Synthesis and characterization of new 3-alkylthiophene copolymer that exhibit orange-red photoluminescence and electroluminescence
Using copolymerization functionalization, a Novel solution-processable π-conjugated 3-alkylthiophene copolymer (molar ratio of monomer 3-octylthiophene (3OT) and 3-(2-ethyl-1-hexyl) thiophene (3EHT) was 1:1) combining electrochemical properties of poly (3-octylthiophene) (P3OT) and poly (3-isooctylthiophene) (P3EHT) was synthesized by FeCl3-oxidative approach. Characterization of the polymers included FT-IR, NMR, gel permeation chromatography (GPC), thermo-gravimetric analysis (TGA), UV-Vis spectroscopy photoluminescence (PL) and electroluminescence (EL). P3OTEHT depicted excellent solubility in common organic solvents. The optical properties investigations showed that the band-gap energy of P3OTEHT was similar to P3OT (2.43 eV) at 2.45 eV and 6% lower than that of P3EHT in CHCl3 solution. The emission maxima of P3OTEHT was 50 nm blue-shifted with respect to that of P3OT. However, the PL intensity of P3OTEHT was seven times higher than that of P3OT in film. The turn-on voltage of LED (ITO/P3OTEHT/Ag) devices was approaching to P3OT (5.5 V) at 5.6 V and 1.9 V lower than that of P3EHT. The EL color of P3OTEHT was bright pure orange-red (emission λ max EL of 600 nm), meanwhile, the half-wave bandwidth was 70 nm. TGA studies showed that P3OTEHT exhibited very good thermal stabilities, losing 5% of its weight on heating to 300 °C. The results indicate that the P3OTEHT with low band-gap energy, low turn-on voltage, high photoluminescence quantum yield pure EL color and processability, and might be promising polymer materials for applications in polymer light-emitting diodes, light-emitting electrochemical cells and polymer solar cells, etc.
KeywordsPolymer Solar Cell Narrow Molecular Weight Distribution Luminescence Quantum Yield High Photoluminescence Quantum Yield Double Beam Spectro
This work was supported by the Doctor Foundation of Ministry of Education of China (20030286012) and the Foundation High-tech Item of Province in Jiang-su of China(BG 2005034).
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