Novel Blue Electroluminescent Polymers with Well-Defined Conjugation Length

Abstract

Light emission from pale blue to greenish blue is successfully obtained from the diodes made of the trimethylsilyl-, monoalkoxy-, and dialkoxy-substituted polymers with welldefined conjugation length containing phenylenevinylene units. The conjugation length is adjusted by incorporating the nonconjugated spacer group in the backbone. The polymers are organic soluble and allow the fabrication of the light-emitting diode by spinning without further thermal processes. The fabricated devices show typical diode characteristics with operation voltages of 15-20 V, and the light is visible at the current density of about less than 0.5 mA/cm* 12 345for all three devices. The electroluminescence spectra are similar to the photoluminescence spectra and show the red shift as the electron-donation effects of the substituents become stronger. The bluest color of light emission corresponds to 470 nm for the polymer with trimethylsilyl substituent.

Synthesis of a green-emitting alternating block copolymer

“…Both copolymers display absorption spectra very similar to those of their respective model compounds as a result of the similarity in chromophores. The absorption peaks of copolymers 1 and 6 are qualitatively similar; the former has a maximum absorption at a longer wavelength because of the longer conjugation length of its chromophore, 390 nm (1) versus 370 nm (6).…”

“…There have been reports on a series of conjugated± nonconjugated copolymers (CNCPs) containing uniformly alternating conjugated rigid and nonconjugated flexible blocks which exhibit blue electroluminescence with a spectral maximum at 465 nm [3,4,5]. Zyung et al [6] and Hosokawa et al [7] reported other series of CNCPs also emitting blue light. Zhang et al [8] have shown that PPV obtained by partial conversion of the precursor polymer (a system that may also be regarded as a CNCP with a broad distribution of conjugation lengths), emitted light whose wavelength maximum was slightly blue-shifted from that of the nominally fully conjugated PPV.…”

Synthesis and Luminescent Properties of Blue Light Emitting Polymers Containing both Hole and Electron Transporting Units

“…The feasibility and processibility of large-scale application using organic polymers spurred research into the use of p-conjugated polymers in blue light emission. [4][5][6][7][8][9][10] Blue EL from poly(p-phenylene) [5] and poly(alkyfluorene) [4,6] was observed, but they showed rather poor processibility and mechanical properties for the device. Therefore, many other materials have been utilized for blue EL generation.…”

“…Nonconjugated side chain polymers, conjugatednonconjugated multiblock copolymers, and also sterically hindered conjugated polymers have been developed for blue light emission. [8][9][10] In this paper, we report the synthesis and the characterization of the light-emitting properties of new blue-light emitting polymers (POFB-MEH-PPV, POFB-PF, and POFB-PK) with electron accepting octafluorobiphenyl moieties introduced into the polymer backbone. To improve the EL efficiency and obtain blue light emission from the conjugated polymer, balanced injection of holes and electrons from each of the electrodes, and confined conjugation lengths are needed, respectively.…”

Amorphous Highly Conjugated Chemical-Vapor-Deposited Polymer Thin Films

“…Emphasis from the solution routes has been on retaining a stable amorphous structure and solubility of the polymer for processing. [1][2][3] From the CVD route, a-chlorinated or a-brominated poly(p-xylylene) was first deposited and then subsequent dehydrohalogenation converted the polymer to PPV with much crystallinity. [4] The CVD route and the properties of the PPV films have been well characterized.…”