A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors (OFETs). Thin films of pentacene are the most mobile molecular films known to date. Thi...A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors (OFETs). Thin films of pentacene are the most mobile molecular films known to date. This paper reported that the pentacene sample was successfully synthesized. The purity of pentacene is up to 95%. The results of a joint experimental investigation based on a combination of infrared absorption spectra, mass spectra (MS), element analysis, x-ray diffraction (XRD) and atom force microscopy (AFM). The authors fabricated OFET with the synthesized pentacene. Its field effect mobility is about 1.23 cm^2/(V·s) and on-off ratio is above 10^6.展开更多
This paper investigates the morphology and crystallization properties of the two crystalline phases of pentacene grown by thermal evaporation on p^+-Si substrates at room temperature by the methods of atomic force mi...This paper investigates the morphology and crystallization properties of the two crystalline phases of pentacene grown by thermal evaporation on p^+-Si substrates at room temperature by the methods of atomic force microscopy and x-ray diffraction. This kind of substrate induces a thin film phase and a triclinic phase which are formed directly onto p^+-Si substrates and constitute a layer consisting of faceted grains with a step height between terraces of 15.8A(1A=0.1 nm) and 14.9A, respectively. Above the critical thickness of the thin film phase, lamellar structures are found with an increasing fraction with the increase of the film thickness. When the film thickness is fixed, the fraction of lamellar structures increases with the increase of annealing temperature. These lamellar structures are identified as the second phase with a interplanar distance of 14.9A corresponding to the pentacene triclinic phase. Furthermore, the thin film phase consisting of several micrometre sized uniformly oriented grains at an annealing temperature of less than 80℃ and a deposition rate of 0.6A/s is observed.展开更多
We introduced a dual electron accepting layer composed of tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) and MoO3 for thermoelectric devices based on a pentacene layer. We found that the power factor is enhanced by ...We introduced a dual electron accepting layer composed of tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) and MoO3 for thermoelectric devices based on a pentacene layer. We found that the power factor is enhanced by placing an F4-TCNQ layer directly in contact with the pentacene layer and it is also enhanced by placing a MoO3 layer between the F4-TCNQ layer and the Au electrode. By examining the contact resistance using a field effect transistor and a hole-only diode, we confirmed that the hole injection is improved due to the reduction of contact resistance at the interface between the MoO3 layer and the Au electrode.展开更多
High performance pentacene organic thin film transistors (OTFT) were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass...High performance pentacene organic thin film transistors (OTFT) were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass substrate with S-D electrode pattern made from ITO by means of thermal evaporation through self-organized process. The threshold voltage VTH was -2.75±0.1V in 0-50V range, and that subthreshold slopes were 0.42±0.05V/dec. The field-effect mobility (μEF) of OTFT device increased with the increase of VDS, but the μEF of OTFT device increased and then decreased with increased VGS when VDS was kept constant. When VDS was -50V, on/off current ratio was 0.48×10^5 and subthreshold slope was 0.44V/dec. The μEF was 1.10cm^2/(V.s), threshold voltage was -2.71V for the OTFT device.展开更多
We chose pentacene as a hole injection layer(HIL) to fabricate the high performance blue fluorescent organic lightemitting devices(OLEDs). We found that the carrier mobility of the pentacene thin films could be ef...We chose pentacene as a hole injection layer(HIL) to fabricate the high performance blue fluorescent organic lightemitting devices(OLEDs). We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120℃. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120℃ annealed pentacene film and n-doped electron transport layer(ETL) presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m^2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.展开更多
Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increase...Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increased by RPAD comparing to that by non-excited hydrogen gas supply whereas thermal evaporation rate of pentacene from crucible was same in the both process. DFM and XRD studies showed the grain laterally grew in the thin film phase with the size above 10 μm by RPAD. First-principles molecular orbital calculations suggested pentacene is evaporated from crucible as the trimer or larger cluster but atomic hydrogen penetrated into the cluster enhances cracking of pentacene clusters to the monomer.展开更多
In this contribution, we report on the effect of pentacene thickness and temperature on the performance of top gate transistors. We first investigated the temperature dependence of the transport properties in the temp...In this contribution, we report on the effect of pentacene thickness and temperature on the performance of top gate transistors. We first investigated the temperature dependence of the transport properties in the temperature range of 258 K - 353 K. The electrical characteristics showed that the threshold voltage (VT) and the onset voltage (Von) remain unchanged. However, the subthreshold current (Ioff), the on-current (Ion) and the field effect mobility (μ) are highly affected with a slight deterioration of subthreshold slope. We observed Arrhenius-like behavior suggesting a thermally activated mobility with an activation energy EA = 68 meV. Moreover the dependence of the charge carrier mobility on the organic semiconductor thickness has also been studied. The mobility decreased as the pentacene thickness increases whereas the threshold voltage and Ioff current remain minimally affected. In order to understand the transport properties and in view to put in light morphology peculiarities of pentacene, AFM images were performed. It turns out that the pentacene grain sizes are smaller and disorganized as the film thickness increases, and charge carriers are more prone to be trapped, leading to decrease the field effect mobility and the Ion current. The devices were also tested under bias stress and the transistors with low thicknesses exhibited a relatively good electrical stability compared to those with high pentacene thicknesses. This work points out the influence of temperature, semiconductor thickness and bias stress effect on the device performance and stability of transistor using top gate configuration.展开更多
This study deals with electrical instability under bias stress in pentacene-based transistors with gate dielectrics deposited by a lamination process. Mylar film is laminated onto a polyethylene terephthalate (PET) su...This study deals with electrical instability under bias stress in pentacene-based transistors with gate dielectrics deposited by a lamination process. Mylar film is laminated onto a polyethylene terephthalate (PET) substrate, on which aluminum (Al) gate is deposited, followed by evaporation of organic semiconductor and gold (Au) source/drain contacts in bottom gate top contact configuration (Device 1). In order to compare the influence of the semiconductor/dielectric interface, a second organic transistor (Device 2) which is different from the Device 1 by the deposition of an intermediate layer of polymethyl methacrylate (PMMA) onto the laminated Mylar dielectric and before evaporating pentacene layer is fabricated. The critical device parameters such as threshold voltage (V<sub>T</sub>), subthreshold slope (S), mobility (μ), onset voltage (V<sub>on</sub>) and I<sub>on</sub>/I<sub>off</sub> ratio have been studied. The results showed that the recorded hysteresis depend on the pentacene morphology. Moreover, after bias stress application, the electrical parameters are highly modified for both devices according to the regimes in which the transistors are operating. In ON state regime, Device 1 showed a pronounced threshold voltage shift associated to charge trapping, while keeping the μ, I<sub>off</sub> current and S minimally affected. Regardless of whether Device 2 exhibited better electrical performances and stability in ON state, we observed a bias stress-induced increase of depletion current and subthreshold slope in subthreshold region, a sign of defect creation. Both devices showed onset voltage shift in opposite direction.展开更多
Fullerene assembling with specific donor molecules would yield multi-functional metamaterials via the collective behavior,wherein linear acenes are widely used as donor molecules to construct the charge‐transfer hete...Fullerene assembling with specific donor molecules would yield multi-functional metamaterials via the collective behavior,wherein linear acenes are widely used as donor molecules to construct the charge‐transfer heterojunction structure with fullerene.However,they are generally prepared by vacuum deposition due to the insoluble property of high‐performance linear acenes molecules in common solvents,which makes the construction of fullerene with insoluble donor molecules still be a big challenge in the solution‐processed method.To this end,chemical modification provides an effective solution‐processed strategy to construct donor and acceptor systems.Here,the C60‐pentacene is assembled into controllable flower‐like superstructures by the surface grafting method.It is found that the nanofeatures of the microflowers could be regulated by temperature,resulting in dense‐flakes morphology at room temperature and loose flakes at high temperatures.Furthermore,the dense‐flakes microflowers structures with less mass but better crystalline structure exhibit better optoelectronic properties.Our results reveal an effective control on the nanofeatures of the self‐assembled fullerenes complex super-structures and their role for the optoelectronic performance,which may promote the exploring of fullerene superstructures as photodetectors.展开更多
We investigated the properties of C_(60)-based organic field-enect transistors(OFETs)(?) a pentacene passivation layer inserted between the C_(60) active layer and the gate dielectric.After modification of th...We investigated the properties of C_(60)-based organic field-enect transistors(OFETs)(?) a pentacene passivation layer inserted between the C_(60) active layer and the gate dielectric.After modification of the pentacene passivation layer,the performance of the devices was considerably improved compared to C_(60)-based OFETs with only a PMMA dielectric.The peak field-effect mobility was up to 1.01 cm^2/(V·s) and the on/off ratio shifted to 10~4.This result indicates that using a pentacene passivation layer is an effective way to improve the performance of N-type OFETs.展开更多
Structures and nonlinear optical(NLO) properties of eleven new Lin-Pm(n=1-5) species were investigated in detail with the help of ab initio computation, in which one to the maximum five Li atoms are doped over the...Structures and nonlinear optical(NLO) properties of eleven new Lin-Pm(n=1-5) species were investigated in detail with the help of ab initio computation, in which one to the maximum five Li atoms are doped over the polycyclic π-conjugated pentacene. These Li-doped pentacene systems exhibit large adsorption energies(ca. 107.0--141.3 kJ/mol) and considerable first hyperpolarizabilities(even up to 4.1×10^4 a.u.), where the number of Li atoms, the doping site, and the distance between the neighboring Li atoms have important impacts on the flo value. In the doped pentacene systems with less Li atoms(one or two), the improvement of β10 value can be attributed to the simple transfer of the charge from Li atom to pentacene. Differently, doped more Li atoms(three to five) can cause not only charge transfer but also excess electron, and this cooperation can endow the doped systems with the much larger first hyperpolarizabilities. These fascinating findings are advantageous for the design of new NLO materials based on the intriguing polycyclic π-conjugated systems.展开更多
We fabricate organic thin films using the copolymer of methyl methacrylate and glycidyl methacrylate (PMMA- GMA) as a gate dielectric with a simple top-contact structure. Copper phthalocyanine (CuPc) TFTs are fabr...We fabricate organic thin films using the copolymer of methyl methacrylate and glycidyl methacrylate (PMMA- GMA) as a gate dielectric with a simple top-contact structure. Copper phthalocyanine (CuPc) TFTs are fabricated and the influences of annealing on the performance are studied. The mobilities increase from 2.5 × 10^3 cm^2/Vs to 4.2 × 10^3 cm^2/Vs and threshold voltages decrease from -18 V to -10 V after annealing. The good performances of the devices approach those obtained with inorganic gate dielectric materials such as silicon dioxide under the same technical conditions. It is fully proven that PMMA-GMA is a competitive candidate as an excellent gate insulation layer.展开更多
The synthesis and characterization of platinum(II)and palladium(II)complexes bearing two(dimers Pt(L_(pc))_(2)Cl_(2)and Pd(L_(pc))_(2)Cl_(2)),one(monomers Pt(L_(pc))(L_(ref))Cl_(2)and Pd(L_(pc))(L_(ref))-Cl_(2)),or no...The synthesis and characterization of platinum(II)and palladium(II)complexes bearing two(dimers Pt(L_(pc))_(2)Cl_(2)and Pd(L_(pc))_(2)Cl_(2)),one(monomers Pt(L_(pc))(L_(ref))Cl_(2)and Pd(L_(pc))(L_(ref))-Cl_(2)),or no(reference compounds Pt(L_(ref))_(2)Cl_(2)and Pd(L_(ref))_(2)Cl_(2))pentacene-based pyridyl ligands are presented.Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in compar-ison to the monomer and model compounds.Our results document that despite enhanced spin−orbit coupling from the presence of heavy atoms,intramolecular singlet fission(iSF)is not challenged by intersystem crossing.iSF thus yields correlated triplet pairs and even uncorrelated triplet excited states upon decoherence.Importantly,significant separation of the two pentacenyl groups facilitates decoupling of the two chromophores.Furthermore,the mechanism of iSF is altered depending on the respective metal center,that is,Pt(II)versus Pd(II).The dimer based on Pt(II),Pt(L_(pc))2Cl_(2),exhibits a direct pathway for the iSF and forms a correlated triplet pair with singlet−quintet spin-mixing within 10 ns in variable solvents.On the other hand,the dimer based on Pd(II),Pd(L_(pc))_(2)Cl_(2),leads to charge transfer mixing during the population of the correlated triplet pair that is dependent on solvent polarity.Moreover,Pd(L_(pc))_(2)Cl_(2)gives rise to a stable equilibrium between singlet and quintet correlated triplet pairs with lifetimes of up to 170 ns.Inherent differences in the size and polarizability,when contrasting platinum(II)with palladium(II),are the most likely rationale for the underlying trends.展开更多
To isolate the active layer from air, double organic layer organic field-effect transistors have been fabricated, based on a two-step vacuum-deposition process. Pentacene acted as the active layer, and subsequently, C...To isolate the active layer from air, double organic layer organic field-effect transistors have been fabricated, based on a two-step vacuum-deposition process. Pentacene acted as the active layer, and subsequently, CuPc was deposited above the pentacene and served as a protecting layer for the active layer. Due to the same electrical characteristics but different morphologies, the bilayer structure was effective in decreasing the contamination of impurities and gas, and then improved the device stability in air.展开更多
The structure of organic thin film transistors (OTFTs) is optimized by introducing a floating gate into the gate dielectric to reduce the threshold voltage of OTFTs. Then the optimized device is simulated, and the s...The structure of organic thin film transistors (OTFTs) is optimized by introducing a floating gate into the gate dielectric to reduce the threshold voltage of OTFTs. Then the optimized device is simulated, and the simulation results show that the threshold voltage of optimized device is reduced by about 10 V. The reduction of the threshold voltage is helpful and useful for the application of OTFTs in many areas. In addition, this way of reducing the threshold voltage of OTFT is compatible with traditional silicon technology and can be used in manufacturing.展开更多
基金Supported by the State Key Development Program for Basic Research of China (2003CB716204) The Education Department for International Cooperation (2006029501)
基金Project supported by the National Natural Science Foundation of China (Grant No 60676033)
文摘A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors (OFETs). Thin films of pentacene are the most mobile molecular films known to date. This paper reported that the pentacene sample was successfully synthesized. The purity of pentacene is up to 95%. The results of a joint experimental investigation based on a combination of infrared absorption spectra, mass spectra (MS), element analysis, x-ray diffraction (XRD) and atom force microscopy (AFM). The authors fabricated OFET with the synthesized pentacene. Its field effect mobility is about 1.23 cm^2/(V·s) and on-off ratio is above 10^6.
基金Project supported by the National High Technology Research and Development Program (863 plan) of China (Grant No2006AA03Z0412)the National Natural Science Foundation of China (Grant Nos 60576016 and 10774013)+4 种基金the Excellent Doctor’s Science and Technology Innovation Foundation of Beijing Jiaotong University (Grant No 48024)The Research Fund forthe Youth Scholars of the Doctoral Program of Higher Education (Grant No 20070004031)the Beijing NOVA program (GrantNo 2007A024)the Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministrythe Foundation of Beijing Jiaotong University (Grant No 2005SM057)
文摘This paper investigates the morphology and crystallization properties of the two crystalline phases of pentacene grown by thermal evaporation on p^+-Si substrates at room temperature by the methods of atomic force microscopy and x-ray diffraction. This kind of substrate induces a thin film phase and a triclinic phase which are formed directly onto p^+-Si substrates and constitute a layer consisting of faceted grains with a step height between terraces of 15.8A(1A=0.1 nm) and 14.9A, respectively. Above the critical thickness of the thin film phase, lamellar structures are found with an increasing fraction with the increase of the film thickness. When the film thickness is fixed, the fraction of lamellar structures increases with the increase of annealing temperature. These lamellar structures are identified as the second phase with a interplanar distance of 14.9A corresponding to the pentacene triclinic phase. Furthermore, the thin film phase consisting of several micrometre sized uniformly oriented grains at an annealing temperature of less than 80℃ and a deposition rate of 0.6A/s is observed.
基金supported by the New Energy and Industrial Technology Development Organization(NEDO)the Funding Program for World-Leading Innovative R&D on Science and Technology(FIRST)the International Institute for Carbon Neutral Energy Research(WPI-I2CNER)sponsored by MEXT
文摘We introduced a dual electron accepting layer composed of tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) and MoO3 for thermoelectric devices based on a pentacene layer. We found that the power factor is enhanced by placing an F4-TCNQ layer directly in contact with the pentacene layer and it is also enhanced by placing a MoO3 layer between the F4-TCNQ layer and the Au electrode. By examining the contact resistance using a field effect transistor and a hole-only diode, we confirmed that the hole injection is improved due to the reduction of contact resistance at the interface between the MoO3 layer and the Au electrode.
基金supported by the National Natural Science Foundation of China (Grant No 60576016)the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)+3 种基金the Beijing Natural Science Foundation of China (Grant No 2073030)the National Grand Fundamental Research 973 Program of China (Grant No 2003CB314707)the National Natural Science Foundation of China (Grant No 10434030)the Excellent Doctor's Science and Technology Innovation Foundation of Beijing Jiaotong University of China (Grant No 48024)
文摘High performance pentacene organic thin film transistors (OTFT) were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass substrate with S-D electrode pattern made from ITO by means of thermal evaporation through self-organized process. The threshold voltage VTH was -2.75±0.1V in 0-50V range, and that subthreshold slopes were 0.42±0.05V/dec. The field-effect mobility (μEF) of OTFT device increased with the increase of VDS, but the μEF of OTFT device increased and then decreased with increased VGS when VDS was kept constant. When VDS was -50V, on/off current ratio was 0.48×10^5 and subthreshold slope was 0.44V/dec. The μEF was 1.10cm^2/(V.s), threshold voltage was -2.71V for the OTFT device.
基金Project supported by the National Natural Science Foundation of China(Grant No.60906022)the Natural Science Foundation of Tianjin,China(Grant No.10JCYBJC01100)+1 种基金the Key Science and Technology Support Program of Tianjin,China(Grant No.14ZCZDGX00006)the National High Technology Research and Development Program of China(Grant No.2013AA014201)
文摘We chose pentacene as a hole injection layer(HIL) to fabricate the high performance blue fluorescent organic lightemitting devices(OLEDs). We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120℃. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120℃ annealed pentacene film and n-doped electron transport layer(ETL) presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m^2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.
文摘Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increased by RPAD comparing to that by non-excited hydrogen gas supply whereas thermal evaporation rate of pentacene from crucible was same in the both process. DFM and XRD studies showed the grain laterally grew in the thin film phase with the size above 10 μm by RPAD. First-principles molecular orbital calculations suggested pentacene is evaporated from crucible as the trimer or larger cluster but atomic hydrogen penetrated into the cluster enhances cracking of pentacene clusters to the monomer.
基金the FIRST(Fonds d’Impulsion pour la Recherche Scientifique et Technique)programCEA-MITIC(Centre d’excellence en Mathematiques,Informatique et TIC)for financial support.
文摘In this contribution, we report on the effect of pentacene thickness and temperature on the performance of top gate transistors. We first investigated the temperature dependence of the transport properties in the temperature range of 258 K - 353 K. The electrical characteristics showed that the threshold voltage (VT) and the onset voltage (Von) remain unchanged. However, the subthreshold current (Ioff), the on-current (Ion) and the field effect mobility (μ) are highly affected with a slight deterioration of subthreshold slope. We observed Arrhenius-like behavior suggesting a thermally activated mobility with an activation energy EA = 68 meV. Moreover the dependence of the charge carrier mobility on the organic semiconductor thickness has also been studied. The mobility decreased as the pentacene thickness increases whereas the threshold voltage and Ioff current remain minimally affected. In order to understand the transport properties and in view to put in light morphology peculiarities of pentacene, AFM images were performed. It turns out that the pentacene grain sizes are smaller and disorganized as the film thickness increases, and charge carriers are more prone to be trapped, leading to decrease the field effect mobility and the Ion current. The devices were also tested under bias stress and the transistors with low thicknesses exhibited a relatively good electrical stability compared to those with high pentacene thicknesses. This work points out the influence of temperature, semiconductor thickness and bias stress effect on the device performance and stability of transistor using top gate configuration.
文摘This study deals with electrical instability under bias stress in pentacene-based transistors with gate dielectrics deposited by a lamination process. Mylar film is laminated onto a polyethylene terephthalate (PET) substrate, on which aluminum (Al) gate is deposited, followed by evaporation of organic semiconductor and gold (Au) source/drain contacts in bottom gate top contact configuration (Device 1). In order to compare the influence of the semiconductor/dielectric interface, a second organic transistor (Device 2) which is different from the Device 1 by the deposition of an intermediate layer of polymethyl methacrylate (PMMA) onto the laminated Mylar dielectric and before evaporating pentacene layer is fabricated. The critical device parameters such as threshold voltage (V<sub>T</sub>), subthreshold slope (S), mobility (μ), onset voltage (V<sub>on</sub>) and I<sub>on</sub>/I<sub>off</sub> ratio have been studied. The results showed that the recorded hysteresis depend on the pentacene morphology. Moreover, after bias stress application, the electrical parameters are highly modified for both devices according to the regimes in which the transistors are operating. In ON state regime, Device 1 showed a pronounced threshold voltage shift associated to charge trapping, while keeping the μ, I<sub>off</sub> current and S minimally affected. Regardless of whether Device 2 exhibited better electrical performances and stability in ON state, we observed a bias stress-induced increase of depletion current and subthreshold slope in subthreshold region, a sign of defect creation. Both devices showed onset voltage shift in opposite direction.
基金Beijing National Laboratory for Molecular Sciences,Grant/Award Number:BNLMS202006National Natural Science Foundation of China,Grant/Award Numbers:21875108,62004138+1 种基金Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20191289Instrument&Equipment Open Funding of Nanjing University of Science and Technology。
文摘Fullerene assembling with specific donor molecules would yield multi-functional metamaterials via the collective behavior,wherein linear acenes are widely used as donor molecules to construct the charge‐transfer heterojunction structure with fullerene.However,they are generally prepared by vacuum deposition due to the insoluble property of high‐performance linear acenes molecules in common solvents,which makes the construction of fullerene with insoluble donor molecules still be a big challenge in the solution‐processed method.To this end,chemical modification provides an effective solution‐processed strategy to construct donor and acceptor systems.Here,the C60‐pentacene is assembled into controllable flower‐like superstructures by the surface grafting method.It is found that the nanofeatures of the microflowers could be regulated by temperature,resulting in dense‐flakes morphology at room temperature and loose flakes at high temperatures.Furthermore,the dense‐flakes microflowers structures with less mass but better crystalline structure exhibit better optoelectronic properties.Our results reveal an effective control on the nanofeatures of the self‐assembled fullerenes complex super-structures and their role for the optoelectronic performance,which may promote the exploring of fullerene superstructures as photodetectors.
基金supported by the National Natural Science Foundation of China(No.61076065)the Natural Science Foundation of Tianjin City,China(No.07JCYBJC12700)
文摘We investigated the properties of C_(60)-based organic field-enect transistors(OFETs)(?) a pentacene passivation layer inserted between the C_(60) active layer and the gate dielectric.After modification of the pentacene passivation layer,the performance of the devices was considerably improved compared to C_(60)-based OFETs with only a PMMA dielectric.The peak field-effect mobility was up to 1.01 cm^2/(V·s) and the on/off ratio shifted to 10~4.This result indicates that using a pentacene passivation layer is an effective way to improve the performance of N-type OFETs.
基金Supported by the National Basic Research Program of China(No.2012CB932800), the National Natural Science Foundation of China(Nos.21103065, 21373099, 21403083, 21173097), and the Project of the Ministry of Education of China(Nos. 20110061120024, 20130061110020).
文摘Structures and nonlinear optical(NLO) properties of eleven new Lin-Pm(n=1-5) species were investigated in detail with the help of ab initio computation, in which one to the maximum five Li atoms are doped over the polycyclic π-conjugated pentacene. These Li-doped pentacene systems exhibit large adsorption energies(ca. 107.0--141.3 kJ/mol) and considerable first hyperpolarizabilities(even up to 4.1×10^4 a.u.), where the number of Li atoms, the doping site, and the distance between the neighboring Li atoms have important impacts on the flo value. In the doped pentacene systems with less Li atoms(one or two), the improvement of β10 value can be attributed to the simple transfer of the charge from Li atom to pentacene. Differently, doped more Li atoms(three to five) can cause not only charge transfer but also excess electron, and this cooperation can endow the doped systems with the much larger first hyperpolarizabilities. These fascinating findings are advantageous for the design of new NLO materials based on the intriguing polycyclic π-conjugated systems.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60307002 and 6057054.
文摘We fabricate organic thin films using the copolymer of methyl methacrylate and glycidyl methacrylate (PMMA- GMA) as a gate dielectric with a simple top-contact structure. Copper phthalocyanine (CuPc) TFTs are fabricated and the influences of annealing on the performance are studied. The mobilities increase from 2.5 × 10^3 cm^2/Vs to 4.2 × 10^3 cm^2/Vs and threshold voltages decrease from -18 V to -10 V after annealing. The good performances of the devices approach those obtained with inorganic gate dielectric materials such as silicon dioxide under the same technical conditions. It is fully proven that PMMA-GMA is a competitive candidate as an excellent gate insulation layer.
文摘The synthesis and characterization of platinum(II)and palladium(II)complexes bearing two(dimers Pt(L_(pc))_(2)Cl_(2)and Pd(L_(pc))_(2)Cl_(2)),one(monomers Pt(L_(pc))(L_(ref))Cl_(2)and Pd(L_(pc))(L_(ref))-Cl_(2)),or no(reference compounds Pt(L_(ref))_(2)Cl_(2)and Pd(L_(ref))_(2)Cl_(2))pentacene-based pyridyl ligands are presented.Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in compar-ison to the monomer and model compounds.Our results document that despite enhanced spin−orbit coupling from the presence of heavy atoms,intramolecular singlet fission(iSF)is not challenged by intersystem crossing.iSF thus yields correlated triplet pairs and even uncorrelated triplet excited states upon decoherence.Importantly,significant separation of the two pentacenyl groups facilitates decoupling of the two chromophores.Furthermore,the mechanism of iSF is altered depending on the respective metal center,that is,Pt(II)versus Pd(II).The dimer based on Pt(II),Pt(L_(pc))2Cl_(2),exhibits a direct pathway for the iSF and forms a correlated triplet pair with singlet−quintet spin-mixing within 10 ns in variable solvents.On the other hand,the dimer based on Pd(II),Pd(L_(pc))_(2)Cl_(2),leads to charge transfer mixing during the population of the correlated triplet pair that is dependent on solvent polarity.Moreover,Pd(L_(pc))_(2)Cl_(2)gives rise to a stable equilibrium between singlet and quintet correlated triplet pairs with lifetimes of up to 170 ns.Inherent differences in the size and polarizability,when contrasting platinum(II)with palladium(II),are the most likely rationale for the underlying trends.
基金Project supported by the State Key Development Program for Basic Research of China(No.2006CB806204)the National Natural Science Foundation of China(Nos.60676001,60676008)
文摘To isolate the active layer from air, double organic layer organic field-effect transistors have been fabricated, based on a two-step vacuum-deposition process. Pentacene acted as the active layer, and subsequently, CuPc was deposited above the pentacene and served as a protecting layer for the active layer. Due to the same electrical characteristics but different morphologies, the bilayer structure was effective in decreasing the contamination of impurities and gas, and then improved the device stability in air.
文摘The structure of organic thin film transistors (OTFTs) is optimized by introducing a floating gate into the gate dielectric to reduce the threshold voltage of OTFTs. Then the optimized device is simulated, and the simulation results show that the threshold voltage of optimized device is reduced by about 10 V. The reduction of the threshold voltage is helpful and useful for the application of OTFTs in many areas. In addition, this way of reducing the threshold voltage of OTFT is compatible with traditional silicon technology and can be used in manufacturing.