Highly Improved Efficiency of Deep-Blue Fluorescent Polymer Light-Emitting Device Based on a Novel Hole Interface Modifier with 1,3,5-Triazine Core

Abstract

We present an investigation of deep-blue fluorescent polymer light-emitting diodes (PLEDs) with a novel functional 1,3,5-triazine core material (HQTZ) sandwiched between poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) layer and poly(vinylcarbazole) layer as a hole injection layer (HIL) without interface intermixing. Ultraviolet photoemission spectroscopy and Kelvin probe measurements were carried out to determine the change of anode work function influenced by the HQTZ modifier. The thin HQTZ layer can efficiently maximize the charge injection from anode to blue emitter and simultaneously enhance the hole mobility of HILs. The deep-blue device performance is remarkably improved with the maximum luminous efficiency of 4.50 cd/A enhanced by 80% and the maximum quantum efficiency of 4.93%, which is 1.8-fold higher than that of the conventional device without HQTZ layer, including a lower turn-on voltage of 3.7 V and comparable Commission Internationale de L'Eclairage coordinates of (0.16, 0.09). It is the highest efficiency ever reported to date for solution-processed deep-blue PLEDs based on the device structure of ITO/HILs/poly(9,9-dialkoxyphenyl-2,7-silafluorene)/CsF/AL. The results indicate that HQTZ based on 1,3,5-triazine core can be a promising candidate of interfacial materials for deep-blue fluorescent PLEDs.

Polystyrenesulfonate Dispersed Dopamine with Unexpected Stable Semiquinone Radical and Electrochemical Behavior: A Potential Alternative to PEDOT:PSS

“…Subsequently, the product of the reaction was purified by dialysis to remove catalyst Tris, free DA monomerm and DA-based oligomer with low molecule weight. It is interesting that DA:PSS showed a relatively lower acidity with a pH of 5.3, compared with the pH of 1.9 for PEDOT:PSS . Considering the deep brown color freeze-dried product, we proposed that DA was oxidized into new compounds.…”

“…Poly­(3,4-theylene dioxythiophene):poly­(styrene sulfonic acid) (PEDOT:PSS) is one of the most successful and excellent water-soluble p -type materials as it has advantages including tunable high conductivity, high transparency in UV–visible region, the capability of smoothing the ITO morphology and so on. − There are still some drawbacks including poor device lifetime induced by its acidity, structural and electronic inhomogeneity. Considering the weakness of PEDOT:PSS, many alternatives of PEDOT have been widely explored in previous work. − Some work related to hydroquinone–quinone complexes on molecular electronics has been reported. , Motivated by our curiosity on the potential of electron-rich aromatic phenolic compounds to act as hole-transport materials, recently we further applied phenol-based material such as lignin-based derivatives as p -type transport materials in OPVs and OLEDs for the first time. − In general, aromatic phenolic derivatives (PDs) are well-known as unstable compounds as they can be readily converted into fragile phenolic radicals (PRs); thereby, studies of their potential as p -type material are rarely reported. In fact, PDs and PRs are not as vulnerable as we postulate based on a traditional viewpoint.…”

“…In fact, PDs and PRs are not as vulnerable as we postulate based on a traditional viewpoint. To give an example, catechol can be oxidized into a semiquinone radical intermediate or quinone under mild conditions, , along with an electron transport process. − , Generally, a semiquinone radical is unstable because of its relatively high thermodynamic potential. , But in fact, for many biopolymers related to catechol, such as lignin, melanin, humic acid and tannin, stable PRs and persistent semiquinone radical were widely detected. − To sum up, there are several strategies to stabilize semiquinone radical: (1) protection of the bulky and hydrophobic tert -butyl group borne with catechol structure, (2) metalloprotein was found to have the capability of stabilizing semiquinone radical, (3) intramolecular/intermolecular hydrogen bonding between the aryloxyl radical semiquinone hinders the further loss of one electron to form quinone, (4) some heavy metals such as Zn 2+ and Pb 2+ are known to stabilize semiquinones via formation of radical complexes, − whereas some paramagnetic metal ions such Cu 2+ , Mn 2+ , or Fe 3+ are opposite, and (5) a tightly bounded three-dimensional micromulecular network of lignin can also stabilize the semiquinone radical …”

“…PSS was introduced to ensure its good water solubility and solution processability to achieve excellent film formation. Moreover, phenol-based materials showed irreversible oxidation behavior. − In contrast, PDA:PSS showed stable and quasi-reversible electrochemical oxidation behavior. Consequently, as an indium tin oxide (ITO) anode modifier, solution-processed DA:PSS film showed enhanced performance in organic light emitting diodes.…”

Color-tunable persistent luminescence hybrid materialsviaradiative energy transfer

“…Polymeric fluorescent dye (PFD) are the functional polymers which have a chromophoric center within their structure [29][30][31][32][33] . Owing to the inherent non-leaching behavior and good light fastness combined with the special properties of polymers, polymer bonded dyes or reactive dyes maybe play more important roles [34][35][36][37][38][39] .…”