Blue Solid-State Photoluminescence and Electroluminescence from Novel Poly(para-phenyleneethynylene) Copolymers

Abstract

We report the synthesis of a series of random copolymers composed of phenyleneethynylene and 3,7-di-tert-butylnaphthalene units by alkyne metathesis with simple catalyst systems, formed from Mo(CO) 6 and 4-chlorophenol in situ. These novel copolymers give rise to efficient (Φ ) 0.16-0.76) blue solid-state emission (λ max ) 422-443 nm) which can be fine-tuned according to their naphthalene content differing greatly from that of standard dialkyl-PPE (λ max 500-520 nm). The effective and blue-shifted solid-state emission is a result of disrupting the solid-state alignment thereby diminishing π-π interactions of the copolymers in addition to the efficient interruption of planarization of the conjugated backbone. Electroluminescent multilayer devices showed low turn-on voltages (5.5 V) and a maximum brightness of 100 cd/m 2 .

Photophysical and Electroluminescent Properties of Hyperbranched Polyfluorenes

“…The red-shift in PL resulting from chromophore aggregation in solvent/non-solvent mixture is similar to previous work. [24,25] However, the spectral red-shift and shape change in this case are not so remarkable as that observed in a solution of linear conjugated polymers. This might be due to the rigidity and large molecular size of the hyperbranched polyfluorene which does not favor excimer formation.…”

Saturated Red Light‐Emitting Copolymers of Poly(aryleneethynylene)s with Narrow‐Band‐Gap (NBG) Units: Synthesis and Luminescent Properties

“…To the best of our knowledge, it is the first time to realize the saturated red emitting OLED device using the PAEs materials. [18][19][20][21][22][23][24][25][26] Relatively low device efficiencies for this series copolymers might be partially due to low HOMO levels of these polymers ( Table 2). As indicated by the CV measurement, the HOMO level of PFE-DBT copolymers is located around 5.6 eV toward vacuum level.…”

“…As a result the external quantum efficiencies of numerous devices from PPEs are disappointing (from <0.001 to 0.15%). [18][19][20][21][22][23][24][25][26] For example, Zhan et al [25] synthesized poly(fluoreneethynylene) copolymers with bulky comonomer such as tetraphenyldiaminobiphenyl (TPD) or dihexyloxy-binaphthyl (BN). The resulted copolymers emit good green light (510 nm) with an electroluminescence (EL) external quantum efficiency of 0.007% and a brightness of 30 cd Á m À2 at a bias voltage of 27 V due to successful depression of aggregation emission.…”

“…The resulted copolymers emit good green light (510 nm) with an electroluminescence (EL) external quantum efficiency of 0.007% and a brightness of 30 cd Á m À2 at a bias voltage of 27 V due to successful depression of aggregation emission. Pschirer et al [26] also reported the copolymerization of phenyleneethynylene and 3,7-di-tertbutylnaphthalene via alkyne metathesis in order to depress both interchain interaction and planarization. The EL emission of devices based on these copolymer is blueshifted from peak emission l max ¼ 472-428 nm, with external quantum efficiency of 0.1-0.15%, as the naphthalene molar ratio increases.…”

The ADIMET Reaction: Synthesis and Properties of Poly(dialkyl para phenyleneethynylene)s

“…Subsequently, Weder [66,67] and Neher and Bunz [68] reinvestigated PPEs as active emitter layers in OLEDs. According to both groups, there are big differences between PPEs and PPVs, and one reason for the poorer performance of the PPEs is the unsatisfactory hole injection.…”