Synthesis and Properties of Poly(fluorene-alt-cyanophenylenevinylene)-Based Alternating Copolymers for Light-Emitting Diodes

Abstract

The novel statistical alternating EL copolymers poly[bis{2-(4-phenylenevinylene)-2-cyanoethenyl}-9,9-dihexyl-9H-fluorene-2,7-yl-alt-1,4-phenylene vinylene] (polymer I), poly-[bis{2-(4-phenylenevinylene)-2-cyanoethenyl}-9,9-dihexyl-9H-fluorene-2,7-yl-alt-2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (polymer II), and poly[bis{2-(4-phenylenevinylene)-2-cyanoethenyl}-9,9-dihexyl-9H-fluorene-2,7-yl-alt-1,4-biphenylenevinylene] (polymer III) were synthesized using modified Heck coupling reactions, and their EL characteristics were investigated. These fluorene-and cyanophenylenevinylene-based alternating copolymers, which have strong electron-withdrawing CN groups on their vinylene units, were found to be completely soluble in common organic solvents and easily spin-coated onto indium-tin oxide (ITO) coated glass substrates. The HOMO and LUMO energy levels and the electrooptical properties of these copolymers can be tuned by varying the main-chain structures and the side-chain groups. These well-defined conjugated copolymers can be synthesized with or without dialkyloxy substituents on the phenylenevinylene or biphenylenevinylene units instead of the phenylenevinylene unit; these variations in composition give rise to different emission maxima, ranging from bright yellow to a yellowish-orange color. A double-layer polymer light-emitting diode (PLED) with an ITO/PEDOT/polymer II/Al configuration exhibited a maximum brightness and luminescence efficiency of 7500 cd/m 2 at 20 V and 0.21 lm/W at 6.7 V, respectively.

Synthesis, Characterization, and Electroluminescence of Polyfluorene Copolymers with Phenothiazine Derivative; Their Applications to High-Efficiency Red and White PLEDs

“…The use of electroluminescent polymers as the emitting layers in polymer light-emitting diodes (PLEDs) has attracted considerable academic and commercial interest because of the potential of these materials as components in flat-panel displays and lighting applications. − A large number of electro- and photoactive conjugated polymers have been introduced in recent decades, such as poly( p -phenylenevinylene) (PPV), polythiophene (PT), and polyfluorene (PF) . In particular, PF and its derivatives have emerged as suitable PLED materials due to their high photoluminescence (PL) quantum efficiencies, good thermal stabilities, and amenability to functionalization at the 9-position of fluorene.…”

Synthesis of Polystyrene‐block‐Poly(methyl methacrylate) with Fluorene at the Junction: Sequential Anionic and Controlled Radical Polymerization from a Single Carbon

“…Depending on the specific monomers used, anionic, controlled radical polymerization, ROMP, and other methods have both been successfully employed in the synthesis of diblock copolymers 5–7. Diblock copolymers with a chromophore at the junction have been produced by end‐capping8–12 or the use of bifunctional molecules with remote initiation sites 13–15. In this contribution, both blocks are initiated from a single carbon, which to our knowledge has not been reported, using first anionic and then controlled radical polymerization.…”

Star-Shaped Donor-π-Acceptor Conjugated Molecules: Synthesis, Properties, and Modification of Their Absorptions Features

“…Donor-π-acceptor conjugated systems have attracted considerable attention due to their unique properties as active materials for organic electronics including organic light-emitting diodes (OLEDs), − photovoltaic cells, − nonlinear optics, − fluorescence imaging, , and memory. − Recently, substantial progress has been achieved toward understanding the structure−property relationships of such conjugated systems. ,,, Their effective charge push−pull effect depends not only on the donor (D) and acceptor (A) groups but also on the effective π-conjugation system and length between donor and acceptor groups. Photon-induced electron transfer (PET) has been largely investigated in these systems because it is a very important process in photovoltaic applications. − …”