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Three novel rigid-rod semiconducting polymers containing fused electron-deficient PDI and IID units have been synthesized through aldol polymerization. Their unique opto-electronic properties have been investigated systematically.

Organic crystals, especially ultra-thin two-dimensional (2D) ones such as monolayer molecular crystals, are fragile and vulnerable to traditional vacuum deposition. Up to now, most of the methods reported for fabricating organic field-effect transistors (OFETs) with top-electrodes on the 2D molecular crystals are based on mechanical-transfer method. Nondestructive method for large scale in-situ electrode deposition is urgent. In this work, the silver mirror reaction (SMR) is introduced to construct top-contact electrodes on 2D organic crystalline thin films. OFETs based on bilayer crystalline films with solution-processed silver electrodes show comparable performance to devices with transferred gold electrodes. In addition to that, OFETs with SMR fabricated silver electrodes show lower contact resistance than the ones with evaporated silver electrodes. Furthermore, the temperature under which SMR electrodes annealed is relatively low (60 °C), making this approach applicable to varies of organic semiconductors, such as spin-coated polymer films, vacuum evaporated films, 2D and even monolayer crystalline films. Besides, OFETs with sub-micrometer channel width and 25 µm channel length are realized which might find practical application in the ultra-small pixel mini/micro-LEDs.

Due to their advantages of being low-cost and light weight, and having mechanical flexibility, great attention has been focused on π-conjugated organic semiconductors. Many high-performing materials have been developed in the past decade. However, constructing electron-deficient ladder-type conjugated systems is far more challenging than constructing electron-rich systems. We have successfully synthesized a series of larger and extended novel electron-deficient aza-isoindigos (AIID-12, FAIID-12, and AIID-14) with up to 14 rings. Terminal fluorine atoms and the fusion of an additional naphthalene ring are also introduced to compare the properties of the resulting compounds to those of phenyl aza-isoindigos. Compared with isoindigo, the absorption spectra of AIID-12, FAIID-12, and AIID-14 extend into the NIR region at 900 nm due to their extended conjugation systems. These fused aza-isoindigo conjugated systems exhibit excellent solubility, highly planar backbones, substantial crystallinity, tunable conjugation lengths, and optoelectrical properties. The more extensive conjugated system with higher highest occupied molecular orbital (HOMO) and unchanged lowest unoccupied molecular orbital (LUMO) energy levels shows a narrow band gap and near-infrared absorption. Thus, the enhanced electron affinities (EAs) can facilitate the realization of electron-transport properties. As a result, OTFT devices based on AIID-14 exhibit a hole mobility of 0.076 cm2 V−1 s−1 and electron mobility of 0.003 cm2 V−1 s−1. Our results demonstrate the great potential of these aza-isoindigo systems for small-molecule semiconductor use.

Critical thinking is an important part of the quality cultivation of engineering students. At present, many colleges and universities in China have gradually realized it, and mainly strengthen the training of students’ critical thinking by offering relevant humanities courses, but there are few researches related to this topic through the penetration of engineering professional courses, and they are not deep enough. This study mainly discusses the efficacy of virtual simulation system teaching method in improving critical thinking of engineering students engaged in NC (Numerical Control) machining. It integrates the types of learning activities in the proposed teaching method with the development elements of critical thinking, and then constructs the context-based teaching design along with a self-developed virtual learning environment for the cultivation of students’ critical thinking. We also evaluated students’ response towards the research topics to investigate its teaching-learning effectiveness and acceptance by student community. Responses from questionnaires were collected from a convenience sample of 63 junior students majoring in NC machining from the author’s university. The subsequent empirical study was conducted to exhibit superior results for mostly the cognitive skills of critical thinking. Students’ feedback also revealed that students obtain more satisfaction and self-confidence, and demonstrated high positive attitude towards the proposed teaching method, and showed high perceived usefulness of the context-based teaching design to acquire complete, concrete and confident knowledge of NC machining. The findings of this study are valuable for academic institutions and educators to design the virtual visualized lectures and classrooms to enhance students’ performance in critical thinking.

Rylene diimides have evolved as the most investigated compounds among polycyclic aromatic hydrocarbons, due to their excellent absorption, fluorescence and outstanding electron-withdrawing ability. In this work, we present two A–D–A type electron acceptors based on terrylene diimides and investigate the impact of intramolecular nonbonding conformational locks on the molecular geometry, the solid packing arrangement and the photovoltaic performance. Detailed investigation demonstrates that the introduction of fluoride atoms facilitates the noncovalent interactions with sulfur elements on adjacent thiophene groups and therefore, more balanced charge transfer and suppressed bimolecular recombination promotes the JSC and FF, endowing the solar cells based on fluoride-substituted acceptors with a higher PCE of up to 5.29%.

Three anthracene derivatives with asymmetric structures, namely 2-phvA, 2-pheA and 2-phA, were synthesised and characterized. Single crystal OFETs of the three compounds were fabricated. 2-pheA and 2-phA showed a mobility of 0.79 cm2 V−1 s−1 and 0.66 cm2 V−1 s−1, while 2-phvA exhibited a high mobility of 10 cm2 V−1 s−1, which was one of the highest mobilities for asymmetric anthracene derivatives. Band-like charge transport with low activation energy was observed in 2-phvA single crystal FET devices at low temperature. These results demonstrated that asymmetry can serve as an alternative strategy to design high-performance organic semiconductors.

Development of highly efficient and stable lateral organic circularly polarized light photodetector is a fundamental prerequisite for realization of circularly polarized light integrated applications. However, chiral semiconductors with helical structure are usually found with intrinsically low field-effect mobilities, which becomes a bottleneck for high-performance and multi-wavelength circularly polarized light detection. To address this problem, here we demonstrate a novel strategy to fabricate multi-wavelength circularly polarized light photodetector based on the donor-acceptor heterojunction, where efficient exciton separation enables chiral acceptor layer to provide differentiated concentration of holes to the channel of organic field-effect transistors. Benefitting from the low defect density at the semiconductor/dielectric interface, the photodetectors exhibit excellent stability, enabling current roll-off of about 3–4% over 500 cycles. The photocurrent dissymmetry value and responsivity for circularly polarized light photodetector in air are 0.24 and 0.28 A W−1, respectively. We further demonstrate circularly polarized light communication based on a real-time circularly polarized light detector by decoding the light signal. As the proof-of-concept, the results hold the promise of large-scale circularly polarized light integrated photonic applications.

Enhancing charge injection from electrodes to the conducting channel and reducing the contact resistance (Rc) are valid strategies not only to improve the performance of organic field-effect transistors (OFETs), but also to enable low-voltage operating devices with a short channel. In order to improve the charge injection efficiency, many efforts have been made to reduce the interfacial injection resistance (Rc,int) in the past few decades, such as by adjusting the metal work function, inserting a buffer layer and so on. However, the method of decreasing the bulk injection resistance (Rc,bulk) in the vertical direction of the semiconductor layer is rarely studied. In this paper, two-dimensional (2D) monolayer and multilayer single-crystal devices of 1,4-bis((5′-hexyl-2,2′-bithiophen-5-yl)ethynyl)benzene (HTEB) were fabricated to study the dependence of the contact resistance of OFETs on crystal thickness. Devices based on monolayer molecular crystals (MMCs), and 4-layer and 15-layer single-crystal devices were found to have Rc of 1.77 kΩ cm, 26.9 kΩ cm and 5.15 MΩ cm, respectively. Thanks to the lower Rc, the MMC devices possess more steady linear mobility at a varied VDS, and a smaller deviation of the linear and saturation mobility. Finally, a low-voltage operating (−2 V) HTEB MMC device was fabricated on a 30 nm HfO2 insulating layer with an ultra-low Rc of 540 Ω cm.

Diketopyrrolopyrrole (DPP) as a building block has been intensively investigated for organic semiconductors and light emitting materials. The synthesis of N-aryl DPPs remains challenging. Herein, we firstly report a new easily handled synthetic method toward N-aryl DPPs through H-DPP with diaryliodonium salt in the presence of CuI, which shows broad reaction scope. Sixteen N-aryl DPPs, including phenyl, furan and thiophene as flanking aromatic groups, were synthesized with yields up to 78 %. These N-aryl DPPs are fluorescent in both solutions and solid states, with quantum yields up to 96 % and 40 %, respectively. Moreover, we show that the reaction between H-DPP and diaryliodonium salt can lead to π-expanded DPPs by using Pd(OAc)2 as catalyst. Nine π-expanded DPPs were obtained in 27-61 % yields. These π-expanded DPPs exhibit good semiconducting properties with hole mobility of 0.71 cm2 V-1 s-1 , demonstrating that they are useful building blocks for high performance organic semiconductors.

Tight coupling between different energy systems makes state analysis of multi-energy integrated systems difficult. From the perspective of data-driven, this paper proposes an anomaly state identification method for power-heat-gas integrated system based on unified power flow model. First, establish a unified power flow model of the power-heat-gas integrated system. Then, using the random matrix theory in big data technology, the historical data and real-time data of the state quantity in the unified power flow model form a random matrix. Finally, the M-P law and the ring law in the random matrix theory are used to qualitatively analyze the system operation. The simulation results verify that the method does not need to identify the physical structure of the system, which provides a new idea for the abnormal state recognition of the power-heat-gas integrated system.

Rigid and planar conjugated molecules have substantial significance due to their potential applications in organic electronics. Herein we report two highly fused ladder type conjugated molecules, TTCTTC and TTTCTTTC, with up to 10 fused rings in which the fused-thiophene rings are fused to the chromeno[6,5,4-def]chromene unit. Both molecules show high HOMO levels and accordingly they can be oxidized into their radical cations with absorptions extending to 1300 nm in the presence of trifluoroacetic acid. Thin films of TTCTTC and TTTCTTTC exhibit p-type semiconductor properties with hole mobilities up to 0.39 cm2 V−1 s−1. Moreover, TTCTTC shows a high fluorescence quantum yield of up to 16.5% in the solid state.

Correction for ‘Fused ambipolar aza-isoindigos with NIR absorption’ by Liping Yao et al., Org. Chem. Front., 2021, DOI: 10.1039/d0qo01495h.

Faced with the tight coupling of multi energy sources, the interaction between different energy supply systems makes it difficult for integrated energy systems (IES) to identify weak nodes. Based on the analysis of the data generated by the actual operation of IES, this paper proposes a weak node identification method based on random matrix theory (RMT). First, establish a unified power flow model for IES. Secondly. introduce RMT and the characteristics of weak nodes, without considering the detailed physical model of the system, using historical data and real-time data to construct the random matrix. Thirdly, the two limit spectrum distribution functions (Marchenko-Pastur law and ring law) are used to qualitatively analyze the system's operating status, calculate linear eigenvalue statistics such as mean spectral radius (MSR), and establish the weak node identification model based on entropy theory. Finally, the simulation of IES verifies the effectiveness of the proposed method and provides a new approach for the identification of weak nodes in IES.

State-of-the-art organic solar cells (OSCs) typically suffer from large voltage loss (V-loss) compared to their inorganic and perovskite counterparts. There are some successful attempts to reduce the V-loss by decreasing the energy offsets between the donor and acceptor materials, and the OSC community has demonstrated efficient systems with either small highest occupied molecular orbital (HOMO) offset or negligible lowest unoccupied molecular orbital (LUMO) offset between donors and acceptors. However, efficient OSCs based on a donor/acceptor system with both small HOMO and LUMO offsets have not been demonstrated simultaneously. In this work, an efficient nonfullerene OSC is reported based on a donor polymer named PffBT2T-TT and a small-molecular acceptor (O-IDTBR), which have identical bandgaps and close energy levels. The Fourier-transform photocurrent spectroscopy external quantum efficiency (FTPS-EQE) spectrum of the blend overlaps with those of neat PffBT2T-TT and O-IDTBR, indicating the small driving forces for both hole and electron transfer. Meanwhile, the OSCs exhibit a high electroluminescence quantum efficiency (EQE(EL)) of approximate to 1 x 10(-4), which leads to a significantly minimized nonradiative V-loss of 0.24 V. Despite the small driving forces and a low V-loss, a maximum EQE of 67% and a high power conversion efficiency of 10.4% can still be achieved. Funding Agencies|National Basic Research Program of China (973 Program) [2013CB834701, 2014CB643501]; Shenzhen Technology and Innovation Commission [JCYJ20170413173814007, JCYJ20170818113905024]; Hong Kong Research Grants Council [T23-407/13 N, N_HKUST623/13, 16305915, 16322416, 606012, 16306117, 16303917]; HK JEBN Limited, HKUST presidents office [FP201]; National Science Foundation of China [21374090]; Swedish Energy Agency Energimyndigheten [2016-010174]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Hong Kong Innovation and Technology Commission [ITC-CNERC14SC01, ITS/083/15]