Suchergebnisse

Funding: We thank EU horizon 2020 Grant Agreement No. 812872 (TADFlife) for funding. SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430- THF-OLED). ; Commonly, thermally activated delayed fluorescence (TADF) emitters present a twisted donor–acceptor structure. Here, electronic communication is mediated through-bond via π-conjugation between donor and acceptor groups. A second class of TADF emitters are those where electronic communication between donor and acceptor moieties is mediated through-space. In these through-space charge-transfer (TSCT) architectures, the donor and acceptor groups are disposed in a pseudocofacial orientation and linked via a bridging group that is typically an arene (or heteroarene). In most of these systems, there is no direct evidence that the TSCT is the dominant contributor to the communication between the donor and acceptor. Herein we investigate the interplay between through-bond localized excited (LE) and charge-transfer (CT) states and the TSCT in a rationally designed emitter, TPA-ace-TRZ , and a family of model compounds. From our photophysical studies, TSCT TADF in TPA-ace-TRZ is unambiguously confirmed and supported by theoretical modeling. ; Publisher PDF ; Peer reviewed

Antimonene, a novel group 15 two-dimensional material, is functionalized with a tailormade perylene bisimide through strong van der Waals interactions. The functionalization process leads to a significant quenching of the perylene fluorescence, and surpasses that observed for either graphene or black phosphorus, thus allowing straightforward characterization of the flakes by scanning Raman microscopy. Furthermore, scanning photoelectron microscopy studies and theoretical calculations reveal a remarkable charge-transfer behavior, being twice that of black phosphorus. Moreover, the excellent stability under environmental conditions of pristine antimonene has been tackled, thus pointing towards the spontaneous formation of a sub-nanometric oxide passivation layer. DFT calculations revealed that the noncovalent functionalization of antimonene results in a charge-transfer band gap of 1.1 eV ; We thank the ESCA microscopy beamline team at Elettra for technical assistance with the scanning X‐ray photoelectron microscopy measurements. The research leading to these results has received partial funding from the European Union Seventh Framework Programme under grant agreement no. 604391 Graphene Flagship. We thank the Deutsche Forschungsgemeinschaft (DFG‐SFB 953 "Synthetic Carbon Allotropes", Projects A1 and C2), the Interdisciplinary Center for Molecular Materials (ICMM), and the Graduate School Molecular Science (GSMS) for financial support. We thank the MINECO (Spain) for financial support through the "María de Maeztu" Programme for Units of Excellence in R&D (MDM‐2014‐0377) and the projects: MAT2016‐77608‐C3‐1P and 3P, as well as MAT2014‐52477‐C5‐5 and MAT2015‐66888‐C3‐3‐R. Co‐funding from UE is also acknowledged. G.A. thanks the EU for a Marie Curie Fellowship (FP7/2013‐IEF‐627386), and the FAU for the Emerging Talents Initiative (ETI) grant #WS16‐17_Nat_04

Este trabajo se centra en la síntesis de nuevos nanohíbridos dador-aceptor (D/A) de politiofeno solubles en medios acuosos y en la elucidación de la interacción electrónica entre las unidades D/A como en el funcionamiento de los nanohíbridos en forma de películas delgadas en aplicaciones optoelectrónicas. Utilizando técnicas de auto-ensamblaje in-situ de politiofeno en presencia de diferentes nanomateriales como son el óxido de grafeno, puntos cuánticos de semiconductores o láminas de dicalcogenuros de metales de transición se ha conseguido la formación de complejos de transferencia de carga, solubles en agua y con superiores propiedades electrónicas de relevancia para el desarrollo de dispositivos optoelectrónicos basados en películas delgadas

4 páginas, 3 figuras.-- PACS numbers: 71.35.Cc, 61.50.Ks, 71.20.Dg, 78.40.-q ; By first-principles methods we analyze the optical response of transparent dense sodium as a function of applied pressure. We discover an unusual kind of charge-transfer exciton that proceeds from the interstitial distribution of valence electrons. The absorption spectrum is strongly anisotropic, which, just at pressures above the metal-insulator transition, manifests as sodium being optically transparent in one direction but reflective in the other. This result provides key information about the crystal structure of transparent sodium, a new unconventional inorganic electride. ; This work was supported by the Spanish MEC (FIS2007-65702-C02-01), ''Grupos Consolidados UPV/ EHU del Gobierno Vasco'' (IT-319-07), and the European Union through the e-I3 ETSF project (Contract No. 211956). ; Peer reviewed

The game-changing role of graphene oxide (GO) in tuning the excitonic behavior of conjugated polymer nanoparticles is described for the first time. This is demonstrated by using poly(3-hexylthiophene) (P3HT) as a benchmark conjugated polymer and employing an in-situ re-precipitation approach resulting in P3HT nanoparticles (P3HTNPs) with sizes of 50 - 100 nm in intimate contact with GO. During the self-assembly process, GO changes the crystalline packing of P3HT chains in the forming P3HTNPs from H to H/J aggregates exhibiting exciton coupling constants as low as 2 meV, indicating favorable charge separation along the P3HT chains. Concomitantly, π-π interface interactions between the P3HTNPs and GO sheets are established resulting in the creation of P3HTNPs-GO charge-transfer complexes whose energy bandgaps are lowered by up to 0.5 eV. Moreover, their optoelectronic properties, pre-established in the liquid phase, are retained when processed into thin films from the stable aqueous dispersions, thus eliminating the critical dependency on external processing parameters. These results can be transferred to other types of conjugated polymers. Combined with the possibility of employing water based "green" processing technologies, charge-transfer complexes of conjugated polymer nanoparticles and GO open new pathways for the fabrication of improved optoelectronic thin film devices. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 642742. AMB, and WKM acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R) and the Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds). ; Peer reviewed

1 Figure.-- Abstract of the work presented at "Current Trends in Electrochemistry", 41st Meeting of the Electrochemisty Group of the Spanish Royal Society of Chemistry, 1st French‐Spanish Atelier/Workshop on Electrochemistry, 6 - 9 July 2021, Paris (France). ; Photoelectrochemical techniques are accurate for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers, carbon nanomaterials (GO, CNTs, CDs) or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, electronics, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of nanoscience and nanotechnology. ; MINECO and AEI/FEDER/UE (project ENE2016-79282-C5-1-R), European Union (H2020-MSCAITN- 2014-ETN 642742), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER/UE). ; Peer reviewed

Nanoscale charge control is a key enabling technology in plasmonics, electronic band structure engineering, and the topology of two-dimensional materials. By exploiting the large electron affinity of α-RuCl3, we are able to visualize and quantify massive charge transfer at graphene/α-RuCl3 interfaces through generation of charge-transfer plasmon polaritons (CPPs). We performed nanoimaging experiments on graphene/α-RuCl3 at both ambient and cryogenic temperatures and discovered robust plasmonic features in otherwise ungated and undoped structures. The CPP wavelength evaluated through several distinct imaging modalities offers a high-fidelity measure of the Fermi energy of the graphene layer: EF = 0.6 eV (n = 2.7 × 1013 cm–2). Our first-principles calculations link the plasmonic response to the work function difference between graphene and α-RuCl3 giving rise to CPPs. Our results provide a novel general strategy for generating nanometer-scale plasmonic interfaces without resorting to external contacts or chemical doping. ; Research at Columbia was supported as part of the Energy Frontier Research Center on Programmable Quantum Materials funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award No. DE-SC0019443. J.Z., L.X., and A.R. were supported by the European Research Council (ERC-2015-AdG694097), the Cluster of Excellence "Advanced Imaging of Matter" (AIM) EXC 2056 - 390715994, funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under RTG 2247, Grupos Consolidados (IT1249-19) and SFB925 "Light induced dynamics and control of correlated quantum systems". J.Z. acknowledges funding received from the European Union Horizon 2020 research and innovation program under Marie Sklodowska-Curie Grant Agreement 886291 (PeSD-NeSL). J.Z., L.X., and A.R. would like to acknowledge Nicolas Tancogne-Dejean for fruitful discussions and also acknowledge support by the Max Planck Institute-New York City Center for Non-Equilibrium Quantum Phenomena. The Flatiron Institute is a division of the Simons Foundation. D.G.M. acknowledges support from the Gordon and Betty Moore Foundation's EPiQS Initiative, Grant GBMF9069. Work at ORNL was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant JPMXP0112101001, JSPS KAKENHI Grant JP20H00354, and the CREST (JPMJCR15F3), JST. S.E.N. was supported by the Division of Scientific User Facilities of the U.S. DOE Basic Energy Sciences. M.M.F. acknowledges support from the Office of Naval Research Grant N00014-18-1-2722. D.N.B. is the Vannevar Bush Faculty ONR-VB: N00014-19-1-2630 and Moore investigator in Quantum Materials EPIQS program #9455. A.S.M acknowledges support from award 80NSSC19K1210 under the NASA Laboratory Analysis of Returned Samples program. ; Peer reviewed

We demonstrate that efficient and nearly field-independent charge separation of electron hole pairs in organic planar heterojunction solar cells can be described by an incoherent hopping mechanism. Using kinetic Monte Carlo simulations that include the effect of on-chain delocalization as well as entropic contributions, we simulate the dissociation of the charge-transfer state in polymer fullerene bilayer solar cells. The model further explains experimental results of almost field independent charge separation in bilayers of molecular systems with fullerenes and provides important guidelines at the molecular level for maximizing the efficiencies of organic solar cells. Thus, utilizing coherent phenomena is not necessarily required for highly efficient charge separation in organic solar cells. ; This project has received funding from the Universidad Carlos III de Madrid, the European Union's Seventh Framework Programme for research, technological development, and demonstration under Grant Agreement No. 600371, el Ministerio de Economı́a, Industria y Competitividad (COFUND2014-51509), el Ministerio de Educación, cultura y Deporte (CEI-15-17), and Banco Santander. We also acknowledge additional funding from the German Research Foundation DFG (GRK1640) and the Bavarian University Centre for Latin America (BAYLAT).

Pentacene molecules have recently been observed to form a well-ordered monolayer on the (110) surface of rutile TiO, with the molecules adsorbed lying flat, head to tail. With the geometry favorable for direct optical excitation and given its ordered character, this interface seems to provide an intriguing model to study charge-transfer excitations where the optically excited electrons and holes reside on different sides of the organic-inorganic interface. In this work, we theoretically investigate the structural and electronic properties of this system by means of ab initio calculations and compute its excitonic absorption spectrum. Molecular states appear in the band gap of the clean TiO surface, which enables charge-transfer excitations directly from the molecular HOMO to the TiO conduction band. The calculated optical spectrum shows a strong polarization dependence and displays excitonic resonances corresponding to the charge-transfer states, which could stimulate new experimental work on the optical response of this interface. ; This work was financed by the Deutsche Forschungsgemeinschaft (DFG) through the SFB 1083 project. MPL, DSP and PK also acknowledges support from Spanish MINECO (Grants No. MAT2013-46593-C6-2-P and MAT2016-78293-C6-4-R) and PK also acknowledges financial support from Fellows Guipuzcoa program from Gipuzkoako Foru Aldundia through the FEDER funding scheme of the European Union. ; Peer Reviewed

Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection. ; S.F. acknowledges fellowship support from Chinese Scholarship Council (CSC). X.J. acknowledges financial support by DFG through the Excellence Initiative by the Graduate School of Excellence Materials Science in Mainz (MAINZ) (GSC 266) and support from the Max Planck Graduate Center mit der Johannes Gutenberg-Universität Mainz (MPGC). A.J.H. acknowledges support from the European Research Council Horizon 2020 ERC grant no. 678004 (Doping on Demand). ICN2 was supported by the Severo Ochoa program from Spanish MINECO (grant no. SEV-2017-0706). K.-J.T. acknowledges funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 804349 (ERC StG CUHL) and financial support through the MAINZ Visiting Professorship.

Graphene quantum dots (GQD) are interesting materials due to the confined sizes which allow to exploit their optoelectronic properties, especially when they interface with organic molecules through physisorption. In particular, when interfaces are formed, charge transfer (CT) processes can occur, in which electrons can flow either from the GQD to the absorbed molecule, or vice versa. These processes are accessible by modeling and computational analysis. Yet, the presence of different environments can strongly affect the outcome of such simulations which, in turn, can lead to wrong results if not taken into account. In this multiscale study, we assess the sensibility of the computational approach and compute the CT, calculated at interfaces composed by GQD and amino-acene derivatives. The hole transfer is strongly affected by dynamic disorder and the nature of the environment, and imposes stringent descriptions of the modeled systems to ensure enhanced accuracy of the transfer of charges. ; Narodowe Centrum Nauki, Grant/Award Number: UMO-2015/19/P/ST4/03636; University of Warsaw, Grant/Award Number: G53-8; Swedish Infrastructure Committee, Grant/Award Numbers: 1-465,, 1-415, 1-87; European Union's Horizon 2020; National Science Centre, Poland, Grant/Award Number: UMO-2015/19/P/ST4/03636

1 figure.-- Talk delivered at the HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual in Benasque (Aragon, Spain). ; Photoelectrochemistry is a valuable technique for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors and carbon nanomaterials (GO, CNTs), unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of carbon nanoscience and nanotechnology. ; MINEICO (project ENE2016-79282-C5-1-R, AEI/FEDER, UE), European Union (H2020-MSCA-ITN-2014-ETN 642742 ), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER, UE).