Low driving voltage characteristics of triphenylene derivatives as electron transport materials in organic light-emitting diodes

Abstract

Triphenylene-based electron transport materials (ETMs), designated Bpy-TP1-4, with a coplanar molecular structure and a large electron affinity were designed and synthesized for use in organic lightemitting diodes (OLEDs). Spectroscopic ellipsometry measurements clarified that the deposited thin films of these ETMs have optical anisotropy, indicating that the molecules in the deposited thin films tend to be mostly oriented parallel to the substrate. Green OLEDs containing these ETMs allowed a lower driving voltage than that for OLEDs containing tris(8-hydroxyquinolinato)aluminum (Alq 3 ) with a random orientation. In particular, the OLED containing Bpy-TP2 showed a significantly lower driving voltage, achieving lower power consumption when compared with conventional ETMs such as Alq 3 and 1,3,5-tris(2-phenyl-1H-benzo[d]imidazol-1-yl)benzene (TPBi). Also, the operational lifetime of a blue OLED containing Bpy-TP2 is equivalent to that of an OLED with TPBi. The increased driving voltage of the device containing Bpy-TP2 is significantly suppressed compared to that of the OLED containing TPBi.

Efficient Red-Emitting Platinum Complex with Long Operational Stability

“…This enhancement was largely attributed to the high electron mobility, since the BPyTP molecules tend to adopt a fairly parallel orientation on the substrate while Alq 3 packs randomly. 48 Additionally, it should be noted that this device demonstrated an operational lifetime, LT 97 , of 284 h at an initial luminance of 1610 cd/cm 2 , and an approximate LT 97 of 638 h at 1000 cd/cm 2 , which is much better than previously reported red emitting Pt complexes. 33 Such operational lifetime performance is very close to the desirble parameters for OLED display industry, although the maximum EQE of around 10% is still far below the real potential of the state-of-the art phosphorescent materials.…”

“…The equation Φ s = Φ r ((η s 2 A r I s )/(η r 2 A s I r )) was used to calculate the quantum yields where Φ s is the quantum yield of the sample, Φ r is the quantum yield of the reference, η is the refractive index of the solvent, A s and A r are the absorbance of the sample and the reference at the wavelength of excitation and I s and I r are the integrated areas of emission bands. , Where the EML consisted of a host (either CBP, TrisPCZ, or Bebq 2 ) and PtN3N-ptb doped to 2%, 6%, or 10%, where HATCN is 1,4,5,8,9,12-hexaazatriphenylene-hexacarbonitrile, NPD is N,N′-diphyenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4″-diamine, CBP is 4,4′-bis(N-carbazolyl) biphenyl, BAlq is bis(2-methyl-8-quinolinolato) (biphenyl-4-olato)aluminum, Alq 3 is tris(8-hydroxyquinoline) aluminum, Bebq 2 is bis(benzo[h]quinolin-10-olato-κN,κO)beryllium(II), 33 TrisPCz is 9,9′,9″-triphenyl-9H,9′H,9″H-3,3′:6′3″-tercarbazole, 48 and BpyTP is 2,7-di(2,2′-bipyridin-5-yl)triphenylene. 48 Prior to deposition, the prepatterned ITO coated glass substrates were cleaned by subsequent sonication in deionized water, acetone, and isopropanol.…”

Blue organic light-emitting diodes based on phenyl-bridged fluoranthene and triphenylene derivatives

“…Among those are fluoranthene and triphenylene derivatives. Fluoranthene or triphenylene derivatives have been widely used as blueemitting materials in OLEDs due to their excellent photoluminescence (PL) and EL characteristics, as well as good thermal properties [16][17][18][19][20]. However, those have the extended aromatic surfaces, which provide the easy crystalline properties and thus reduce their EL performances.…”

Nickel-Catalyzed C-Br/C-H Bis-phenylation of Methyl 4-Bromocrotonate: A Stereoselective Entry to Methyl (E)-3,4-Diphenylbut-2-enoate

“…[8][9][10][11][12][13][14] In contrast, reports on bis-arylations are very rare and mainly restricted to aromatic electrophiles. [15][16][17][18][19] Polyarylated structures are an important class of organic compounds as they can find applications in various fields, including medicinal [20][21][22][23][24] and materials [25][26][27][28][29][30][31][32][33] chemistry.…”