Synthesis, Electrochemistry, and Electroluminescence of Novel Red-Emitting Poly(p-phenylenevinylene) Derivative with 2-Pyran-4-ylidene-Malononitrile Obtained by the Heck Reaction
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- 作者：Joo Hyun Kim and Hoosung Lee
- 刊名：Chemistry of Materials
- 出版年：2002
- 出版时间：May 2002
- 年：2002
- 卷：14
- 期：5
- 页码：2270 - 2275
- 全文大小：83K
- 年卷期：v.14,no.5(May 2002)
- ISSN：1520-5002
文摘
A novel red-emitting polymer, poly{1,4-phenylenevinylene-(4-dicyanomethylene-4H-pyran)-2,6-vinylene-1,4-phenylenevinylene-2,5-bis(dodecyloxy)-1,4-phenylenevinylene} (PM-PPV),was prepared by the Heck coupling reaction between 2-{2,6-bis[2-(4-bromophenyl)vinyl]pyran-4-ylidene}-malononitrile and 1,4-bis(dodecyloxy)-2,5-divinylbenzene. The EL device basedon a single-layer structure (ITO/PM-PPV/Al) showed EL emission with a maximum at 652nm and an external quantum efficiency of 0.004% at 0.12 mA/mm2, which is higher thanthat of MEH-PPV (0.0005%, at 0.15 mA/mm2) measured under the same conditions. Fromthe electrochemistry and UV-vis spectroscopy, the HOMO and LUMO energy levels of PM-PPV were figured out to be -5.44 and -3.48 eV, respectively, which are lower than those ofMEH-PPV at -4.98 and -2.89 eV, respectively. It is concluded that, by lowering the HOMOand LUMO levels in PM-PPV, the injection rates of the holes and electrons are morebalanced than in MEH-PPV. To improve the efficiency, the PPV layer was inserted betweenanode and PM-PPV layer. The device based on bilayer structure (ITO/PPV/PM-PPV/Al)showed EL emission with a maximum at 646 nm and an external quantum efficiency of0.05% at 0.18 mA/mm2. The efficiency of the bilayer device was higher than that of thesingle-layer device by 13 times. The CIE chromaticity coordinates of the bilayer device werex = 0.69 and y = 0.31, which are very close to the CIE chromaticity coordinates (x = 0.67,y = 0.33) of NTSC for the red color.