A novel bipolar phenanthroimidazole derivative host material for highly efficient green and orange-red phosphorescent OLEDs with low efficiency roll-off at high brightness

Abstract

Highly efficient green and orange-red PhOLEDs with low efficiency roll-off enabled by a bipolar violet-blue phenanthroimidazole-based fluorophore.

Versatile Host Materials for Highly‐Efficient Green, Red Phosphorescent and White Organic Light‐Emitting Diodes

“…Compared with ICz‐PPI , one more ICz group that connected to N1‐positions of PI in 2ICz‐PPI helped to enhance the triplet energy, however, it also reduced the PLQY, which was an element to decrease device performance. Therefore, ICz‐PPI and 2ICz‐PPI are supposed to be serviceable candidates as both blue emitters and hosts for green and red PhOLEDs . What's more, to further investigate intramolecular charge transfer (ICT) characteristics of ICz‐PPI and 2ICz‐PPI , we also investigated different PL spectra of ICz‐PPI and 2ICz‐PPI in different polarity solvents.…”

“…Therefore, ICz-PPI and 2ICz-PPI are supposed to be serviceable candidates as both blue emitters and hosts for green and red PhOLEDs. [30] What's more, to further investigate intramolecular charge transfer (ICT) characteristics of ICz-PPI and 2ICz-PPI, we also investigated different PL spectra of ICz-PPI and 2ICz-PPI in different polarity solvents. As shown in Figure S1, with solvents polarity increasing from low-polarity nhexane to high-polarity methanol, there is no obvious red-shift in the emission, indicating a weak ICT interaction and it also could be efficiently suppressed both in ICz-PPI and 2ICz-PPI.…”

Ternary Acceptor–Donor–Acceptor Asymmetrical Phenanthroimidazole Molecule for Highly Efficient Near‐Ultraviolet Electroluminescence with External Quantum Efficiency (EQE) >4 %

“…We used cyclic voltammetry to investigate the electrochemical properties and determine the energy levels of PPI-2BI.A s shown in Figure 3, aq uasi-reversible oxidation and reduction process was observed with an oxidation onset potential (E ox )o f 1.12 Va sm ost PI derivatives, [12,15] and the corresponding HOMO level is calculated to be À5.54 eV.I nt he cathodic range, ap air of reversible oxidation and reduction waves resulting from the BI unit werea lso obtained (FigureS1i nt he Supporting Information). From the reductiono nset potential (E red % 1.82 V), the LUMO is À2.60 eV.I ti sn oted that this new compound, on one hand, shows ad eeper LUMO level than other PI derivatives, [24,26] indicating more efficient electron injection. This is attributed to the two electron-accepting BI groups connected tot he C2 and N1 positions of the PI unit, enhancing the electron coupling and communication.…”

“…The lowest absorption band at approximately 258 nm may originate from the p-p*t ransition of two biphenyl units connected with imidazole. [24] As trong and Scheme1.Synthetic routes and molecularstructure of PPI-2BI. wide absorption peak at approximately 315 nm and aw eak shoulderp eak at about 356 nm were observed, which should be assigned to the p-p*t ransition of the PI group and BI group.…”

Enhanced Drug Photosafety by Interchromophoric Interaction Owing to Intramolecular Charge Separation

“…[17] Integration of the photoactive pyridylpyrimidine moietyi nto am ore complex structure strongly modifies its photobehavior and leads to an improved toxicological profile of IMT.H owever,i ti sn ot clear how the intramolecular interactionb etween the different chromophores of IMT occur.I nterchromophorici nteraction is an omnipotent process that is responsible for the electron, proton, energy, and charge transfersa mongo rganic light-emitting diodes (OLED), supramolecular frameworks, metal-organic frameworks,l ight-harvestings ystems, and biomolecules. [18][19][20][21][22] Never-theless, there are few examples that unveilt he nature of an interchromophoric interaction. In an attemptt ounderstand the unexplained photobehavior of IMT and the chromophorechromophore interactions amongi ts substructure molecules (Scheme 1), an investigationh as been conducted herein by using femto-to-nanosecond transient absorption, picosecond time-resolved resonance Raman spectroscopy (ps-TR 3 ), and nanosecondt ransient resonance Ramans pectroscopy.T o better understand the photosafety of IMT,D NA was used as a model substrate to explore the photochemical reactions between IMT and DNA.…”