Boosting the performance of sky-blue fluorescent OLEDs based on DPA-containing electron-transporting materials with a "V-shaped layout of triplet energy levels"

• Published in: Materials chemistry frontiers 2019-05, Vol.3 (5), p.812-82
• Main Authors: Ye, Shaofeng, Guo, Runda, Xiang, Songpo, Zhang, Qing, Lv, Xialei, Liu, Wei, Fan, Lianwei, Leng, Panpan, Sun, Shuaiqiang, Wang, Lei
• Format: Article
• Language: English
• Subjects: Anthracene; Current efficiency; Efficiency; Electron mobility; Electron transport; Energy levels; Fluorescence; Layouts; Maximum power; Organic light emitting diodes; Power efficiency; Quantum efficiency; Thermal stability
• ISSN: 2052-1537; 2052-1537
• DOI: 10.1039/c8qm00673c

Here, using a strategy called "V-shaped layout of triplet energy levels ( E T s)", a high- T 1 , electron-deficient and bulky 1,5-diazarcarbazole ( 15NCz ) was first introduced for the construction of new electron-transporting materials (ETMs). When 9,10-diphenylanthracene (DPA) was encapsulated by 15NCz at different positions, a series of ETMs with high electron mobility and good thermal stability were designed and synthesized: 9-(4-(9-([1,1′-biphenyl]-4-yl)anthracen-10-yl)phenyl)-9 H -1,5-diazarcarbazole ( p -S15NCzDPA ), 9-(3-(9-([1,1′-biphenyl]-3-yl)anthracen-10-yl)phenyl)-9 H -1,5-diazarcarbazole ( m -S15NCzDPA ), 9,10-bis(4-(9 H -1,5-diazarcarbazole-9-yl)phenyl)anthracene ( p -D15NCzDPA ) and 9,10-bis(3-(9 H -1,5-diazarcarbazole-9-yl)phenyl)anthracene ( m -D15NCzDPA ). When these novel ETMs were used in triplet-triplet fusion (TTF) fluorescent OLEDs, they exhibited superior performance compared to devices using the common ETMs TPBi and TmPyPB. In particular, devices based on m -S15NCzDPA and m -D15NCzDPA offered a maximum luminance ( L max ) of 66 100 and 66 950 cd m −2 , maximum current efficiency (CE max ) of 17.40 and 17.20 cd A −1 , and maximum power efficiency (PE max ) of 12.20 and 11.70 lm W −1 with a maximum external quantum efficiency (EQE max ) of 9.00% and 8.66%, respectively. More importantly, the device based on m -D15NCzDPA also achieved lower efficiency roll-offs at high luminance (roll-offs of 2.3% and 13.9% at 10 000 and 50 000 cd m −2 , respectively). This work demonstrated that a V-shaped layout of E T s strategy was beneficial for the construction of a series of high-performance ETMs. High-performance blue OLEDs were obtained based on ETMs with a "V-shaped layout of E T s" strategy.