Novel Soluble N‐Phenyl‐Carbazole‐Containing PPVs for Light‐Emitting Devices: Synthesis, Electrochemical, Optical, and Electroluminescent Properties

Abstract

Summary: Novel PPV derivatives (PCA8‐PV and PCA8‐MEHPV) containing N‐phenyl‐carbazole units on the backbone were successfully synthesized by the Wittig polycondensation of 3,6‐bisformyl‐N‐(4‐octyloxy‐phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT‐IR and NMR spectroscopy. The polymers (with $\overline M _{\rm w}$ of 6 289 for PCA8‐PV and 7 387 for PCA8‐MEHPV) were soluble in common organic solvents and displayed high thermal stability (Tgs are 110.7 °C for PCA8‐PV and 92.2 °C for PCA8‐MEHPV, respectively) because of the incorporation of the N‐phenyl‐carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8‐PV and 0.7 V for PCA8‐MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N‐phenyl‐carbazole units on the backbone. Both the single‐layer and the double‐layer light‐emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish‐blue or bluish‐green light (the maximum emissions located 494 nm for PCA8‐PV and 507 nm for PCA8‐MEHPV, respectively). Compared with those of the single‐layer devices, the emission efficiencies of the double‐layer devices, in which an electron‐transporting layer (Alq3) was added, were enhanced by a factor of 10, implying that the better hole‐electron balance is achieved because of the incorporation of the electron‐transporting layer.The N‐phenyl‐carbazole‐containing polymers synthesized.imageThe N‐phenyl‐carbazole‐containing polymers synthesized.

Synthesis of 2,7-Carbazolenevinylene-Based Copolymers and Characterization of Their Photovoltaic Properties

“…3-Octylthiophene, <productlargeclass>5,5′-dibromo-2,2′-bithiophene, 2,2′-bithiophene, 2-(tributylstannyl)thiophene, and 5-bromo-2-thiophenecarboxaldehyde were purchased from Aldrich and used without further purification<productlargeclass>. The synthesis of 2,7-bis(trityloxymethyl)carbazole (1) [9], 1-iodo-4-octyloxybenzene (2) [32], and 2,5-dibromo-3-3-dihexylthiophene 1,1-dioxide (16) [18b] have been described previously.…”

“…[22] Finally, HornerEmmons chemistry seems to give higher molecular weights than the standard Wittig reaction. [23] PCV, PCVT, PCVTT, and PCVTTTT were synthesized using the standard Horner-Emmons reaction using equimolar ratios of dialdehyde and compound 6 in the presence of an excess of potassium tert-butoxide in anhydrous THF. In the case of poly(N-(4-octyloxyphenyl)-2,7-carbazolenevinylene-alt-3″,4″-dihexyl-2,2′;5′,2″;5″,2″′;5″′,2″″-quinquethiophenevinylene 1″,1″-dioxide) (PCPTDO), the use of the Horner-Emmons reaction did not lead to the desired polymer.…”

The synthesis and photo-physical properties of extended styryl fluorescent derivatives of N-ethyl carbazole

“…Carbazole unit has an electron donating influence and carbazole containing dyes are known to have excellent photo-conductivity and relatively intense luminescence [4]. The thermal stability or the glass state durability of organic compounds can be greatly enhanced by the introduction of organic carbazole group in the core structure [5].…”

Synthesis and characterization of new blue light emitting alternating terphenylenevinylene carbazylenevinylene copolymer

“…The low HOMO level may be due to introduction of carbazole group with electron donating nature, which leads to a significant increase in hole injection and transport ability. 29 In order to investigate the electroluminescent property of the polymer containing carbazole and terphenylene, ITO/ PEDOT/polymer/Al device was fabricated and evaluated. Figure 4 shows the electroluminescence spectrum of ITO/ PEDOT/polymer/Al device.…”