Diarylfluorene‐Based Organic Semiconductor Materials toward Optoelectronic Applications

Abstract

reorganizing these two types of π orbitals, thus endowing the active films with significantly different optoelectronic property. In order to design high-performance and stable conjugated molecules, some basic principles should be followed, such as electronic structure, conformation and topology, steric hindrance, as well as supramolecular interaction, which also called four fundamental nodes proposed by Huang group. [8] Particularly, steric hindrance design is an effective strategy to enhance device performance and stability via adjusting the spatial arrangement of active molecular bricks, the morphology of films, and the fine optoelectronic properties. [9,10] The sterically hindered groups are capable to rotate the dihedral angles of the adjacent monomer units, which can inhibit interchain interactions and further reduce aggregation. In addition, the rigid bulks are favorable for improving the morphological and emission spectral stability of light-emitting conjugated polymers in solid state. Besides, beyond the intrinsic electronic structures, molecular conformation and topology is a crucial for precisely tuning the physical process, controlling film morphology, device performance, and stability.Similar to the industrial manufacturing, modular production of conjugated materials enable them to present a precise electron-structure tunability, controllable structural modification, and low-cost large-scale preparation, similar to Lego building block. In the last decades, amounts of building blocks, such as fluorene, carbazole (Cz), thiophene (Th), and benzothiadiazole, have been employed to design various conjugated molecules for specific applications. [11][12][13][14][15] Among these synthons, fluorene-based bulks have been widely reported to construct high performance organic semiconductors for efficient optoelectronic devices, owing to their easy chemical modification, stable thermodynamic property, high fluorescence quantum yield, and appropriate charge transport capability. [16][17][18][19] Nevertheless, the conventional fluorene units suffer from poor color purity and luminous stability due to significantly interchain aggregation and photo-/electro-oxidation of the alkyl pendant groups at C9 position, which restricted their actual development. [20] The appearance of diarylfluorene structure provides a broader space for the design and preparation of blue emitters with higher purity and efficiency. In 1905, the simplest diarylfluorene (9,9′-diphenylfluorene) was synthesized by Ullmann and Wurstemberger for the first time. [21] As a most promise and popular alternative, diarylfluorene is a non-planar architecture

Hierarchical Nanowire Architectures Self‐Assembled from Ultra‐Deep‐Blue Fluorene‐Based Conjugated Molecules toward Organic Light‐Emitting Diodes with CIEy = 0.06

“…Finally, with the combination of a pendant Cz unit and conjugated backbone structure, [14,27] the optoelectrical properties of FCz-C8-Am were also investigated by fabricating preliminary OLEDs. First, because of the good film-forming ability of FCz-C8-Am, the average roughness of a spin-coated film from a fresh solution was approximately 0.3 nm, which was significantly different from that of the xerogels (Figure S16, Supporting Information).…”

“…We identified three other important molecular tailoring building blocks on the chemical structure of FCz‐C8‐Am. [ 14 ] The difference between FCz‐C8‐Am and FCz‐C8‐Es (together with FCz) was the symmetrical amide units at the 2‐ and 7‐sites. These were compared to reveal the influence of intermolecular hydrogen bonds (Figure S1, Supporting Information), which were mainly used as an available method to regulate the self‐assembly behavior.…”

Hierarchical Nanoarchitectonics of Ultrathin 2D Organic Nanosheets for Aqueous Processed Electroluminescent Devices

“…[ 12 ] Conversely, the high fluorescence efficiency is usually achieved by introducing bulky groups in molecular structures or diluting emitters in solid structures, which reduce low carrier mobility in integrated optoelectronic devices. [ 13 ] It is reasonable to expect that the optoelectronic devices of high performance could be achieved if high optical gain and efficient charge mobility could be reached simultaneously. To date, some organic crystalline materials have been reported to evaluate efficient integrated optoelectronic property, but most of them are still maintained in bulk crystal state.…”

Surface adhesion engineering for robust organic semiconductor devices

“…Organic semiconductors, as a class of electronic materials that feature semiconducting properties and can be used to fabricate semiconductor devices and integrated circuits, have become a research hotspot in the new century. 1–6 Compared with inorganic semiconductors, organic semiconductors, including small molecules, 7,8 polymers, 9–11 and small-molecule:polymer blends, 12,13 have obvious advantages in terms of low cost, ease of dissolving, light weight, and low-temperature processing, and have been extensively used in organic solar cells, 14–17 organic thermoelectric devices, 18–20 organic field-effect transistors, 21–24 organic light-emitting diodes, 25–28 organic sensors 29–32 and so on. More importantly, the solubility, polarity, and electrical properties of organic semiconductors can be feasibly adjusted by tailoring molecular interactions and structures, providing the necessary means to enrich the diversity of materials.…”