Copolymers of 2-(9H-Carbazol-9-yl)ethyl 2-Methylacrylate and 4-[5-(4-tert-Butylphenyl)-1,3,4-oxadiazol-2-yl]phenyl 2-Methylacrylate: Correlating Hole Drift Mobility and Electronic Structure Calculations with Electroluminescence

Abstract

Methacrylate monomers functionalized with pendant carbazole and oxadiazole moieties were copolymerized into random copolymers with varying carbazole/oxadiazole ratios. Specifically, the monomers of 2-(9H-carbazol-9-yl)ethyl 2-methylacrylate (CE) and 4-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]phenyl 2-methylacrylate (tBPOP) were copolymerized in various ratios, and the inherent hole drift mobilities were assessed through time-of-flight techniques. At a field strength of 345 kV/cm, the homopolymer PCE exhibited a hole mobility of 5.9 x 10(-7) cm(2)/V.s, which was approximately twice the value of the technologically important poly(9-vinylcarbazole), which exhibited a value of 2.8 x 10(-7) cm(2)/V.s. The range of hole mobilities in the copolymers varied from 2.4 x 10(-8) cm(2)/V.s for copolymers containing 50 mol % of the carbazole-containing monomer residue to 3.0 x 10(-7) cm(2)/V.s for copolymers that incorporated 88 mol % of the residue. Density functional theory (B3LYP/6-21G*) and optical absorption derived highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies of CE were -5.39 and -1.94 eV, respectively, while the corresponding oxadiazole monomer (tBPOP) had a HOMO energy of -5.99 eV and a LUMO energy of -2.23 eV. The mean luminous efficiency of coumarin 6 doped single-layer devices constructed from the poly(CE-co-tBPOP) copolymers indicated a relatively flat efficiency of ca. 0.25 cd/A over a wide carbazole mole fraction content of 0.30-0.70.

Rational design of methacrylate monomers containing oxadiazole moieties for single‐layer organic light emitting devices

“…In general, light emission tracked with the current increases. Performance of the devices was compared to both poly(MAK‐ co ‐MAO) and poly(VK 0.8 ‐ co ‐mPND 0.2 ). The device performance of the poly(VK 0.8 ‐ co ‐mPND 0.2 ) is slightly worse relative to devices based on poly(MAK 0.8 ‐ co ‐mPND 0.2 ) where the only difference between these two copolymers is the substitution of the hole transporting monomer repeat unit from VK for MAK.…”

“…A focus of this effort was to rationally design a class of MA monomers functionalized with oxadiazole moieties that will exhibit a superior spectral overlap with C6 dye. Figure presents the optical absorbance and photoluminescence of the oxadiazole monomers utilized in this study in comparison to the C6 dye; polymerizing the monomers does not alter their photophysical properties since their HOMO/LUMO orbitals are localized on the pendant groups . Using the dotted line as a guide to the eye in Figure , clearly the mNND monomer has the highest level of spectral overlap to the C6 dye, while the mPND has a decreasing level of overlap and mPND has the least.…”

Side chain engineering in π-stacked polybenzofulvene derivatives bearing electron-rich chromophores for OLED applications

“…1) is the most commonly used p-stacked polymer in the fabrication of optoelectronic devices such as OLEDs, eld effect transistors (FETs), and nonvolatile memory. 2,3 PVK shows electroluminescence, photoconductive, photorefractive, energy-donating, carrier-switching and holetransporting properties due to intrachain stacked orbitals that result from face-to-face conformation of the carbazole moieties. 2,4 Since the discovery of the spontaneous polymerization of some benzofulvene monomers, polybenzofulvene derivatives represent a new family of p-stacked polymers showing peculiar features such as the prompt and quantitative formation by spontaneous thermoreversible polymerization and the tunable solubility both in organic and aqueous media combined with interesting hole-mobility features.…”

Tuning Charge Balance in Solution-Processable Bipolar Triphenylamine-diazafluorene Host Materials for Phosphorescent Devices

“…One approache is the use of mixed hosts instead of single host, which has advantage in that charge transporting properties can be freely manipulated by changing the composition of the mixed host. , But it is difficult to choose hosts for a mixed system because many of them are immiscible, thus leading to phase separation in the film and low efficiency of devices. So an improved method is to design hosts with similar structure but with different charge balance capacity, for example, designing a host with different ratios of hole-transporting moieties to electron-transporting moieties. − …”