In-situ Chemical Synthesis and Light Emitting Diodes of Non-fully Conjugated Heterocyclic Aromatic Polymer with Functionalized Multi-Wall Carbon Nanotubes
Luminescent emission of partially conjugated homopolymers was successfully demonstrated as light emitting diodes (LEDs). A series of coil-like heterocyclic aromatic poly(2,2¡¦-phenyl-5,5¡¦-bibenzimiazole) (Pbi) was synthesized and derivatized with alkyl pendants for changing the band gap to form different electroluminescence (EL) emissions.
Because of the entropy and van der Waals' interaction, multi-wall carbon nanotube (MWNT) tends to aggregate. In this investigation, chemical synthesis was applied to functionalize the MWNT. MWNT was esterificated by incorporating the functional group (-COOC10H21) to reduce its aspect ratio to facilitate its dispersion in the Pbi solution. MWNT-COOC10H21 was analyzed using Fourier transform infrared, elemental analysis, Raman spectrum and thermogravimetric analysis.
In the polymer light emitting devices, Pbi mixed with MWNT-COOC10H21 would decrease threshold voltage for about 2 V, and the device emission current was increased 5~10 times of magnitude than those of devices without MWNT- COOC10H21.
Pbi was in-situ polymerized with acidified multi-wall carbon nanotube (MWNT- COOH) for polymer LED fabrication. The emission current of these devices was still increased 10~15 times but no threshold voltage decrease compared to those of Pbi polymer solution-mixed with MWNT-COOC10H21. The polymer LED Commission International del'Eclairage chromatic indices were about the same for Pbi mixed with MWNT-COOC10H21 or in-situ polymerized with MWNT-COOH.
Advisor:Ming Chen; Shiao-Wei Kuo; Jin-Long Hong; Shih-Jung Bal
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:light emitting diodes van der waals forces aspect ratio
Date of Publication:07/12/2008