Self-Host Blue-Emitting Iridium Dendrimer Containing Bipolar Dendrons for Nondoped Electrophosphorescent Devices with Superior High-Brightness Performance

Abstract

A novel self-host blue-emitting iridium dendrimer, namely, B-CzPO, has been designed and synthesized via a postdendronization route, where a bipolar carbazole/triphenylphosphine oxide hybrid is selected as the peripheral dendron instead of the p-type oligocarbazole used in unipolar analogue B-CzG2. This structural modification can render B-CzPO with more balanced charge transportation relative to that of B-CzG2. As a result of the significantly reduced efficiency roll-off, the nondoped phosphorescent organic light-emitting diodes (PhOLEDs) of B-CzPO show a superior high-brightness performance, revealing a luminous efficiency of 21.2, 16.1, and 10.5 cd/A at 1000, 5000, and 10 000 cd/m, respectively. Compared with that of B-CzG2 (i.e., 7.8 cd/A @5000 cd/m), more than doubled high-brightness performance is achieved for B-CzPO. The results indicate that the design of self-host phosphorescent dendrimers with a bipolar feature will be a promising strategy to develop efficient nondoped PhOLEDs suitable for high-brightness applications including general illumination and micro displays.

Cyclometalated Ir(iii) complexes towards blue-emissive dopant for organic light-emitting diodes: fundamentals of photophysics and designing strategies

“…Dendritic approaches are still being investigated, especially for solution-processed phosphorescent OLEDs. [100][101][102][103][104][105][106] Available photophysical-and electrochemical data of 15-41 with their device performances are summarised in Table 2.…”

Organometallic Ir(III) Phosphors Decorated by Carbazole/Diphenylphosphoryl Units for Efficient Solution-Processable OLEDs with Low Efficiency Roll-Offs

“…The E HOMO values are evaluated to be −5.19, −5.18, −5.21, and −5.21 eV for 1 – 4 , respectively, from the onset oxidation potentials in CV curves. On the basis of E HOMO and optical band gaps ( E g ), the E LUMO values of 1 – 4 are calculated to be −3.01, −2.94, −2.98, and −2.98 eV (see Figure S8 in the Supporting Information). , …”

Designing Host Materials for the Emissive Layer of Single‐Layer Phosphorescent Organic Light‐Emitting Diodes: Toward Simplified Organic Devices

“…In 2016, two other non‐doped blue SL‐PhOLEDs (D86‐D87) based on dendrimer B2 and dendrimer B3 were reported. [ 106 ] Both dendrimers consist of a central bis(2,4‐difluorophenylpyridinato)‐iridium (III) core, similar to the one of FIr6, decorated by a carbazole dendron in dendrimer B2 or by a bipolar carbazole/triphenylphosphine oxide hybrid dendron in dendrimer B3. The physicochemical properties of the two dendrimers were similar suggesting that the modification of the peripheral dendrons does not affect their optical and electrochemical properties.…”