Bluish-Green Light-Emitting Polymers Based on Polycarbazole Containing Benzo[b]naphtho[1,2-d]thiophene-S,S-dioxide Unit

Abstract

Bluish-green light-emitting polymers (PCz-NSOs) were prepared through incorporating benzo[b]naphtho[1,2-d]thiophene-S,S-dioxide (NSO) into the main chain of polycarbazole (PCz). PCz-NSOs exhibited exceptional thermal properties with decomposition temperatures (T_ds) of PCz-NSOs surpassed 430 °C. With the NSO content increases, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PCz-NSOs gradually decreased, and the LUMO energy levels decreased more significantly, which indicated that the NSO unit possessed strong electronegativity. The combine of NSO and carbazole unit formed robust donor–acceptor (D–A) interaction, which caused the bathochromic-shift of emission spectra and present the bluish-green light emission. The high photoluminescence quantum yields (Q_PL) of PCz-NSOs were obtained with 69–82%. Even if the current density was set as 500 mA/cm², there was unchanged for electroluminescence spectrum of PCz-NSO30, exhibiting excellent spectra stability. PCz-NSO30 obtained a peak current efficiency and brightness of 5.65 cd/A and 19,061 cd/m², accompanied by CIE coordinates of (0.27, 0.53). It can be inferred that NSO held promise as an effective moiety for achieving efficient green light emission.