Search

Organic semiconductors have been receiving intensive attention due to the specific advantages of low‐temperature processing ability, low‐fabrication cost, flexibility, and so forth. The charge carrier mobility of higher than 10 cm2 V−1 s−1 for organic semiconductors is of great importance to be studied since it presents a future promising research direction toward commercial microelectronic applications. With the significant progress of the discovery of novel organic molecules and the further improvements of device fabrication technology, some organic molecules can break the limit of our knowledge and show very high mobilities. In this review, organic polymers and small molecules with mobilities above 10 cm2 V−1 s−1 are first introduced to provide the readers with a general understanding of the features and characteristics of high‐performance organic semiconductors. Then, some important parameters, including the molecular structures, the device configurations, and the performance, are discussed in detail. Finally, the clues to obtain high mobility are summarized, and the perspective toward the future possible research directions are also provided.

Developing new optimized bifunctional photocatalyst is of great significant for achieving the high-performance photo-assisted Li-O2 batteries. Herein, a novel bifunctional photo-assisted Li-O2 system is constructed by using siloxene nanosheets with ultra-large size and few-layers due to its superior light harvesting, semiconductor characteristic, and low recombination rate. An ultra-low charge potential of 1.90 V and ultra-high discharge of 3.51 V have been obtained due to the introduction of this bifunctional photocatalyst into Li-O2 batteries, and these results have realized the round-trip efficiency up to 185 %. In addition, this photo-assisted Li-O2 batteries exhibits a high rate (129 % round-trip efficiency at 1 mA cm-2 ), a prolonged cycling life with 92 % efficiency retention after 100 cycles, and the highly reversible capacity of 1170 mAh g-1 at 0.75 mA cm-2 . This work will open the vigorous opportunity for high-efficiency utilization of solar energy into electric system.

Recently, anisotropic 2D materials, such as black phosphorus and rhenium disulfides (ReS2 ), have attracted a lot attention because of their unique applications on electronics and optoelectronics. In this work, the direct growth of high-quality ReS2 atomic layers and nanoribbons has been demonstrated by using chemical vapor deposition (CVD) method. A possible growth mechanism is proposed according to the controlled experiments. The CVD ReS2-based filed-effect transistors (FETs) show n-type semiconducting behavior with a current on/off ratio of ≈10(6) and a charge carrier mobility of ≈9.3 cm(2) Vs(-1). These results suggested that the quality of CVD grown ReS2 is comparable to mechanically exfoliated ReS2, which is also further supported by atomic force microscopy imaging, high-resolution transmission electron microscopy imaging and thickness-dependent Raman spectra. The study here indicates that CVD grown ReS2 may pave the way for the large-scale fabrication of ReS2-based high-performance optoelectronic devices, such as anisotropic FETs and polarization detection.

Organic–inorganic heterostructures are an emerging topic that is very interesting for optoelectronics. Here, non-conventional p–n junctions are investigated using organic rubrene single crystal and 2D MoS2 as the p- and n-type semiconducting materials, respectively. The current-rectifying behavior is clearly observed in the junction device. The rectification ratio can be electrically tuned by the gate voltage due to the 2D nature of the heterostructure. The devices also show good photoresponse properties with a photoresponsivity of ≈500 mA W−1 and a fast response time. These findings suggest a new route to facilitate the design of nanoelectronic and optoelectronic devices based on layered inorganics and organics.

The characteristics of field-effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this review together with the electronic and crystal structures of phenacenes. Phenacene molecules possess a low HOMO level and a wide band gap. The highest mobility observed in the phenacene thin-film FETs is 7.4 cm2 V–1 s–1 for [6]phenacene, and in single-crystal FETs the highest value is 6.3 cm2 V–1 s–1 for [7]phenacene. The phenacene thin-film FETs show O2-sensing properties unlike their single-crystal FETs. The bias-stress effect is fully investigated for phenacene single-crystal FETs. Furthermore, the low-voltage operation of phenacene single-crystal FETs with electric-double-layer (EDL) capacitors is reported. The temperature dependence of phenacene single-crystal FETs is reported to clarify the transport mechanism, which is suggestive of band-like transport.

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi2 S4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi2 S4 on CNT sponge, in which CoNi2 S4 nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g-1 . Meanwhile, Fe2 O3 /CNT sponge anode with specific capacitance of 460 F g-1 in a prolonged voltage window is also prepared by electrodepositing Fe2 O3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi2 S4 /CNT//Fe2 O3 /CNT) is assembled by using CoNi2 S4 /CNT sponge as positive electrode and Fe2 O3 /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg-1 at a power density of 847 W kg-1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi2 S4 /CNT//Fe2 O3 /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density.

Chemical vapor deposition growth of 1T' ReS2x Se2(1-x) alloy monolayers is reported for the first time. The composition and the corresponding bandgap of the alloy can be continuously tuned from ReSe2 (1.32 eV) to ReS2 (1.62 eV) by precisely controlling the growth conditions. Atomic-resolution scanning transmission electron microscopy reveals an interesting local atomic distribution in ReS2x Se2(1-x) alloy, where S and Se atoms are selectively occupied at different X sites in each Re-X6 octahedral unit cell with perfect matching between their atomic radius and space size of each X site. This structure is much attractive as it can induce the generation of highly desired localized electronic states in the 2D surface. The carrier type, threshold voltage, and carrier mobility of the alloy-based field effect transistors can be systematically modulated by tuning the alloy composition. Especially, for the first time the fully tunable conductivity of ReS2x Se2(1-x) alloys from n-type to bipolar and p-type is realized. Owing to the 1T' structure of ReS2x Se2(1-x) alloys, they exhibit strong anisotropic optical, electrical, and photoelectric properties. The controllable growth of monolayer ReS2x Se2(1-x) alloy with tunable bandgaps and electrical properties as well as superior anisotropic feature provides the feasibility for designing multifunctional 2D optoelectronic devices.

2D transition metal dichalcogenides are promising channel materials for the next-generation electronic device. Here, vertically 2D heterostructures, so called van der Waals solids, are constructed using inorganic molybdenum sulfide (MoS2 ) few layers and organic crystal - 5,6,11,12-tetraphenylnaphthacene (rubrene). In this work, ambipolar field-effect transistors are successfully achieved based on MoS2 and rubrene crystals with the well balanced electron and hole mobilities of 1.27 and 0.36 cm2 V-1 s-1 , respectively. The ambipolar behavior is explained based on the band alignment of MoS2 and rubrene. Furthermore, being a building block, the MoS2 /rubrene ambipolar transistors are used to fabricate CMOS (complementary metal oxide semiconductor) inverters that show good performance with a gain of 2.3 at a switching threshold voltage of -26 V. This work paves a way to the novel organic/inorganic ultrathin heterostructure based flexible electronics and optoelectronic devices.