Search

Hyperbranched polymers (HBPs) have attracted increasing attention owing to their distinct highly branched topological structures, resulting in unique properties and wide applications in organic semiconductors (OSCs). In this Review, recent progress in functional HBPs is outlined in the field of OSCs, including organic light‐emitting diodes (OLEDs), organic photovoltaics (OPVs), dye‐sensitized solar cells (DSSCs), and organic field effect transistors (OFETs), among others. Prospects of HBPs‐based materials in OSCs are examined. The results revealed that multi‐dimensional topologies not only regulate the electron (hole) transport but also adjust the film morphology, thereby affecting the efficiency and long life of organic electronic devices. Many studies showed the usefulness of HBPs as hole transport materials but reports dealing with n‐type and ambipolar materials are still lacking. In addition, the interchain covalent bond in hyperbranched polymers could mitigate the damage caused by stretching, conducive to building stable flexible stretchable devices with long‐term durability and good safety under harsh environmental conditions. Overall, the flexible stretchable design may enrich the applications of HBPs in organic semiconductors and provide new ideas for guiding the future design of functional organic semiconductor materials. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a spin‐allowed process in which a singlet state splits into two triplet states. Materials that enable SF have attracted great attention in the last decade, mainly stemming from the potential of overcoming the Shockley–Queisser (SQ) limit in photoenergy conversion. In the past decade, a large number of new molecules exhibiting SF are explored and many devices based on SF materials are studied, though the mechanistic understanding is still obscure. This review focuses on the recent developments of SF materials, including small molecules, oligomers, and polymers. The molecular design strategies and related mechanisms of SF are discussed. Then the dynamics of charge transfer and energy transfer between SF materials and other materials are introduced. Further, the progresses of implementing SF in photovoltaics are discussed. It is hoped that a comprehensive understanding to the SF materials, devices, and mechanism may pave a new way for the design of next generation photovoltaics. [ABSTRACT FROM AUTHOR]

Organic molecular semiconductors have been paid great attention due to their advantages of low-temperature processability, low fabrication cost, good flexibility, and excellent electronic properties. As a typical example of five-ring-fused organic semiconductors, a single crystal of pentacene shows a high mobility of up to 40 cm2 V−1 s−1, indicating its potential application in organic electronics. However, the photo- and optical instabilities of pentacene make it unsuitable for commercial applications. But, molecular engineering, for both the five-ring-fused building block and side chains, has been performed to improve the stability of materials as well as maintain high mobility. Here, several groups (thiophenes, pyrroles, furans, etc.) are introduced to design and replace one or more benzene rings of pentacene and construct novel five-ring-fused organic semiconductors. In this review article, ∼500 five-ring-fused organic prototype molecules and their derivatives are summarized to provide a general understanding of this catalogue material for application in organic field-effect transistors. The results indicate that many five-ring-fused organic semiconductors can achieve high mobilities of more than 1 cm2 V−1 s−1, and a hole mobility of up to 18.9 cm2 V−1 s−1 can be obtained, while an electron mobility of 27.8 cm2 V−1 s−1 can be achieved in five-ring-fused organic semiconductors. The HOMO–LUMO levels, the synthesis process, the molecular packing, and the side-chain engineering of five-ring-fused organic semiconductors are analyzed. The current problems, conclusions, and perspectives are also provided. [ABSTRACT FROM AUTHOR]

Organic solid‐state semiconductor lasers are attracting ever‐increasing interest for their potential application in future photonic circuits. Despite the great progress made in recent years, an organic laser from 3D chiral structures has not been achieved. Now, the first example of an organic nano‐laser from the micro‐helix structure of an achiral molecule is presented. Highly regular micro‐helixes with left/right‐handed helicity from a distyrylbenzene derivative (HM‐DSB) were fabricated and characterized under microscope spectrometers. These chiral micro‐helixes exhibit unique photonic properties, including helicity‐dependent circularly polarized luminescence (CPL), periodic optical waveguiding, and length‐dependent amplified spontaneous emission (ASE) behavior. The successful observation of laser behavior from the organic micro‐helix extends our understanding to morphology chirality of organic photonic materials and provides a new design strategy towards chiral photonic circuits. [ABSTRACT FROM AUTHOR]

Isoindigo, a classical electron‐deficient unit for organic optoelectronic materials, has been widely used in organic field‐effect transistors (OFETs) and organic photovoltaic devices (OPVs). However, several intrinsic drawbacks, such as its non‐coplanarity and weak absorption in the visible‐light region, have hindered its further development. Recently, many optimized isoindigo derivatives have been successfully applied to OFETs and OPVs. This Focus Review discusses recent progress in the structural optimization of isoindigo‐based organic optoelectronic materials and provides meaningful guidelines for the design of high‐performance isoindigo derivatives for organic electronics. Electric indigo: This Focus Review describes recent progress in the structural optimization of isoindigo‐based organic optoelectronic materials and provides guidance for the design of high‐performance isoindigo derivatives for organic electronics. [ABSTRACT FROM AUTHOR]

The regioselective transformation of heterobuckybowl trichalcogenasumanenes 1 a, b at peripheral butoxy groups afforded trichalcogenasumanene ortho-quinones 2 a, b. Compounds 2 a, b are distinct from 1 a, b in terms of their molecular geometry and electronic state; that is, they have a shallower bowl depth and show absorbance in the NIR region. The reaction of 2 a, b with diamines resulted in a variety of heteropolycycles, including molecular spoon 3 a- 6 a, planar π-systems 3 b- 6 b, and highly twisted [7-6-6]-fused systems 7 a, b. These new heteropolycycles had different optical/electrical properties: 4 a,b showed hole mobility of approximately 0.002 cm2 V−1 s−1, 6 a displayed red emission in both solution and the solid state, and 7 a, b formed tight stacks of the curved π-surface. [ABSTRACT FROM AUTHOR]

The design and synthesis of high-performance n-type organic semiconductors are important for the development of future organic optoelectronics. Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties. The PyDI derivatives are a new family of aromatic diimides that may exhibit both high electron mobility and good light-emitting properties, thus making them excellent candidates for future optoelectronics. [ABSTRACT FROM AUTHOR]

Covalent functionalization of reduced graphene oxide (rGO) was performed by using conjugated polymers with different monomers through nucleophilic addition of nitrogen anions to rGO. Three conjugated polymers containing tetraphenylethylene, carbazole, and phenyl groups were used, and as a result of π-π interactions and the 'polymer-wrapping' effect, the dispersion stability of rGO was improved. Even if the reaction site in the polymers was the same, there were great differences in the reactivities of the polymers, the dispersion stabilities of the resultant composites, and also the optical limiting (OL) performances of the resultant composites. The differences may be attributed to the π-conjugated structure and steric hindrance of the moiety in the polymer skeleton, which has scarcely been reported. Besides, the resultant rGO-P1 and rGO-P3 materials both showed excellent OL responses, even at 4 μJ. This behavior should enable their potential application in photonic and optoelectronic devices to protect human eyes or optical sensors from damage by intense laser irradiation. [ABSTRACT FROM AUTHOR]

By changing the packing motif of the conjugated cores and the thin-film microstructures, unipolar organic semiconductors may be converted into ambipolar materials. A combined experimental and theoretical investigation is conducted on the thin-film organic field-effect transistors (OFETs) of three organic semiconductors that have the same conjugated core structure of s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione but with different n-alkyl groups. The optical and electrochemical measurements suggest that the three organic semiconductors have very similar energy levels; however, their OFETs exhibit dramatically different transport characteristics. Transistors based on compound 1a or 1c show ambipolar transport properties, while those based on compound 1b show p-type unipolar behavior. Specifically, compound 1c is characterized as a good ambipolar semiconductor with the highest electron mobility of 0.22 cm2 V−1 s−1 and the highest hole mobility of 0.03 cm2 V−1 s−1. Complementary metal oxide semiconductor (CMOS) inverters incorporated with compound 1c show sharp inversions with high gains above 50. Theoretical investigations reveal that the drastic difference in the transport properties of the three materials is due to the difference in their molecular packing and film microstructures. [ABSTRACT FROM AUTHOR]