Highly efficient blue light-emitting polymers containing N-(2-decyltetradecyl)carbazole[2,3-b]benzo[d]thiophene-S,S-dioxide moiety

Abstract

Abstract Blue light-emitting polymers were synthesized by Suzuki polycondensation via introducing N-(2-decyltetradecyl)carbazole[2,3-b]benzo[d] thiophene-S,S-dioxide (BTOCz) unit into the polyfluorene and polycarbazole backbone, respectively. The resulting polymers showed high thermal stability with the decomposition temperatures over 410 °C and the glass transition temperatures up to 180 °C with the increase of BTOCz content in the polymers. The lowest unoccupied molecular orbitals energy level significantly decreased, and the highest occupied molecular orbitals energy level were almost unchanged with the increasing content of BTOCz unit in the polymers. The photoluminescence quantum yields of PF-BTOCzs and PCz-BTOCzs are 45–59% and 41–54%, respectively. The device performances based on the polymers exhibited stable electroluminescent spectra with the variation of applied current densities from 100 mA cm−2 to 500 mA cm−2. The peak luminous efficiencies of 6.36 cd A−1 and 6.25 cd A−1, and the peak external quantum efficiencies of 5.03% and 4.39% with the Commission Internationale de L’Eclairage coordinates of (0.16, 0.21) and (0.17, 0.26) were obtained for PF-BTOCz30 and PCz-BTOCz30, respectively, at a turn-on voltage of 3.0 V and 2.8 V based on a single-layer device configuration of ITO/PEDOT:PSS/Emissive layer/CsF/Al. The results indicated that the strategy of introducing ambipolar BTOCz unit into the polyfluorene or polycarbazole backbone to construct the twisted molecular structure has a great potential for the development of highly efficient blue light emission.