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Cheol-Joon Park, Hyeon Jung Park, Jae Yoon Lee, Jeongyong Kim, Chul-Ho Lee, Jinsoo Joo
A several-layer n-type MoS2 was partially hybridized with an organic crystalline p-type rubrene nanosheet through van der Waals interactions to fabricate a two-dimensional lateral-type n-p hetero-junction optoelectronic device. The field-effect-transistors (FET) using lateral-type MoS2 /rubrene hybrids exhibited both gate-tunable diode and anti-ambipolar transistor characteristics. The FET devices show the coexistence of n-type, p-type states, and off-states controlled by the gate bias. From the photocurrent mapping experiments, the gate-bias-dependent photovoltaic effect was observed from the hetero-junction regions of the MoS2 /rubrene FETs...
August 9, 2018: ACS Applied Materials & Interfaces
Xinglong Ren, C Daniel Frisbie, Chris Leighton
Although electrolyte gating has been demonstrated to enable control of electronic phase transitions in many materials, long sought-after gate-induced insulator-metal transitions in organic semiconductors remain elusive. To better understand limiting factors in this regard, here we report detailed wide-range resistance-temperature (R-T) measurements at multiple gate voltages on ionic-liquid-gated rubrene single crystals. Focusing on the previously observed high bias regime where conductance anomalously decreases with increasing bias magnitude, two surprising (and related) features are uncovered...
August 1, 2018: Journal of Physical Chemistry Letters
Jae Joon Kim, Stefan Bachevillier, D Leonardo Gonzalez Arellano, Benjamin P Cherniawski, Edmund K Burnett, Natalie Stingelin, Cédric Ayela, Özlem Usluer, Stefan C B Mannsfeld, Guillaume Wantz, Alejandro L Briseno
The relationship between charge transport and surface morphology is investigated by utilizing rubrene single crystals of varying thicknesses. In the case of pristine crystals, the surface conductivities decrease exponentially as the crystal thickness increases until ∼4 μm, beyond which the surface conductivity saturates. Investigation of the surface morphology using optical and atomic force microscopy reveals that thicker crystals have a higher number of molecular steps, increasing the overall surface roughness compared with thin crystals...
July 30, 2018: ACS Applied Materials & Interfaces
Ryo Nagata, Hajime Nakanotani, William J Potscavage, Chihaya Adachi
Harvesting of both triplets and singlets yields electroluminescence quantum efficiencies of nearly 100% in organic light-emitting diodes (OLEDs), but the production efficiency of excitons that can undergo radiative decay is theoretically limited to 100% of the electron-hole pairs. Here, breaking of this limit by exploiting singlet fission in an OLED is reported. Based on the dependence of electroluminescence intensity on an applied magnetic field, it is confirmed that triplets produced by singlet fission in a rubrene host matrix are emitted as near-infrared (NIR) electroluminescence by erbium(III) tris(8-hydroxyquinoline) (ErQ3 ) after excitonic energy transfer from the "dark" triplet state of rubrene to an "emissive" state of ErQ3 , leading to NIR electroluminescence with an overall exciton production efficiency of 100...
July 5, 2018: Advanced Materials
T Mukherjee, Sumona Sinha, M Mukherjee
X-ray absorption spectra (XAS), the density of states (DOS) and the electron density distribution of the HOMO and LUMO for flat and twisted rubrene molecules have been calculated using density functional theory (DFT). The simulated XAS spectra are validated by experimental C K-edge near-edge X-ray absorption fine structure (NEXAFS) data. We demonstrate that the NEXAFS spectra of rubrene thin films of different thicknesses can be explained in terms of different combinations of spectral intensity from the twisted and the flat randomly oriented molecules...
July 11, 2018: Physical Chemistry Chemical Physics: PCCP
Dong Wei, Fusheng Ma, Rui Wang, Shangyi Dou, Peng Cui, Hao Huang, Jun Ji, Endong Jia, Xiaojie Jia, Sajid Sajid, Ahmed Mourtada Elseman, Lihua Chu, Yingfeng Li, Bing Jiang, Juan Qiao, Yongbo Yuan, Meicheng Li
Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices...
June 25, 2018: Advanced Materials
Takashi Yamada, Mariko Kinoshita, Kento Araragi, Yu Watanabe, Takahiro Ueba, Hiroyuki S Kato, Toshiaki Munakata
Spectroscopic and nanoscale imaging investigations concerning the spatial extent of molecular orbitals at organic/substrate interfaces have been of intense interest to understand charge dynamics. Here, the spatial extent of unoccupied molecular orbitals of ultrathin rubrene [5,6,11,12-tetraphenyltetracene] films has been investigated with scanning tunneling microscopy and spectroscopy. Based on constant-current distance (z)-voltage (V) measurements, the unoccupied energy levels are elucidated and found to be consistent with previously reported macroscopic two-photon photoemission (2PPE) spectroscopy...
June 27, 2018: Physical Chemistry Chemical Physics: PCCP
Lu Zhang, Kok Wai Cheah
Thermally activated delayed florescence (TADF) materials can be an efficient host in organic LED (OLED). It is because it is possible to couple energetically the emission energy level of a dopant to the energy levels in the TADF material. In this work fluorescent emitters 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5 H,11H-10-(2-benzothiazolyl)quinolizino-9,9a,1gh coumarin (c545t) and 5,6,11,12-tetraphenyltetracene (rubrene) were used as dopants in a blended TADF host; tris(4-carbazoyl-9-ylphenyl)amine (TCTA) with 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine (Tm3PyBPZ)...
June 11, 2018: Scientific Reports
Gaozhan Xie, Sebastian Hahn, Frank Rominger, Jan Freudenberg, Uwe H F Bunz
The synthesis, properties and solid state X-ray single crystal structures of two new rubrene-derivatives, viz diazarubrene (4,4'-(6,12-diphenyltetracene-5,11-diyl)dipyridine) and tetraazarubrene (5,6,11,12-tetra(pyridin-4-yl)tetracene), are reported. Both the azarubrenes are more oxidatively stable than rubrene itself and show very similar optical properties but differ in their crystal packing from that of rubrene.
July 5, 2018: Chemical Communications: Chem Comm
Xiaoyu Xie, Alejandro Santana-Bonilla, Alessandro Troisi
A substantial amount of evidence indicates a relevant role played by the nonlocal electron-phonon couplings in the mechanism of charge transport in organic semiconductors. In this work, we compute the nonlocal electron-phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained from ab initio methods. We do not make the rigid molecular approximation allowing a mixing of intra- and intermolecular modes, and we use a supercell approach to sample the momentum space...
July 10, 2018: Journal of Chemical Theory and Computation
Yuanyuan Hu, Lang Jiang, Qinjun Chen, Jing Guo, Zhuojun Chen
It is commonly accepted that gate dielectric dipoles can induce energetic disorder in organic field-effect transistors. However, convincing experimental evidence that directly demonstrate this effect are still in lack. In this work, we present a combined experimental and theoretical study to reveal this effect. We have investigated the temperature-dependent mobility of two rubrene single-crystal transistors with different polymer dielectrics. Model fittings of the data indicate there is higher energetic disorder in the device on dielectric with larger permittivity...
June 7, 2018: Journal of Physical Chemistry Letters
Yasuyuki Yokota, Hiroo Miyamoto, Akihito Imanishi, Jun Takeya, Kouji Inagaki, Yoshitada Morikawa, Ken-Ichi Fukui
Electric double-layer transistors based on ionic liquid/organic semiconductor interfaces have been extensively studied during the past decade because of their high carrier densities at low operation voltages. Microscopic structures and the dynamics of ionic liquids likely determine the device performance; however, knowledge of these is limited by a lack of appropriate experimental tools. In this study, we investigated ionic liquid/organic semiconductor interfaces using molecular dynamics to reveal the microscopic properties of ionic liquids...
May 9, 2018: Physical Chemistry Chemical Physics: PCCP
Yujeong Lee, Kang Lib Kim, Han Sol Kang, Beomjin Jeong, Chanho Park, Insung Bae, Seok Ju Kang, Youn Jung Park, Cheolmin Park
Epitaxial crystallization of thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films is important for the full utilization of their ferroelectric properties. Epitaxy can offer a route for maximizing the degree of crystallinity with the effective orientation of the crystals with respect to the electric field. Despite various approaches for the epitaxial control of the crystalline structure of PVDF-TrFE, its epitaxy on a semiconductor is yet to be accomplished. Herein, the epitaxial growth of PVDF-TrFE crystals on a single-crystalline organic semiconductor rubrene grown via physical vapor deposition is presented...
May 2018: Small
Aditi R Naik, Jae Joon Kim, Özlem Usluer, D Leonardo Gonzalez Arellano, Ethan B Secor, Antonio Facchetti, Mark C Hersam, Alejandro L Briseno, James J Watkins
Scalable fabrication of high-resolution electrodes and interconnects is necessary to enable advanced, high-performance, printed, and flexible electronics. Here, we demonstrate the direct printing of graphene patterns with feature widths from 300 μm to ∼310 nm by liquid-bridge-mediated nanotransfer molding. This solution-based technique enables residue-free printing of graphene patterns on a variety of substrates with surface energies between ∼43 and 73 mN m-1 . Using printed graphene source and drain electrodes, high-performance organic field-effect transistors (OFETs) are fabricated with single-crystal rubrene (p-type) and fluorocarbon-substituted dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDIF-CN2 ) (n-type) semiconductors...
May 9, 2018: ACS Applied Materials & Interfaces
Lea Nienhaus, Mengfei Wu, Vladimir Bulović, Marc A Baldo, Moungi G Bawendi
The process of upconversion leads to emission of photons higher in energy than the incident photons. Near-infrared-to-visible upconversion, in particular, shows promise in sub-bandgap sensitization of silicon and other optoelectronic materials, resulting in potential applications ranging from photovoltaics that exceed the Shockley-Queisser limit to infrared imaging. A feasible mechanism for near-infrared-to-visible upconversion is triplet-triplet annihilation (TTA) sensitized by colloidal nanocrystals (NCs)...
July 3, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Malte Fugel, Dylan Jayatilaka, Emanuel Hupf, Jacob Overgaard, Venkatesha R Hathwar, Piero Macchi, Michael J Turner, Judith A K Howard, Oleg V Dolomanov, Horst Puschmann, Bo B Iversen, Hans-Beat Bürgi, Simon Grabowsky
Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element-hydrogen distances, r ( X -H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r ( X -H) values obtained from HAR...
January 1, 2018: IUCrJ
Alessandro Landi, Raffaele Borrelli, Amedeo Capobianco, Amalia Velardo, Andrea Peluso
Second-order cumulant expansion of the time dependent reduced density matrix has been employed to evaluate hole hopping rates in pentacene, tetracene, picene, and rubrene homodimers. The cumulant expansion is a full quantum mechanical approach, which enables the use of the whole set of nuclear coordinates in computations and the inclusion of both the effects of the equilibrium position displacements and of normal mode mixing upon hole transfer. The time dependent populations predicted by cumulant approach are in good agreement with those obtained by numerical solution of time dependent Schrödinger equation, even for ultrafast processes, where the Fermi Golden Rule fails...
March 13, 2018: Journal of Chemical Theory and Computation
Yi-Sheng Lai, Fei Pan, Yen-Hsun Su
A firefly-like chemiluminescence reaction was utilized in a ZrO2 nanoparticle matrix of water splitting cells, where the chlorophyll of Lantana camara was used as the major photosensitizer to excite electrons to the conduction band of ZrO2 . The fluorescence resonance energy transfer (FRET) was induced by rubrene, a firefly-like chemiluminescence molecule, and Lantana camara chlorophyll combined with 9,10-diphenylanthracene. The ZrO2 nanoparticle film coated by the chlorophyll of Lantana camara and 9,10-diphenylanthracene under chemiluminescence irradiation in 1 M KHCO3 water solution demonstrated the highest photocurrent density (88...
February 7, 2018: ACS Applied Materials & Interfaces
Xiantong Tang, Yeqian Hu, Weiyao Jia, Ruiheng Pan, Junquan Deng, Jinqiu Deng, Zhenghong He, Zuhong Xiong
Singlet fission is usually the only reaction channel for excited states in rubrene-based organic light-emitting diodes (OLEDs) at ambient temperature. Intriguingly, we discover that triplet fusion (TF) and intersystem crossing (ISC) within rubrene-based devices begin at moderate and high current densities (j), respectively. Both processes enhance with decreasing temperature. This behavior is discovered by analyzing the magneto-electroluminescence curves of the devices. The j-dependent magneto-conductance, measured at ambient temperature indicates that spin mixing within polaron pairs that are generated by triplet-charge annihilation (TQA) causes the occurrence of ISC, while the high concentrations of triplets are responsible for generating TF...
January 17, 2018: ACS Applied Materials & Interfaces
Lili Bao, Yan Zou, Allison Kirk, Michael D Heagy
This report investigates the excited-state properties of a series of N-aryl-2,3-naphthalimides along with their fabrication into OLEDs and electroluminescence measurements. The N-aryl-2,3-NIs substituted specifically with chloro, fluoro, and methoxy substituents were chosen because of their unique propensity to display two emission bands or panchromatic fluorescence. Using the Lippert-Mataga analysis along with TD-DFT calculations, the excited states were determined to be n,π* and π,π*. The TD-DFT calculations on the geometries of the excited states indicate that the excited state shows a planar structure...
December 28, 2017: Journal of Physical Chemistry. A
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