From Solution to Thin Film: Molecular Assembly of π-Conjugated Systems and Impact on (Opto)electronic Properties

Abstract

The assembly of conjugated organic molecules from solution to solid-state plays a critical role in determining the thin film morphology and optoelectronic properties of solution-processed organic electronics and photovoltaics. During evaporative solution processing, π-conjugated systems can assemble via various forms of intermolecular interactions, forming distinct aggregate structures that can drastically tune the charge transport landscape in the solid-state. In blend systems composed of donor polymer and acceptor molecules, assembly of neat materials couples with phase separation and crystallization processes, leading to complex phase transition pathways which govern the blend film morphology. In this review, we provide an in-depth review of molecular assembly processes in neat conjugated polymers and nonfullerene small molecule acceptors and discuss their impact on the thin film morphology and optoelectronic properties. We then shift our focus to blend systems relevant to organic solar cells and discuss the fundamentals of phase transition and highlight how the assembly of neat materials and processing conditions can affect blend morphology and device performance.

Helix-Induced Asymmetric Self-Assembly of π-Conjugated Block Copolymers: From Controlled Syntheses to Distinct Properties

“…Self-assembly is an effective solution to pattern conjugated polymers. Therefore, it is necessary to incorporate a polymer with self-assembling characteristics onto the π-conjugated polymer to achieve control over the self-assembled morphologies . Although various π-conjugated block copolymers have been investigated, there have been limited reports on the block copolymers containing chiral blocks.…”

Exploring Linker-Group-Guided Self-Assembly of Ultrathin 2D Supramolecular Nanosheets in Water for Synergistic Cancer Phototherapy

“…Understanding the relationship between molecular structure and the self-assembling behaviors of monomers is the core area of supramolecular chemistry, which directs the path toward controlling and regulating the structure and functionality of supramolecular materials. – Over the past decades, π-conjugated molecule-based supramolecular nanomaterials have gained great interest owing to their attractive properties, and the precise programming organization of π-conjugated molecules is crucial to the performance of the subsequently assembled nanomaterials. – The noncovalent intermolecular interactions (hydrogen bonding, π–π and hydrophobic interactions, etc.) have been extensively employed synergistically for driving the bottom-up self-assembly of π-conjugated molecules into various nanomaterials in solution. ,, Nevertheless, a comprehensive rationale for the assembling pathway to monomer motifs is still lacking due to the fact that the outcomes of intermolecular interactions could be unpredictably varied by minor structural alterations of monomers. , Hence, it remains a major challenge to rational designing systems with predictable and controlled self-assembling behaviors, especially in the most essential solvent, water, due to additional influences from the strong and nondirectional hydrophobic interactions between π-conjugated molecules that result in severe unregulated self-aggregation. ,, …”

Group 15 Element (As, Sb, Bi)-Substituted Bibenzofurans with Noncovalent Conformational Locks for Enhanced Planarity

“…Organic compounds with extended π-conjugation are of current importance owing to their potential applications as optoelectronic materials . The extent of conjugation is readily enhanced by increasing the planarity of the π-electron system.…”