摘要 :
A new electrontransport polymer, poly{[N,N'-dioctylperylene-3,4,9,10-bis(dicarb-oximide)-1 ,7(6)-diyl]-o/t-[(2,5-bis(2-ethyl-hexyl)-1 ,4-phenylene)bis(ethyn-2,1 -diyl]} (PDIC8-EB), is synthesized. In chloroform, the polymer underg...
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A new electrontransport polymer, poly{[N,N'-dioctylperylene-3,4,9,10-bis(dicarb-oximide)-1 ,7(6)-diyl]-o/t-[(2,5-bis(2-ethyl-hexyl)-1 ,4-phenylene)bis(ethyn-2,1 -diyl]} (PDIC8-EB), is synthesized. In chloroform, the polymer undergoes self-assembly, forming a nanowire suspension. The nanowire's optical and electrochemical properties, morphological structure, and field-effect transistor (FET) characteristics are investigated. Thin films fabricated from a PDIC8-EB nanowire suspension are composed of ordered nanowires and ordered and amorphous non-nanowire phases, whereas films prepared from a homogeneous PDIC8-EB solution consist of only the ordered and amorphous non-nanowire phases. X-ray scattering experiments suggest that in both nanowires and ordered phases, the PDIC8 units are laterally stacked in an edge-on manner with respect to the film plane, with full interdigitation of the octyl chains, and with the polymer backbones preferentially oriented within the film plane. The ordering and orientations are significantly enhanced through thermal annealing at 200 °C under inert conditions. The polymer film with high degree of structural ordering and strong orientation yields a high electron mobility (0.10 + 0.05 cm~2 V~(-1) s~(-1)), with a high on/off ratio (3.7 × 106), a low threshold voltage (8 V), and negligible hysteresis (0.5 V). This study demonstrates that the polymer in the nanowire suspension provides a suitable material for fabricating the active layers of high-performance n-channel FET devices via a solution coating process.
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Persistent emission with a long lifetime (＞1 s) from organic materials can only be observed at a low temperature, because of the significant nonradia-tive deactivation pathway that occurs at room-temperature (RT). If organic mate...
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Persistent emission with a long lifetime (＞1 s) from organic materials can only be observed at a low temperature, because of the significant nonradia-tive deactivation pathway that occurs at room-temperature (RT). If organic materials with persistent RT emission in air could be developed, they could potentially be utilized for a variety of applications. Here, organic host-guest materials with efficient persistent RT phosphorescence (RTP) are developed by minimizing the nonradiative deactivation pathway of triplet excitons. The nonradiative deactivation pathway is dependent on both nonradiative deactivation of the guest and quenching by diffusional motion of the host. The rigidity and oxygen barrier properties of the steroidal compound used as the host suppressed the quenching, and the aromatic hydrocarbon used as the guest is highly deuterated to minimize nonradiative deactivation of the guest. Red-green-blue persistent RTP with a lifetime ＞1 s and a quantum yield ＞10% in air is realized for a pure organic material.
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The electronic structure of donor/acceptor polyenes(merocyanines) is studied by means of electroabsorption (Stark) spectroscopy. Molecules belonging to this class exhibit an extreme variability of their and nonlinear optical prope...
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The electronic structure of donor/acceptor polyenes(merocyanines) is studied by means of electroabsorption (Stark) spectroscopy. Molecules belonging to this class exhibit an extreme variability of their and nonlinear optical properties. Depending on the nature of the donor and acceptor end groups and the polarity of their solvent environment they can adopt ground state molecular structures between limits with mostly localized double bonds (polyene-like) or fully delocalized double bonds(cyanine-like).
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We report on the photovoltaic properties of organic solar cells based on pentacene and C_(60) thin films with a focus on their spectral responses and the effect of thermal annealing. Spectra of external quantum efficiency (EQE) ar...
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We report on the photovoltaic properties of organic solar cells based on pentacene and C_(60) thin films with a focus on their spectral responses and the effect of thermal annealing. Spectra of external quantum efficiency (EQE) are measured and analyzed with a one dimensional exciton diffusion model dependent upon the complex optical functions of pentacene films, which are measured by spectro scopic ellipsometry. An improvement in EQE is observed when the thickness of the bathocuproine (BCP) layer is decreased from 12 nm to 6 nm. Detailed analysis of the EQE spectra indicates that large exciton diffusion lengths in the pentacene films are responsible for the overall high EQE values near wavelengths of 668 nm. Analysis also shows that improvement in the EQE of devices with the thinner BCP layer can be attributed to a net gain in optical field distribution and improvement in carrier collection efficiency. An improvement in open-circuit voltage (V_(OC)) is also achieved through a thermal annealing process, leading to a net increase in power conversion efficiency. Integration of the EQE spectrum with an AM 1.5 G spectrum yields a predicted power conversion efficiency of 1.8 ± 0.2%. The increase in V_(OC) is attributed to a significant reduction in the diode reverse saturation current upon annealing.
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摘要 :
Siloles are attractive building blocks for the design and synthesis of organic semiconductors that exhibit potential applications in light-emitting diodes, solar cells, field-effect transistors, and sensors. Understanding how mole...
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Siloles are attractive building blocks for the design and synthesis of organic semiconductors that exhibit potential applications in light-emitting diodes, solar cells, field-effect transistors, and sensors. Understanding how molecular engineering of the electronic structures can help control the properties of these materials has attracted significant research effort. In the present review we illustrate the current state-of-the-art of the molecular engineering of siloles, especially focusing on the effects of substituents and on the electronic structure of siloles.
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摘要 :
Layer-by-layer growth of the electron-transport material tris{2,5-bis(3,5-bis-trifluoromethyl-phenyl)-thieno} [3,4-b,h,n]-l,4,5,8,9,12-hexaazatriphenylene (THAP) on Au(111) is probed by scanning tunneling microscopy (STM). A relat...
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Layer-by-layer growth of the electron-transport material tris{2,5-bis(3,5-bis-trifluoromethyl-phenyl)-thieno} [3,4-b,h,n]-l,4,5,8,9,12-hexaazatriphenylene (THAP) on Au(111) is probed by scanning tunneling microscopy (STM). A relative of discotic liquid crystalline molecules, THAP is shown to grow in commensurate ordered planes from the first to fourth monolayers. The four monolayers all show a concordant ordered structure in which the molecules arrange parallel to the substrate in a hexagonal close-packed lattice with a herringbone pattern defined by alternating rows of molecules with antiparallel orientation. The unit cell is rectangular with two molecules per cell and is nearly equivalent for each layer. The spatial broadening of the local density of states due to the metallic substrate is appreciably diminished in upper layers, as expected and as evidenced by the localization of states seen in STM. There is good agreement between the highest occupied molecular orbital obtained in density functional theory calculations for a single molecule and STM images of the upper layers, in accord with the localized nature of electronic states on molecules under minimal substrate influence.
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摘要 :
This work focuses on organic-organic heterojunctions (OOHs) formed between two small-molecule, low band-gap, semiconductors, tris{2,5-bis(3,5-bis-trifluoromethyl-phenyl)-thieno}[3,4-b,h,n]-l ,4,5,8,9,12 -hexaaza-triphenylene (THAP...
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This work focuses on organic-organic heterojunctions (OOHs) formed between two small-molecule, low band-gap, semiconductors, tris{2,5-bis(3,5-bis-trifluoromethyl-phenyl)-thieno}[3,4-b,h,n]-l ,4,5,8,9,12 -hexaaza-triphenylene (THAP), and copper phthalocyan
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摘要 :
The synthesis and X-ray characterization of two new dialkynylated diazatetracenes and the corresponding N,N-dihydrodiazatetracenes are reported. The dialkynylated heteroacenes are packed in a brick-wall motif that enforces signifi...
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The synthesis and X-ray characterization of two new dialkynylated diazatetracenes and the corresponding N,N-dihydrodiazatetracenes are reported. The dialkynylated heteroacenes are packed in a brick-wall motif that enforces significant overlap of their jr-
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Electrical or chemical doping of molecular films is an efficient means of improving and controlling charge injection and carrier transport in organic devices. Recent work demonstrated that bis(cyclopentadienyl)cobalt(II) (cobaltoc...
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Electrical or chemical doping of molecular films is an efficient means of improving and controlling charge injection and carrier transport in organic devices. Recent work demonstrated that bis(cyclopentadienyl)cobalt(II) (cobaltocene, CoCp_2) efficiently dopes a
tris(thieno)hexaazatriphenylene (THAP) derivative, as shown by a 0.56 eV shift of the Fermi level toward the empty states and an increase of current density by a factor of 10~3 over undoped THAP devices. In this work, a combination of x-ray photoemission spectroscopy and Rutherford backscattering is used to elucidate the details of dopant incorporation into bulk films. Cobaltocene is observed to codeposit into the THAP matrix in a controllable manner, with preferential adsorption of the dopant onto the surface of the host film. In the case of CoCp_2-doped tris(8-hydroxy-quinolinato) aluminum (Alq_3) films, negligible amounts of the dopant are found in the bulk matrix and on the film surface, resulting in minimal improvements in the electrical characteristics of doped Alq_3 films. The process of CoCp_2 adsorption onto a film surface or the evolving surface of a growing film which leads to dopant incorporation is likely assisted by charge transfer from cobaltocene to the host material, resulting in ion pairing between the dopant and host.
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Imine-linked two-dimensional covalent organic frameworks (2D COFs) are crystalline polymer networks with enhanced stability compared to boronate ester-linked systems and with broad monomer scope. They are traditionally prepared by...
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Imine-linked two-dimensional covalent organic frameworks (2D COFs) are crystalline polymer networks with enhanced stability compared to boronate ester-linked systems and with broad monomer scope. They are traditionally prepared by condensing polyfunctional aldehydes and amines at elevated temperature in a mixture of organic solvents and aqueous CH_3C0_2H, which catalyzes imine formation and exchange. Here we employ metal triflates, which are water-tolerant Lewis acids, to accelerate 2D imine-linked COF synthesis and improve their materials quality. Low catalyst loadings provide crystalline polymer networks in nearly quantitative yields. These conditions are demonstrated for several COFs, including heteroatom-containing systems of interest for optoelectronic applications.
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