Abstract
A new series of two-dimensional statistical conjugated polymers based on aniline and 9,9-dihexylfluorene as donor units and benzo- or naphtho-quinoxaline/thiadiazole derivatives as acceptor moieties, possessing PANI segments as side chains, were designed and synthesized. To investigate the effects of the perpendicular PANI branches on the properties of the main chain, the optical, electrochemical, morphological and electroluminescence properties were studied. The 2D materials tend to possess lower molecular weights and to absorb and to emit light red-shifted compared to the trunk 1D-polymers, in the yellow-red region of the visible spectrum. The 1D- and 2D-conjugated polymers present optical band gaps ranging from 2.15–2.55 eV, HOMO energy levels between −5.37 and −5.60 eV and LUMO energy levels between −3.02 and −3.29 eV. OLED devices based on these copolymers were fabricated. Although the performances were far from optimal due to the high turn-on voltages for which electroluminescence phenomena occur, a maximum luminescence of 55,100 cd/m2 together with a current density of 65 mA/cm2 at 18.5 V were recorded for a 2D-copolymer, PAFC6TBQ-PANI.
Highlights
Tremendous progress has been achieved in the development of conducting polymers (CPs) over the last couple of decades, due to their potential applications in optoelectronics fields such as organic solar cells (OSCs) [1,2,3,4], organic field-effect transistors (OFETs) [5,6,7] and organic light-emitting diodes (OLEDs) [8,9,10,11], among others
This study provides a starting point for a new class of 2D-materials and motivates future researches regarding the modification or improvement of the chemical structures of 2D-CPs, to produce OLED devices based on them with better performances
As shown in Scheme 1, the 1D-conjugated copolymers were synthesized through a Suzuki polycondensation by using 1.00 eq of FC6B, 0.50 eq of AniBr and 0.50 eq of the respective acceptor unit
Summary
Tremendous progress has been achieved in the development of conducting polymers (CPs) over the last couple of decades, due to their potential applications in optoelectronics fields such as organic solar cells (OSCs) [1,2,3,4], organic field-effect transistors (OFETs) [5,6,7] and organic light-emitting diodes (OLEDs) [8,9,10,11], among others. Since each of these fields requires CPs with a specific set of both physical and electrochemical features, several structural modification approaches have been used to modulate their properties. CPs with free amino groups would allow their subsequent functionalization, tuning their optical and electronic properties by covalently attaching azo dyes or imine-chromophores or growing polyaniline (PANI) chains onto their backbones, generating a two-dimension (2D)-conjugated polymer. 2D-CPs have demonstrated several interesting features, such as high hole-transporting properties, isotropic charge transport and ICT, and have shown better photovoltaic performances in comparison with the polymers without conjugated side chains [16,23,24,25,26]
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