Synthesis, optical and electrochemical properties of luminescent polymers containing 1,2-diphenylmaleimide and thiophene segments

• Published in: Polymer (Guilford) Vol. 46; no. 23; pp. 10383 - 10391
• Main Authors: Liu, Ting-Zhong, Chen, Yun
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 14.11.2005; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Light-emitting diodes; Organic polymers; Photoluminescence; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Synthesis; Light-emitting diodes; Synthesis; Photoluminescence; Terpolymer; Voltage current curve; Solution polycondensation; Electron affinity; Electroluminescence; Maleimide derivative copolymer; Thiophene copolymer; Experimental study; Thermal stability; Light emitting diode; Luminance; Electrochemical properties; Conjugated copolymer; Optical properties; Preparation; Aromatic copolymer; Ionization potential; Phenylene copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2005.08.058

In an attempt to balance energy barriers of hole and electron injection we prepared and characterized homopolymer containing electron-transporting 1,2-diphenylmaleimide chromophores ( P1) and copolymers consisting of 1,2-diphenylmaleimide and hole-transporting 2,5-thiophene moieties ( P2, P3) via dehalogenation polycondensation. The copolymers are amorphous materials with decomposition temperature greater than 450 °C. Absorption and fluorescence spectra were employed to investigate their optical properties both in solution and film state. Photoluminescence maxima of P1, P2 and P3 films are 564, 559 and 558 nm, respectively. The HOMO and LUMO energy levels have been estimated from their cyclic voltammograms. The HOMO levels of P1, P2, and P3 were readily raised with increasing thiophene content (−5.99, −5.59, and −5.43 eV, respectively), whereas their LUMO levels were very similar (−3.61 to −3.65 eV). Double-layer light-emitting diodes (Al/PEDOT:PSS/ P1– P3/ITO) were fabricated to evaluate their optoelectronic characteristics. Incorporation of thiophene units successfully reduced the turn-on electric field from 11.0×10 5 to 2.9×10 5 V/cm, but it decreased the luminescent efficiency and the maximum brightness.