Solution-Processible Blue Fluorescent Dendrimers with Carbazole/Diphenylamine Hybrid Dendrons for Power-Efficient Organic Light-Emitting Diodes

Abstract

Two blue fluorescent dendrimers named PVAC2 and PVACA have been newly synthesized and investigated, where the carbazole/diphenylamine hybrid dendron is adopted instead of oligocarbazole. Compared with the reference dendrimer PVCt3, the emission maxima of PVAC2 and PVACA are found to be red-shifted accompanied by a slight reduction of the photoluminescence quantum yield in films. Most importantly, the highest occupied molecular orbital level is elevated from −5.35 eV of PVCt3 to −5.20 eV of PVAC2 and −4.95 eV of PVACA. Because of the favored hole injection, the turn-on voltage is accordingly decreased from 3.6 to 3.2 and 2.6 V. The value of PVACA is even lower than the theoretical limit of 2.78 V. In addition, PVAC2 exhibited the best nondoped device performance, showing a nearly doubled power efficiency of 4.80 lm/W relative to PVCt3 (2.37 lm/W). The results clearly indicate that dendron engineering is also a promising strategy to develop solution-processible blue fluorescent dendrimers capable of being used for power-efficient organic light-emitting diodes.

Electronic properties of carbazole/biphenylamino functionalized sulfone‐based host materials

“…[22,23] Although great efforts have been made to design and characterize host materials for the emissive layers of phosphorescent OLEDs, appropriate organic materials for blue emissive dopants still be a particularly challenging task because of requirement of high triplet excitation energy. [24,25] Carbazole [26][27][28] and dyphenylamine [28,29] derivatives are widely used as host materials in OLEDs although issues associated with the lowering of device operating voltage or device efficiency still exist. For example, 4,4 0bis(N-carbazolyl)-1,1 0 -biphenyl (CBP), which has excellent hole transport properties and a high triplet energy gap, is a carbazole-based host material commonly used as red and green phosphorescent emitters.…”

“…Carbazole [ 26–28 ] and dyphenylamine [ 28,29 ] derivatives are widely used as host materials in OLEDs although issues associated with the lowering of device operating voltage or device efficiency still exist. For example, 4,4′‐bis( N ‐carbazolyl)‐1,1′‐biphenyl (CBP), which has excellent hole transport properties and a high triplet energy gap, is a carbazole‐based host material commonly used as red and green phosphorescent emitters.…”

Synthesis and Properties of Short-Lifetime Thermally Activated Delayed Fluorescence Materials

“…The delayed lifetime of TADF materials is in the range of hundreds of microseconds as a result of their endothermic RISC process . Most of TADF materials reveal a long delayed fluorescent lifetime, , which leads to enhancement of the triplet-related nonradiative process, − such as triplet–triplet annihilate (TTA), triplet-polaron annihilate (TPA), and severe efficiency roll-off at a high current density.…”

Low-generation fluorescent polyurethane dendrimers via late-stage modification using azide–alkyne click chemistry

“…For this reason, photoactive dendrimers can be utilized as light-harvesting materials in organic light-emitting diodes (OLEDs). 8,9 Changes in the photophysical properties of uorescent dendritic molecules, on the other hand, can be exploited for sensing applications. 10,11 Additionally, luminescence signals can be traced to obtain useful information during drug delivery 12 and biological imaging.…”