Synthesis and Characterization of 3,4-Diphenylmaleimide Copolymers That Exhibit Orange to Red Photoluminescence and Electroluminescence

Abstract

A series of newly designed 3,4-diphenylmaleimide-based π-conjugated copolymers that exhibit red fluorescence in both solution and solid state were synthesized and characterized. Bright and efficient red fluorescence in the solid state was achieved by varying the structural combination of thiophene and/or fluorene with 3,4-diphenylmaleimide fluorophore. The range of thiophene- and fluorene-derived 3,4-diphenylmaleimide model compounds revealed that thiophene moieties were effective in extending the emission wavelength to the red region, and fluorene moieties significantly enhanced fluorescence intensity. Polymer light-emitting diodes (PLEDs) fabricated from 3,4-diphenylmaleimide−terthiophene copolymer (PTTML) exhibited saturated red electroluminescence (EL) with emission of 676 nm, although the diode was inefficient and dim. TPBI (2,2‘,2‘ ‘-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole)) as the electron-transporting layer in PLEDs was found to improve the performance of 3,4-diphenylmaleimide−bithiophene...