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 copolymer (PBTML). PBTML PLED yielded reddish EL (emission of 620 nm) with peak efficiencies of 0.61% (0.89 cd/A) and a maximum electroluminance of 1290 cd/m2. A rare fluorene copolymer of a 3,4-diphenylmaleimide−thiophene−fluorene triad (PFTML) emitted orange-red photoluminescence (PL) at a of 598 nm in solution and of 601 nm in a solid thin film, with relatively high fluorescence quantum yields of 37 and 22%, respectively. Its PLEDs yielded bright orange-red EL (emission of 614 nm) with a high intensity of over 2000 cd/m2 and an enhanced peak luminous efficiency of 1.25 cd/A or an external quantum efficiency of 0.74%.

Photophysical properties and quantum chemical studies of poly(2,7-9,9'-dihexylfluorene-dyil)

“…These emission spectra have a vibronic structure partially resolved as usually observed for fluorene-based polymers. [2][3][4][5][6][7][8][10][11][12][13][14][15][16][17] Furthermore, the emission profile is similar for all solvents with small spectral shifts (λ max = 415 nm for chloroform, λ max = 412 nm for toluene, λ max = 414 nm for THF and λ max = 416 nm for ethyl acetate). Table 1.…”

“…[1][2][3][4][5][6][7][8] Several of them are also electroluminescent materials. 1,[4][5][6][7][8][9] The backbone of fluorene-based polymers contains a rigidly planar biphenyl structure which can be functionalized in the C-9 position to enhance the polymer solubility. Nevertheless, this substitution at C-9 induces minor steric effects in the adjacent aromatic rings, 10 leading, in general, to small geometrical disturbance.…”

“…[2][3][4]22,23 The reason for such differences is the occurrence of aggregation process that influences not only the spectral profile but also the emission intensity. In particular for conjugated polymers which undergo photo and electroluminescence, [1][2][3][4][5][6][7][8][9] it has been observed in several cases that both emissions are very similar, and thus the knowledge of the solid state emission is important. Here we compare the spectral profile of PHF in solid state and in dilute solutions in an attempt to identify the lumophores responsible by the emission.…”

Synthesis and photovoltaic properties of a series of bulk heterojunction solar cells based on interchain-linked conjugated polymers

“…Maleimide polymers are well-established red emitters in polymer light-emitting devices. 51,52 Moreover, a low-band gap polymer providing high charge mobility is a good choice for use as the electron-donating polymer when preparing PSCs exhibiting efficient photon-to-charge conversion. Therefore, we chose maleimide-thiophene copolymers as electron-donating polymers for our PSCs.…”

Synthesis and properties of N-substituted maleimides conjugated with 1,4-phenylene or 2,5-thienylene polymers

“…The Suzuki-Miyaura cross-coupling of boronic acid derivatives with halide compounds by palladium catalyst and Yamamoto coupling reaction of aryl halide compounds using bis(1,5-cyclooctadiene)nickel (Ni(COD) 2 ) as zerovalent nickel complexes have been widely used because of relatively high yields and mild reaction temperatures. [6][7][8][9][10][11][12][13] N-Substituted maleimide derivatives (RMIs) and their polymers have been known to exhibit excellent thermal stability and electronwithdrawing properties based on a rigid five-membered ring in the backbone. In addition, cyclic imide derivatives and their polymers have been reported for n-type organic semiconducting materials as organic transistors.…”