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Fig. 11 Spiroxanthene-fused
[1,2-
b
]IF 108 [
83
]
Fig. 12 Structures of IFs 109
and 110 [
84
]
Fig. 13 IF-oligomer 111 [
85
]
This same group also investigated the use of dispiroxanthene-IF 108 in OLEDs,
finding its properties little changed from those of the dispirofluorene-IF derivatives
(Fig.
11
)[
83
].
Wong and colleagues found 109 to have a maximum power efficiency (PE
max
)of
~4.0 lumens per watt (lm/W) and external quantum efficiencies (EQE) greater than
8% when used as a red phosphorescent host with Btp
2
Ir(acac) in a phosphorescent
OLED (PhOLED) (Fig.
12
)[
84
]. The device also showed turn-on voltages of
~2.5-3.0 V. In addition, Wong's group has also synthesized 110 and used it as a
host material for a green PhOLED with ppy
2
Ir(acac), achieving a EQE of 14% and
PE
max
of
33 lm/W at 10,000 cd/m
2
with an operating voltage of 5 V.
Lee and coworkers synthesized IF-oligomer 111 (Fig.
13
)[
85
] and utilized it as a
blue dopant in the emitting layer of a blue OLED with maximum power efficiency
of 4.8 lm/W and quantum efficiency of 6.4% at 20 mA/cm
2
[
86
].
Ie et al. prepared fluorinated 6,12-dihydro-IF derivatives 112a-g in an attempt to
achieve large electron affinities (EAs) to facilitate n-type charge transport in OFETs
(Scheme
32
)[
87
]. With 112d,f,g they achieved EAs ca. -3 eV but no device
attributes were discussed.
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