Understanding the molecular gelation processes of heteroatomic conjugated polymers for stable blue polymer light-emitting diodes

Abstract

Designing optoelectronic properties using heteroatomic conjugated polymers (HCPs).

Photophysical and Fluorescence Anisotropic Behavior of Polyfluorene β-Conformation Films

“…Conjugated polymers are materials that have demonstrated use for emerging optoelectronic applications. − The sp 2 p z orbital hybridization and overlap of the carbon atoms along the conjugated backbone afford chain effective and enhanced delocalization of the electronic wave functions, which can control the polymer properties of charge-transport and neutral excited species . Consequently, programmable chain conformation is a key tool to control their optical and electronic properties, such as absorption, emission, and conductivity, and especially allow for their anisotropy because of the intrinsic directional p-orbital overlap and π-electron delocalization along the conjugated backbone. , Besides, conjugated polymers are weakly bonded macromolecules with numerous degrees of conformational freedom with various angles between adjacent conjugated monomers, resulting in different chain arrangements varying from completely amorphous, semiordered, to crystalline structures. − In this regard, the capacity to control the degree of chain order and molecular conformation is a key component to exploit the anisotropic properties of these materials. Previously, the planar conformation adopted by some conjugated polymers was investigated as an alternative to achieve molecular alignment and regular molecular crystalline structure in solid-state systems. − These rigid coplanar structures in the solid state can also increase the effective conjugation length and suppress the nonradiative decay and excited polaron formation with improved photon absorption and emission properties. − In this work, our interest is to explore the effect of planar conformational transition and chain oriented arrangement in a conjugated polymer on the photophysical and anisotropic properties studied via time-resolved and steady-state spectroscopic measurements.…”

Supramolecular Cross-Linking and Gelation of Conjugated Polycarbazoles via Hydrogen Bond Assisted Molecular Tweezer/Guest Complexation

“…Because of the synergistic integration of electron donor–acceptor and hydrogen-bonding interactions, alkynylplatinum­(II) terpyridine molecular tweezer 1 displays sufficiently strong binding affinity toward NH -type carbazole guest ( K a : 10 4 –10 5 M –1 ). Hydrogen-bond-enhanced recognition − can be further applied to the noncovalent complexation between molecular tweezer receptors 1 , 2 and polycarbazole guest 3a . Considering the structural similarly for N- alkylated and NH -type carbazole monomers on 3a , highly specific recognition between NH -type monomers and 1 shows promising prospects for information storage and processing .…”

Intrinsically Stretchable and Stable Ultra‐Deep‐Blue Fluorene‐Based Polymer with a High Emission Efficiency of ≈90% for Polymer Light‐Emitting Devices with a CIEy = 0.06

“…[ 23 ] Preparation of a reversible aggregate network in solid states is the key object in the former two methods, [ 8,17 ] but the insulated matrix also allows for an elastic behavior in a blended system. [ 23 ] However, for light‐emitting polymers, the dynamic aggregate network assisted by interchain interlock always induces multi‐chromophores excited emission with the distributed narrow band‐gap, compared to the individual ones, [ 20,30–39 ] which is very undesirable for the constructing high performance and stable blue light‐emitting devices. [ 21,30,31,39–41 ] Therefore, how to balance the intrinsic flexibility and efficient deep‐blue emission of a spin‐coated film is a challenge to fabricate stable and efficient flexible optoelectronic devices.…”

“…[ 21,45–47 ] However, green‐band emission at ≈500–600 nm observed in film state is the major obstacle to realize the practical application in printed solid light and information display, which can be easily caused by the intermolecular electron coupling assisted by the electrostatic and ππ interaction. [ 30–33,35,37,38,48–50 ] This terrible situation is seriously deteriorating in the traditional softened LEPs with low glass transition temperatures, which are easily caused by interchain aggregation under device operation (Joule self‐heating). [ 51 ] Herein, inspired by natural polymers, we introduce a series of flexible segments (oxyalkyl chains) into the main chain to not only construct a strong interchain interpenetrated network toward intrinsic stretchability, but also realize a single‐chromophore excitonic behavior to obtain outstanding and stable ultra‐deep‐blue emission ( Scheme a,b).…”