Noncovalent Se···O Conformational Locks for Constructing High‐Performing Optoelectronic Conjugated Polymers

Abstract

Noncovalent conformational locks are broadly employed to construct highly planar π-conjugated semiconductors exhibiting substantial charge transport characteristics. However, current chalcogen-based conformational lock strategies for organic semiconductors are limited to S···X (X = O, N, halide) weak interactions. An easily accessible (minimal synthetic steps) and structurally planar selenophene-based building block, 1,2-diethoxy-1,2-bisselenylvinylene (DESVS), with novel Se···O noncovalent conformational locks is designed and synthesized. DESVS unique properties are supported by density functional theory computed electronic structures, single crystal structures, and experimental lattice cohesion metrics. Based on this building block, a new class of stable, structurally planar, and solution-processable conjugated polymers are synthesized and implemented in organic thin-film transistors (TFT) and organic photovoltaic (OPV) cells. DESVS-based polymers exhibit carrier mobilities in air as high as 1.49 cm V s (p-type) and 0.65 cm V s (n-type) in TFTs, and power conversion efficiency >5% in OPV cells.

Aggregation‐Induced Emission of Highly Planar Enaminone Derivatives: Unexpected Fluorescence Enhancement by Bromine Substitution

“…In the past decade, the development of aggregation‐induced emission (AIE)‐active molecules with typically twist/rotor structures, which are nonemissive in dilute solution and turn to be highly emissive in the aggregate or solid states, has been a highly active research area . Planar conformation is of critical importance for organic semiconductors to enhance intramolecular charge transport and decrease bandgap because of close π–π stacking and high intermolecular orbital overlap in solid state . To achieve highly planar conformations, the intramolecular noncovalent interactions, such as hydrogen bonds, N…O, S…O, and F…S, can be served as “conformational lock” to limit the free rotation of aromatic rings, which is a widely used approach to designing organic thin film transistor (OTFT) and organic photovoltaics (OPV) materials .…”

Uncommon Aggregation‐Induced Emission Molecular Materials with Highly Planar Conformations

“…Recently, employing noncovalent intramolecular interactions to prevent the free rotation of the single bond connecting the neighboring aromatic rings has become an important strategy to achieve highly planar conformation . Upon this strategy, various high‐performing conjugated materials with highly planar conformation for organic photovoltaics and transistors have been designed and synthesized . However, the highly planar conjugated materials are barely deemed to be emissive luminogens, because planar aromatic structures enable their molecules to pack tightly in aggregates, prompting the formation of detrimental species, such as excimers, resulting in observed ACQ effect in solid state .…”

A Highly Planar Nonfullerene Acceptor with Multiple Noncovalent Conformational Locks for Efficient Organic Solar Cells

“…On the other side, noncovalent intramolecular interactions, which are well‐known as “noncovalent conformational locks,” have been employed with great successes to control conformation and construct highly planar π‐conjugated semiconductors . For example, S···X (X = O, N, and halide), Se…O, and hydrogen‐bonded noncovalent interactions have been employed to lock the conformations, promote the rigidity of the conjugated skeletons, and improve the charge mobilities of the conjugated molecules/polymers. For example, Wei and co‐workers synthesized conjugated polymers containing S···O “conformation locks” for OPVs showing PCEs of 8.2%, much higher than that of the analogous polymer‐based OPVs .…”

“…Consequently, the IDT‐BOC6‐based devices afforded a PCE of 9.6%, much higher than that of the analogous acceptor IDT‐BC6‐based ones (2.3%), which adopts a highly twisted conformation . Recently, our group synthesized novel p‐ and n‐type conjugated polymers having Se···O conformational locks for OTFT and organic photovoltaic (OPV) devices, exhibiting hole and electron mobilities as high as 1.51 and 0.64 cm 2 V −1 s −1 , respectively, and PCEs over 5% …”

“…[17] Recently, our group synthesized novel p-and n-type conjugated polymers having Se···O conformational locks for OTFT and organic photovoltaic (OPV) devices, exhibiting hole and electron mobilities as high as 1.51 and 0.64 cm 2 V −1 s −1 , respectively, and PCEs over 5%. [32] A novel nonfullerene small-molecular acceptor indacenodithiophene (IDT)-4CN is designed and synthesized with IDT as the core and benzothiadiazole and dicyanoethxylrhodanine as end-capping groups. Multiple noncovalent conformational locks N … S, CH … O, and CH … N are introduced into the backbone, resulting in a highly planar molecular acceptor.…”