Quinolyl functionalized spiro[fluorene-9,9′-xanthene] host materials with bipolar characteristics for green and red phosphorescent organic light-emitting diodes

Abstract

a b s t r a c tSpiro[fluorene-9,9 0 -xanthene] (SFX) bipolar hosts bearing one, two and three quinolyl substituents, namely SFX-bPy, SFX-DbPy and SFX-TbPy, were designed and synthesized for phosphorescent organic light emitting diodes (PhOLEDs). The successive substitution of quinoline at 2 0 , 2 and 7 0 positions of SFX results in reduced LUMO energy levels while leaving the HOMO energy levels nearly intact. The impact of quinoline substitution in these SFX-based hosts on PhOLED performance was investigated in detail through green and red model devices. For the green emitting devices, the device based on SFX-bPy host showed better performance (23.6 cd A À1 , 23.4 lm W À1 , 6.3%) due to high triplet energy level (T 1 ) and balanced carriers-transporting ability. In contrast, for the red PhOLED devices, the device hosted by SFXDbPy displayed higher performance (15.8 cd A À1 , 16.0 lm W À1 , 9.1%), attributable to the well matched T 1 and separated frontier molecular orbitals. This work thus sheds light on the rational design of SFX-based bipolar hosts for more efficient PhOLEDs.

Direct synthesis of spirobifluorenes by formal dehydrative coupling of biaryls and fluorenones

“…Furthermore, the reaction accommodated the synthesis of spiro[fluorene-9,9′-xanthene] from the diaryl ether (3pa), which receives significant attention as the core structure in the design of organic electronics and light emitting devices. 13 …”

“…† While a related structural motif was generally prepared from prefunctionalised terphenyls such as diiodoterphenyls and indenofluorenedione, 17 the present carbon dication strategy enables the direct use of relatively simple precursor 1x. The double spirocyclisation reaction was applicable to the diaryloxynaphthalene 1y, and fused spirofluorenexanthene 3ya of potent interest in materials chemistry 13 was obtained regioselectively in a synthetically acceptable yield.…”

Unraveling the Position Effect of Spiroxanthene-Based n-Type Hosts for High-Performance TADF–OLEDs

“…Based on our research interest in exploiting SFX for high-performance optoelectrical materials [ 27 , 31 , 32 ] and inspired by a current n-type host structure of SF3-TRZ for TADF-OLEDs [ 18 , 25 , 33 ], we employed a TRZ unit to functionalize the xanthene moiety of SFX. Except for endowing the hosts with n-type characteristics, there are two points to be considered for the modification.…”

Phosphorylation amplified asymmetry of spiro[acridine-9,9′-xanthene] hosts for efficient blue and white thermal activated delay fluorescent diodes

“…In contrast to symmetric host systems, 46–49 asymmetric structures 50–54 with bipolar characteristics were competent to be high-performance TADF hosts with balanced carrier injecting/transporting abilities, in addition to amplified steric hindrance for suppressing triplet quenching effects. In our previous works, 55–58 spirocyclic cores and steric phosphine oxide (PO) groups were integrated to develop a series of efficient host matrixes for blue and white TADF diodes.…”