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Unique Substitution Effect at 5,5′ Positions of a Fused Azobenzene-Boron Complex with N=N Double-Bond π-Conjugated System
摘要： The recent report illustrates superior optical properties, such as near infrared emission, from the polymers with the connection positions at 4,4′ positions in the fused azobenzene–boron complex (BAz). In this study, we initially demonstrate that further narrower band gap can be realized by the substituent effect with bromine groups at 5,5′ positions of BAz than that at 4,4′ positions. From the series of mechanistic studies, perturbation of the energy levels were rationally explained by the contribution difference between the inductive effect and the variable resonance effect which is correlated to the degree of electron distribution of molecular orbitals at the substituent positions. Moreover, it was found that unique electronic states, such as delocalized highest occupied molecular orbital and localized lowest unoccupied molecular orbital, should appear on the main chains of the BAz-containing copolymers with fluorene and bithiophene units according to the optical and electrochemical data and theoretical calculations. Taking advantage of property tunability and the dramatic low LUMO energy level (near ?4.0 eV) of the BAz unit, it can be said that BAz should be a conjugated building block favorable for building advanced optoelectronic devices.
关键词： azobenzene,boron,narrow band gap,conjugated polymer,low LUMO
更新于2025-09-23 15:23:52
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Reconfigurable 2D/0D pa??n Graphene/HgTe Nanocrystal Heterostructure for Infrared Detection
摘要： Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal-to-noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency, and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large-scale graphene electrodes, and a HgTe nanocrystals layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables one to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electron-doped (n) and hole-doped (p) states. We unveil that this functionality enables the design a 2D/0D p?n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that, in this specific configuration, the signal-to-noise ratio for infrared photodetection can be enhanced by 2 orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 109 Jones, whereas the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (<10 μs), which strongly contrasts with the slow response commonly observed for 2D/0D mixed-dimensional heterostructures, where larger photoconduction gains come at the cost of slower response.
关键词： gate-induced diode,infrared detection,narrow band gap nanocrystals,HgTe,graphene
更新于2025-09-23 15:21:01
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Narrowing the Band Gap: The Key to High-Performance Organic Photovoltaics
摘要： Organic photovoltaics (OPVs) have attracted considerable attention in the last two decades to overcome the terawatt energy challenge and serious environmental problems. During their early development, only wide-band-gap organic semiconductors were synthesized and employed as the active layer, mainly utilizing photons in the UV?visible region and yielding power conversion e?ciencies (PCEs) lower than 5%. Afterward, considerable e?orts were made to narrow the polymer donor band gap in order to utilize the infrared photons, which led to the enhancement of the PCE from 5% to 12% in about a decade. Since 2017, the study of narrow-band-gap non-fullerene acceptors helped usher in a new era in OPV research and boosted the achievable the PCE to 17% in only 3 years. In essence, the history of OPV development in the last 15 years can be summarized as an attempt to narrow the band gap of organic semiconductors and better position the energy levels. There are multiple bene?ts of a narrower band gap: (1) considerable infrared photons can be utilized, and as a result, the short-circuit current density can increase signi?cantly; (2) the energy o?set of the lowest unoccupied molecular orbital energy levels or highest occupied molecular orbital energy levels between the donor and acceptor can be reduced, which will reduce the open-circuit voltage loss by minimizing the loss caused by the donor/acceptor charge transfer state; (3) because of the unique molecular orbitals of organic semiconductors, the red-shifted absorption will induce high transmittance in the visible region, which is ideal for the rear subcells in tandem-junction OPVs and transparent OPVs.
关键词： Organic photovoltaics,narrow-band-gap,non-fullerene acceptors,power conversion efficiencies,polymer donors
更新于2025-09-23 15:21:01
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Mechanically Robust All-Polymer Solar Cells from Narrow Band Gap Acceptors with Hetero-Bridging Atoms
摘要： A series of polymer acceptors PF2-DTC, PF2-DTSi, and PF2-DTGe with identical molecular backbone but different central bridging atoms in tricyclic-fused donor units were developed. In all-PSCs, the PF2-DTSi-based blend film exhibited excellent mechanical robustness with an impressively high PCE of up to 10.77%. Moreover, the flexible solar cell based on this blend retained >90% of its initial PCE after bending and relaxing 1,200 times at a bending radius of ~4 mm.
关键词： Mechanical robustness,All-polymer solar cells,Narrow band gap acceptors,Power conversion efficiency,Hetero-bridging atoms
更新于2025-09-23 15:19:57
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High-Performance UVa??Vis Photodetectors Based on a Lead-Free Hybrid Perovskite Crystal (MV)[SbI <sub/>3</sub> Cl <sub/>2</sub> ]
摘要： Low-dimensional lead-free organic?inorganic hybrid perovskites have gained increasing attention as having low toxicity, ease of processing, and good optoelectronic properties. Seeking for lead-free and narrow band gap organic?inorganic hybrid perovskites are of great importance for the development and application of photoelectric materials. Here, we reported a Sb-based organic?inorganic hybrid perovskite (MV)[SbI3Cl2], which has one-dimensional inorganic frameworks of the I-sharing double octahedra. (MV)[SbI3Cl2] shows a narrow direct band gap of 1.5 eV, and displays obvious photoresponse for the 532 nm light with rapid response speed of trise = 0.69 s, tdecay = 0.28 s. With an illumination power of 5 mW and a 50 V bias, the responsivities (R) and external quantum e?ciency (EQE) for (MV)[SbI3Cl2] photodetector under 532 nm laser are 29.75 mA/W and 6.69% respectively. This Sb-based halide double perovskite material will provide an alternative material for photodetector devices.
关键词： organic?inorganic hybrid perovskites,Sb-based,narrow band gap,photodetectors,lead-free
更新于2025-09-23 15:19:57
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Trifluoromethylation Enables a 3D Interpenetrated Low-Band-Gap Acceptor for Efficient Organic Solar Cells
摘要： Herein, tri?uoromethylation has proven to be an effective strategy for ultra-narrow band-gap NFAs. A PCE of 15.59% is achieved from BTIC-CF3-g-based devices, which is the highest value in reported ultra-narrow band-gap acceptors. A ternary device with 16.50% ef?ciency is also obtained, resulting from its red-shifted absorption. Meanwhile, the single-crystal structure of BTIC-CF3-g has been successfully presented, which gives a deep understanding of the solid-state molecular packings in these highly ef?cient acceptors.
关键词： ultra-narrow band-gap,nonfullerene acceptors,tri?uoromethylation,power conversion efficiency,organic solar cells
更新于2025-09-19 17:13:59
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Non-layered ZnSb nanoplates for room temperature infrared polarized photodetectors
摘要： Non-layered 2D ZnSb nanoplates are successfully synthesized by chemical vapor deposition, which possess narrow band gap and novel anisotropic properties. Infrared polarized photodetectors based on the ZnSb nanoplates are designed and exhibit high responsivity, fast photoresponse speed, great stability, high anisotropic conductivity and linear polarization sensitivity.
关键词： anisotropic properties,ZnSb nanoplates,narrow band gap,chemical vapor deposition,infrared polarized photodetectors
更新于2025-09-19 17:13:59
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Direct Z-scheme photocatalytic removal of ammonia via the narrow band gap MoS2/N-doped graphene hybrid catalyst upon near-infrared irradiation
摘要： Near-infrared (NIR) irradiation accounts for approximately 54.3% of the solar spectrum. Therefore, MoS2 and N-doped graphene (NG) were utilised to fabricate a direct Z-scheme NIR-response photocatalytic system (MoS2/NG). The photocatalytic tests showed that MoS2/NG Z-scheme photocatalytic system can result in a 99.6% degradation ratio of ammonia under NIR irradiation, whereas the removal ratio of ammonia was only 64.0% using MoS2 as the photocatalyst under similar conditions. The catalytic e?ciency is still over 90.7% even if the MoS2/NG catalyst was used for ?ve runs, indicating that it is extremely stable. The kinetic research indicated the ?1. The average apparent rate constant kapp for ammonia degradation into N2 was at approximately 0.251 h enhanced photocatalytic activity of MoS2/NG was attributed to the more positive valence band level of the Z-scheme system.
关键词： MoS2/N-doped graphene,Near-infrared irradiation,Degradation ammonia,Narrow band gap,Z-scheme photocatalysis
更新于2025-09-12 10:27:22