Efficient near ultraviolet organic light-emitting devices based on star-configured carbazole emitters

Achieving highly efficient bipolar near-ultraviolet emitters via regulating the energy levels of the excited states by a co-acceptor system

“…[3][4][5]11 To overcome these problems, researchers have reported a variety of molecular configurations to obtain highly efficient NUV emitters. For example, (i) pure hydrocarbon aromatics featuring highly delocalized conjugated systems, which would be beneficial for charge transportation and recombination in OLEDs, while their high rigidity could enhance the thermal and morphological stabilities, which would be beneficial to improving the device duration; [12][13][14][15] (ii) introducing a heterocyclic aromatic ring with electron-donating heteroatoms into the NUV emitters to construct p-type emitters with good hole-transporting abilities; [16][17][18] (iii) construction of n-type NUV emitters by introducing electronaccepting groups, such as sulfonyl and triphenylphosphine oxide, 6,[19][20][21][22] (iv) by combining the advantages of unipolar p-type and n-type emitters in bipolar emitters for both hole and electron injection/transportation. [23][24][25][26] Compared with unipolar p-type or n-type emitters, bipolar emitters can participate in the injection/transportation of both electrons and holes, which is beneficial to charge-carrier recombination and exciton confinement in the luminescent layer.…”

Electroluminescence enhancement in ultraviolet organic light‐emitting diode with graded hole‐injection and ‐transporting structure

“…Suitable π‐conjugated material with high fluorescence efficiency and appropriate affinity energy emerges as a compromise proposal . 1,3‐bis‐(‐tert‐butylphenyl)‐‐oxadiazo‐‐ylbenzene (OXD‐7) , 4,4′‐bis(carbazol‐9‐yl)biphenyl (CBP) , TAZ , TPD and MTPC were recently reported promising UV organic emitters.…”

“…Ultraviolet (UV) OLEDs have been extensively investigated after Berggren et al reported short‐wavelength emission from PBD with an emission peak of 394 nm and an external quantum efficiency (EQE) of 0.1% . With the purpose of enhancing EL intensity and improving spectral characteristics, optimizing device structure and developing novel UV organic emitters (e.g., MTPC , SF‐DPSO and CzPySiSF ) have been intensively investigated. However, efficient UV OLEDs are still scarcely reported in comparison with visible‐wavelength devices .…”