Novel bipolar fluorescent polymers bearing N+P–O− resonance structures for fluorescent–phosphorescent (F–P) hybrid white polymer light-emitting diodes (WPLEDs)

Abstract

Two novel fluorescent polymers PPOPAF and PPOCzF, with N⁺P–O⁻ resonance structures inserted into the fluorene-alt-carbazole based backbone, were developed as blue emitters and hosts for an orange-red phosphor to realize fluorescent–phosphorescent (F–P) hybrid white polymer light-emitting diodes (WPLEDs). The polymers exhibit proper HOMO/LUMO energy levels, good thermal stability and high triplet energy (E_T) levels. Devices using PPOPAF and PPOCzF as single emissive layers show deep-blue emission with CIE coordinates of (0.16, 0.10) and (0.17, 0.10), respectively. Moreover, in hybrid white devices, doping with various concentrations of iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C²) acetylacetonate (PO-01) (0.1%, 0.2%, 0.5 wt%), the PPOCzF-based devices give a significant improvement than that of PPOPAF. While the doping concentration is 0.1 wt%, a nearly standard white emission (CIE: 0.35, 0.33) was achieved. The maximum CE, PE, EQE of PPOCzF-based devices is 4.4 cd A⁻¹, 1.1 lm W⁻¹, and 1.7%, respectively.