Fluorene-based donor-acceptor-type multifunctional polymer with bicarbazole pendant moiety for optoelectronic applications

Abstract

Since limited examples are in the literature in which both organic light-emitting diodes (OLEDs) and electrochromic (EC) applications were performed using the same conjugated polymer, we presented comprehensive EC and electroluminescence (EL) studies of fluorene-based electroactive polymer (e.g., CFP6) consisting of a bicarbazole pendant moiety with quinoxaline as an acceptor bridge. CFP6 was synthesized by a Suzuki cross-coupling polymerization reaction and utilized as an active and emissive layers of the electrochromic device (ECD) and OLED, respectively, due to its high photoluminescence quantum yield intensity and fine thin film forming capability. The optical, electrochemical, cyclic voltammetry measurements, and density functional theory calculations were realized. Electrochemical cross-linking process was applied over the electroactive carbazole subunit of the CFP6 polymer. After the crosslinking process, EC performance was greatly improved. On the other hand, light emission and EL characteristics of OLEDs based on CFP6 emissive layer were realized in detail with six different device architectures to understand light output profile behavior. As a result, CFP6 emitted bright greenish yellow emission with a maximum brightness of 1777 cd/m2 at 215 mA/cm2 in the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/CFP6:%10 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP)/Alq3/LiF/Al device architecture.