Nitrogen introduction of spirobifluorene to form α-, β-, γ-, and δ-aza-9, 9′-spirobifluorenes: New bipolar system for efficient blue organic light-emitting diodes. (September 2018)

• Record Type: Journal Article
• Authors: Wu, Peng; Zhu, Jun; Zhang, Zhen; Dou, Dehai; Wang, Hedan; Wei, Bin; Wang, Zixing
• Is Part Of: Dyes and pigments. Volume 156(2018)
• Page Start: 185
• Page End: 191
• Publication Date: 2018-09
• Subjects: Synthesis -- Photophysical property -- Organic light-emitting diodes -- Aza-9, 9′-spirobifluorenes -- Bipolar materials; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2018.03.066
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Four aza-9, 9′-spirobifluorenes (aza-SBFs) with nitrogen atom at different positions of one fluorene moiety were synthesized to study the structure-properties relationships.α-Aza-SBF andβ-aza-SBF possessed almost completely separated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), whileγ-aza-SBF andδ-aza-SBF showed overlapped HOMO and LUMO orbitals. The aza-SBFs showed excellent bipolar features and good thermal stabilities than those of SBFs. The maximum current efficiencies (CE) ofα-, β-, γ-, andδ-aza-SBF -based OLEDs were 28.8, 24.9, 25.5, and 27.2 cd/A, respectively. Compared to the SBF, all of four aza-SBFs showed better devices performances. The CE and power efficiency (PE) of OLED based onα-aza-SBF was 28.8 cd/A and 22.6 lm/W, while the SBF-based OLED was only 12.3 cd/A and 8.2 lm/W. The maximum external quantum efficiency ofα-aza-SBF-based OLED was 15.4%, which was 2.5 times than that of the SBF-based one (6.6%) due to introduction of nitrogen improving electron transporting. Novel materials based on these components and their potential applications in organic electronics were expected due to their excellent bipolar features. Highlights: α-, β-, γ-, and δ-Aza-9, 9′-spirobifluorenes were synthesized, characterized, and their physical properties were discussed. Introduction of nitrogen atom improved electron transporting ability. The efficiency of blue OLEDs was enhanced 2.5 times than that of spirobifluorene-based ones.