Orthogonal Solution-Processable Electron Transport Layers Based on Phenylpyridine Side-Chain Polystyrenes

Abstract

This article reports the synthesis and characterization of a series of polystyrenes containing phenylpyridine moieties as side chains. Methanol solubility of these polymers is induced if the relative pyridine content of the overall aromatic units of the side chains is larger than 0.5. This allows for orthogonal processing of multilayered organic light emitting diode (OLED) stacks fabricated from solutions. The polymers show high thermal stability due to their glass-transition temperatures ranging from 136 up to 247 °C. High triplet energies of up to 2.8 eV are obtained by combination of the side-chain aromatic rings in the meta position. The use of the methanol soluble side-chain polymers as an electron transport layer (ETL) is demonstrated in an orthogonally processed three-layer green-emitting OLED stack. When depositing the ETL from methanol, redissolution of the underlying emission layer does not occur.

Hole-Transporting Side-Chain Polymer Bearing a Thermally Crosslinkable Bicyclo[4.2.0]octa-1,3,5-trien-3-yl Group for High-Performing Thermally Activated Delayed Fluorescence OLED

“…Predominantly, the usage of an orthogonal solvent is an effective method to solve the problem of dissolution occurring in the bottom layer. − For instance, water-soluble poly­(3,4-ethylenedioxythiophene)–poly­(styrenesulfonate) (PEDOT:PSS) used as a hole-injection material can form an insoluble thin film in various organic solvents. ,,,− Moreover, poly­(9-vinyl carbazole) (PVK) used as a hole-transporting material (HTM) can control the solubility by varying its molecular weight (MW) . High-MW PVK is highly soluble in chlorobenzene but poorly soluble in toluene.…”

“…10.1021/acsami.9b03446. Synthesis, general experimental procedures, electrical properties of HODs, optical and photophysical properties, UV−vis absorption spectra, PL spectra, cyclic voltammogram, energy level diagrams, OLED device performances, and comparison of the performance using t4CzIPN as a dopant (PDF)…”

Homochiral Asymmetric‐Shaped Electron‐Transporting Materials for Efficient Non‐Fullerene Perovskite Solar Cells

“…Solution‐processable charge‐transporting materials have been extensively investigated for various optoelectronic devices including solar cells, field‐effect transistors (FETs), photodetectors (PDs), and organic and inorganic light‐emitting diodes (LEDs). In particular, the excellent solution processability of organic small molecules has allowed facile, large‐scale, low‐cost preparation of flexible devices . In most solution‐processed organic devices, however, simultaneous achievement of both high device performance and good processability is challenging because of the limited solubility of organic charge‐transporting materials, which prevents uniform film formation .…”

“…In particular, the excellent solution processability of organic small molecules has allowed facile, large-scale, low-costp reparation of flexible devices. [1][2][3][4][5][6][7][8] In mosts olution-processed organic devices, however,s imultaneous achievemento fb oth high device performance and good processability is challenging because of the limited solubility of organic charge-transporting materials, which prevents uniform film formation. [9][10][11] Many small-molecule charge-transporting materials consisting of pconjugated bridges suffer from low film-forming ability and/or poor solubility in organic solvents, owing to the strongi ntraand intermolecular interactions (e.g., p-p interactions and hydrogen bonds).…”

Alcohol‐Soluble Electron‐Transport Materials for Fully Solution‐Processed Green PhOLEDs

“…Solution‐processed OLEDs have been fabricated by using alcohol‐soluble polyelectrolytes as ETMs . However, the attachment of ionic side groups to the polymer side chains may lead to unanticipated electrochemical doping effects .…”