139 research outputs found
Impact of donor halogenation on reorganization energies and voltage losses in bulk-heterojunction solar cells
No full textDonor halogenation is a common molecular design strategy used to reduce voltage losses (ΔVloss) and improve the power conversion efficiency (PCE) of bulk-heterojunction (BHJ) organic solar cells. Here, the impact of donor halogenation on the performance of organic donor–acceptor (DA) solar cells based on over 30 different materials systems is investigated, and the main reason for the improved performance of solar cells after donor halogenation is ascribed to the increased energy of the charge transfer (CT) state, and the reduced reorganization energy of the CT states (λCT). Also, the impact of donor halogenation on λCT is found to be stronger for the solar cells using the Y-series acceptors (Y5, Y6, etc.) than those using the non-Y-series acceptors (fullerene, ITIC, etc.), which is conducive to achieving lower ΔVloss in organic solar cells. Finally, the impact of donor halogenation on the solar cell performance is demonstrated to be dependent on the halogen substitution position, as well as the number of halogen atoms added to the donor molecule: Halogen substitution on the side groups of the donor molecule is found to be more effective than substitution at the backbone in reducing ΔVloss. These results suggest that future molecular design strategies focusing on the reduction of materials reorganization energy will be of great importance for further improving the performance of organic solar cells
Goniozus omanensis (Hymenoptera: Bethylidae) an important parasitoid of the lesser date moth Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae) in Oman
No full textA new species of bethylid parasitoid wasp, Goniozus omanensis Polaszek sp. n., is described based on morphology and DNA sequence data. The species is currently known only from the lesser date moth Batrachedra amydraula, a pest of economic importance, but can be reared on two factitious host species. G. omanensis is compared with G. swirskiana, known from the same host in Israel. We summarise current knowledge of G. omanensis life-history, and its potential as an agent of biological pest control.Copyright: © 2019 Polaszek et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article.NHM Repositor
Atomically dispersed tungsten on metal halide monolayer as a ferromagnetic Chern insulator
No full textAlthough the quantum anomalous Hall (QAH) effect has been experimentally observed in several magnetically doped topological insulators, up to now, it only survives at a very low temperature. More suitable candidate QAH insulators that can work at high temperature are much desired. Here, we propose an experimentally feasible way to realize a robust QAH insulator: atomically dispersed transition metals (e.g., W) on a two-dimensional porous metal halide normal insulator (e.g., InI₃), which has been developed as a state-of-the-art chemical technology broadly adopted for homogeneous catalysis. Based on the first-principles calculations, we predict that the atomic W embedded in an InI₃ monolayer forms an intrinsic ferromagnetic QAH insulator, which exhibits robust uniform out-of-plane ferromagnetic order up to ∼160K and a topologically nontrivial band gap of 56 meV with a nonzero Chern number (|C|=2). We also study its magneto-optical Kerr effect and collective plasma excitation modes, which may help for further experimental verifications and measurement of interesting physical features of Dirac-like electronic dispersion. Our results introduce a feasible method to obtain the QAH effect, which may motivate intensive experimental interest in this field
Data related to "Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers", Nature Communications (2020), DOI 10.1038/s41467-020-14549-w
No full textOrganic photovoltaics based on non-fullerene acceptors (NFAs) show record efficiency of 16 to 17% and increased photovoltage owing to the low driving force for interfacial charge- transfer. However, the low driving force potentially slows down charge generation, leading to a tradeoff between voltage and current. Here, we disentangle the intrinsic charge-transfer rates from morphology-dependent exciton diffusion for a series of polymer:NFA systems. Moreover, we establish the influence of the interfacial energetics on the electron and hole transfer rates separately. We demonstrate that charge-transfer timescales remain at a few hundred femtoseconds even at near-zero driving force, which is consistent with the rates predicted by Marcus theory in the normal region, at moderate electronic coupling and at low re-organization energy. Thus, in the design of highly efficient devices, the energy offset at the donor:acceptor interface can be minimized without jeopardizing the charge-transfer rate and without concerns about a current-voltage tradeoff
Low band gap polymers for photovoltaic device with photocurrent response wavelengths over 1000nm
No full textAbstractTo pursue high power conversion efficiency (PCE) of polymer solar cells (PSCs), many new semiconducting polymers with low band gaps have been developed in the past several years. In this perspective paper, we focused on super low band gap photovoltaic polymers with photocurrent response extending over 1000nm. This kind of micrometer-response polymers (μmR-polymer) could increase the short circuit current (JSC) due to better match of absorption spectra of the polymers with the solar irradiation and show tremendous potential for application in tandem solar cells and transparent solar cells. The necessary conditions for the design of this kind of μmR-polymers are discussed. Furthermore, the remaining problems and challenges, and the key research direction in near future are discussed
Tunable Single-Atom Catalysis of CO Oxidation on a Transition Metal-Anchored Defective In<sub>2</sub>Se<sub>3</sub> Monolayer
No full textSingle-atom catalysts (SACs) have attracted extensive
attention
owing to their high atom efficiency and catalytic activity. However,
their superior catalytic properties can hardly be manipulated without
a suitable substrate. Here, based on first-principles calculations,
we demonstrated that a two-dimensional (2D) defective In2Se3 monolayer with Se vacancy could be used as a proper
substrate for various single atoms of transition metals including
Zn, Rh, Ru, Pd, Ag, Ir, Pt, and Au. Moreover, the energy barrier of
the rate-determining step can be effectively regulated by polarization
switching of monolayer In2Se3, which is much
lower in M|VSe-In2Se3 (M = Pt, Pd,
Ag, and Au) with upward polarization. Especially, Ag|VSe-In2Se3 with upward polarization is identified
as a highly efficient catalyst for CO oxidation due to the fairly
low energy barrier (0.547 eV)
Indacenodithieno[3,2‑<i>b</i>]thiophene-Based Wide Bandgap D‑π‑A Copolymer for Nonfullerene Organic Solar Cells
No full textHerein, a wide-bandgap (2.02 eV) donor-π-acceptor
(D-π-A) polymer PIDTT-DTffBTA, composed of a rigid indacenodithieno[3,2-b]thiophene (IDTT) and fluorinated benzo[d][1,2,3]triazole (ffBTA) units as D and A units, respectively, is
synthesized. In comparison with its analogue benzodithiophene-alt-benzotriazole copolymer J52 with classic benzodithiophene
(BDT) as the D unit, PIDTT-DTffBTA demonstrates a lower-lying HOMO
energy level and higher carrier mobilities when paired with a nonfullerene
acceptor (NFA) Y6 based on a ladder-type dithienothiophen[3.2-b]-pyrrolobenzothiadiazole central unit. Thus, PIDTT-DTffBTA:Y6
based organic solar cells (OSCs) exhibit an improved power conversion
efficiency (PCE) of 11.05% than that of J52:Y6 (7.15%), which is also
the highest value for IDTT-based photovoltaic polymers. This result
proves that the IDTT unit is also a promising building block to construct
not only NFAs but also p-type photovoltaic polymers
Synthesis and properties of polythiophenes with conjugated side‐chains containing carbon–carbon double and triple bonds
No full textSynthesis and Photovoltaic Properties of Donor−Acceptor Copolymers Based on 5,8-Dithien-2-yl-2,3-diphenylquinoxaline
No full textThe effect of conjugated π-bridge and fluorination on the properties of asymmetric-building-block-containing polymers (ABC polymers) based on dithienopyran donor and benzothiadiazole acceptors
No full textInserting a hexylthiophene bridge between DTPa and BTs significantly reduced the intramolecular charge transfer and consequently affected the properties of the resulting ABC polymers.</p
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