electron affinity and transport was achieved in a statistic copolymer, poly(fluorenebenzothiadiazole−cyanophenylenevinylene) (PFB−CNPV). An external quantum efficiency up to 0.88% and brightness as high as 4730 cd/m2 were achieved in a double-layer li...

Sen Liu

Papers

Divalent osmium complexes: synthesis, characterization, strong red phosphorescence, and electrophosphorescence.

Nanoscale architectural control and macromolecular engineering of nonlinear optical dendrimers and polymers for electro-optics

Effect of Cyano Substituents on Electron Affinity and Electron-Transporting Properties of Conjugated Polymers

Triarylamine-Containing Poly(perfluorocyclobutane) as Hole-Transporting Material for Polymer Light-Emitting Diodes

Focused microwave-assisted synthesis of 2,5-dihydrofuran derivatives as electron acceptors for highly efficient nonlinear optical chromophores