A Fluorene−Oxadiazole Copolymer for White Light-Emitting Electrochemical Cells

Abstract

Solid-state, white light-emitting electrochemical cells (LECs) based on a fluorene−oxadiazole copolymer have been successfully demonstrated. The copolymer has a π-conjugated backbone consisting of 75 mol % fluorene and 25 mol % 5,5′-diphenyl-2,2′-bi-1,3,4-oxadiazole. 2-(2-(2-Methoxyethoxy)ethoxy)ethyl attached on the 9-C of the fluorenes was introduced to promote ionic conductivity necessary for the operation of LECs. The copolymer, synthesized by Suzuki coupling reactions, has a number-average molecular weight of 8700 and polydispersity of 2.41. The LECs were fabricated by spin-coating the copolymer admixed with lithium trifluoromethanesulfonate onto indium−tin oxide (ITO) substrate coated with poly(ethylenedioxythiophene)−poly(styrenesulfonic acid) (PEDOT:PSS). The opposite electrode was vapor evaporated aluminum. The LEC devices showed a white electroluminescence with CIE coordinates of (0.24, 0.31). The emission spectrum consisted of emissions from both the individual polymer chains and excimers. The white LECs are promising for solid-state lighting devices with a simple device structure and low-cost fabrication.

Photo- and electroluminescence in a series of PPV type terpolymers containing fluorene, thiophene and phenylene units

“…-yl)phenylamine)-4 ,4 -diyl]} [13] for LEC fabrication and the -conjugated backbone consisting of 75 mol% fluorene and 25 mol% 5,5 -diphenyl-2,2 -bi-1,3,4-oxadiazole with 2-(2-(2-methoxyethoxy)ethoxy)ethyl groups attached on the 9-C of the fluorene moieties [14]. In the majority of cases, a specific application is sought, and they are not focused on a mechanistic interpretation of the photophysical processes.…”

Synthesis and Characterization of 1,2,4-Oxadiazole-Based Deep-Blue and Blue Color Emitting Polymers

“…The PL quantum efficiencies ( f ) of polymers PFBOB and PFTOT in chloroform were found to reach as high as 1.00 for PFBOB and 0.44 for PFTOT compared with that of DPA ( f = 0.90, in chloroform) as the standard. In comparison with PFs 2 and structurally quite similar polymers containing 1,3,4-oxadiazole moiety, 12,13,19 polymer PFBOB showed quite narrow and only blue emission PL band with blue shifted emission maximum.…”

“…To overcome those issues, synthesizing light-emitting polymers showing high electron affinity (n-dope type polymers) is crucial because those polymers itself transport the electron quite well, and consequently, might offer highly efficient PLEDs without any electron transporting layer. Previously strong electron accepting 1,3,4-oxadiazole unit was incorporated in polymer main chain and the resulting n-dope type polymers were successfully used as light emitting [11][12][13][14][15][16][17][18][19] and electron transporting 20,21 layers in the PLEDs preparation. In addition, polymers containing 1,3,4-oxadiazole unit have been successfully utilized as fluorogenic chemosensors for the selective detection of metal ions.…”

Light-Emitting Electrochemical Cells: A Review on Recent Progress

“…The latter device featured a solution-processed trilayer activematerial structure, comprising two hydrophobic and electrochemically doped transport layers sandwiching a hydrophilic zwitterionic emission layer. For many applications, it is desirable with broadband white emission, and Sun and co-workers reported an LEC based on a single-emitter fluorene-oxadiazole copolymer that featured white emission, albeit with a modest efficiency of CE = 0.15 cd/A [98]. Higher white-emission efficiencies exceeding 3 cd/A have subsequently been reported from LECs based on a single CP emitter [100,114] and a CP blend [99].…”