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1.
ACS Appl Mater Interfaces ; 11(31): 28052-28059, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31304744

RESUMO

Inkjet-printed thin-film transistors (TFTs) for active-matrix light-emitting diode display are drawing much attention for the advantages of low material waste and simple fabrication processes without vacuum deposition and photolithography steps. Herein, for the first time, solution-processed quantum-dot light-emitting diode (QLED) array displays driven with the inkjet-printed oxide TFT backplane were realized and demonstrated using a general "solvent printing" method. To suppress nanopore formation in the thick oxide films, carbon-free aqueous inks were employed for gate dielectrics. No nanopore was found in the whole 120 nm-thick gate dielectrics. However, compared to the organic inks, the aqueous inks have very low viscosity, resulting in uncontrollable ink spreading especially in transline printing. The ink easily shrinks on the low-surface-energy area and spreads on the high-surface-energy area, leading to serious uniformity problems (the upper lines even break at the top of underlying lines). To solve the problem, a "solvent printing" method was employed to form coffee-line surface-energy patterns, which were uniform without shape distortion. The surface-energy patterns can restrain the ink spreading and tune the morphology of the printed films. As a result, multilayer TFT arrays with ideal shapes were achieved. The mobilities of the printed top-gate TFTs in the backplane array were 3.13 ± 0.87 cm2 V-1 s-1 for switching TFTs and 2.22 ± 0.38 cm2 V-1 s-1 for driving TFTs. Finally, an active-matrix red QLED character display based on the printed oxide TFT backplane and solution-processed QLEDs was demonstrated. The "solvent printing" method opens a general route for inkjet-printed multilayer electronic devices.

2.
Nanotechnology ; 30(31): 312001, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-30974423

RESUMO

Driven by the rapid development of novel active-matrix displays, thin-film transistors (TFTs) based on metal-oxide (MO) semiconductors have drawn great attention during recent years. N-type MO TFTs manufactured through vacuum-based processes have the advantages of higher mobility compared to the amorphous silicon TFTs, better uniformity and lower processing temperature compared to the polysilicon TFTs, and visible light transparency which is suitable for transparent electronic devices, etc. However, the fabrication cost is high owing to the expensive and complicated vacuum-based systems. In contrast, solution process has the advantages of low cost, high throughput, and easy chemical composition control. In the first part of this review, a brief introduction of solution-processed MO TFTs is given, and the main issues and challenges encountered in this field are discussed. The recent advances in channel layer engineering to obtain the state-of-the-art solution-processed MO TFTs are reviewed and summarized. Afterward, a detailed discussion of the direct patterning methods is presented, including the direct photopatterning and printing techniques. Next, the effect of gate dielectric materials and their interfaces on the performance of the resulting TFTs are surveyed. The last topic is the various applications of solution-processed MO TFTs, from novel displays to sensing, memory devices, etc. Finally, conclusions are drawn and future expectations for solution-processed MO TFTs and their applications are described.

3.
Chem Sci ; 10(1): 227-232, 2019 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-30713634

RESUMO

Recently, the study of flexible (elastically bendable and plastically bendable) organic single crystals has become a hot research field in crystal engineering. In general, crystal elasticity and plasticity are incompatible with each other. Different from the applications of fluorescent crystals, the applications of room-temperature phosphorescence (RTP) materials generally ignore the crystallographic nature of large single crystals. Herein, we creatively combine elasticity and plasticity based on one RTP crystal 4,4'-dibromobenzil DBBZL. The in-depth study of the irreversible transformation between elastic bending and plastic bending provided important insights into the mechanism of both elastically bendable crystals and plastically bendable crystals in crystal engineering. The DBBZL crystal exhibits elastic bending (reversible) under external stress, whereas it shows plastic bending (irreversible) after excessive bending. Notably, the first phosphorescent optical waveguides of large single RTP crystals are realized not only in straight state, but also in elastic bent state and plastic bent state.

4.
ACS Nano ; 12(5): 4624-4629, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29741872

RESUMO

Light-emitting field-effect transistors (LEFETs) have attained great attention due to their special characteristics of both the switching capacity and the electroluminescence capacity. However, high-performance LEFETs with high mobility, high brightness, and high efficiency have not been realized due to the difficulty in developing high electron and hole mobility materials with suitable band structures. In this paper, quantum dot hybrid LEFETs (QD-HLEFETs) combining high-luminous-efficiency quantum dots (QDs) and a solution-processed scandium-incorporated indium oxide (Sc:In2O3) semiconductor were demonstrated. The red QD-HLEFET showed high electrical and optical performance with an electron mobility of 0.8 cm2 V-1 s-1, a maximum brightness of 13 400 cd/m2, and a maximum external quantum efficiency of 8.7%. The high performance of the QD-HLEFET is attributed to the good energy band matching between Sc:In2O3 and QDs and the balanced hole and electron injection (less exciton nonradiative recombination). In addition, incorporation of Sc into In2O3 can suppress the oxygen vacancy and free carrier generation and brings about excellent current and optical modulation (the on/off current ratio is 105 and the on/off brightness ratio is 106).

5.
Polymers (Basel) ; 10(1)2018 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-30966088

RESUMO

Two large band-gap polymers (PTPACF and PTPA2CF) based on polytriphenylamine derivatives with the introduction of electron-withdrawing trifluoromethyl groups were designed and prepared by Suzuki polycondensation reaction. The chemical structures, thermal, optical and electrochemical properties were characterized in detail. From the UV-visible absorption spectra, the PTPACF and PTPA2CF showed the optical band gaps of 2.01 and 2.07 eV, respectively. The cyclic voltammetry (CV) measurement displayed the deep highest occupied molecular orbital (HOMO) energy levels of -5.33 and -5.38 eV for PTPACF and PTPA2CF, respectively. The hole mobilities, determined by field-effect transistor characterization, were 2.5 × 10-3 and 1.1 × 10-3 cm² V-1 S-1 for PTPACF and PTPA2CF, respectively. The polymer solar cells (PSCs) were tested under the conventional device structure of ITO/PEDOT:PSS/polymer:PC71BM/PFN/Al. All of the PSCs showed the high open circuit voltages (Vocs) with the values approaching 1 V. The PTPACF and PTPA2CF based PSCs gave the power conversion efficiencies (PCEs) of 3.24% and 2.40%, respectively. Hence, it is a reliable methodology to develop high-performance large band-gap polymer donors with high Vocs through the feasible side-chain modification.

6.
Materials (Basel) ; 10(1)2017 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28772385

RESUMO

The effect of intrinsic stress on the structure and physical properties of silicon-tin-oxide (STO) films have been investigated. Since a state of tensile stress is available in as-deposited films, the value of stress can be exponentially enhanced when the annealing temperature is increased. The tensile stress is able to not only suppress the crystallization and widen the optical band gap of STO films, but also reduce defects of STO films. In this report, the good electrical performance of STO thin-film transistors (TFTs) can be obtained when annealing temperature is 450 °C. This includes a value of saturation mobility that can be reached at 6.7 cm²/Vs, a ratio of Ion/Ioff as 7.34 × 107, a steep sub-threshold swing at 0.625 V/decade, and a low trap density of 7.96 × 1011 eV-1·cm-2, respectively.

7.
Materials (Basel) ; 10(3)2017 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-28772579

RESUMO

Bottom-gate all-aluminum thin film transistors with multi conductor/insulator nanometer heterojunction were investigated in this article. Alumina (Al2O3) insulating layer was deposited on the surface of aluminum doping zinc oxide (AZO) conductive layer, as one AZO/Al2O3 heterojunction unit. The measurements of transmittance electronic microscopy (TEM) and X-ray reflectivity (XRR) revealed the smooth interfaces between ~2.2-nm-thick Al2O3 layers and ~2.7-nm-thick AZO layers. The devices were entirely composited by aluminiferous materials, that is, their gate and source/drain electrodes were respectively fabricated by aluminum neodymium alloy (Al:Nd) and pure Al, with Al2O3/AZO multilayered channel and AlOx:Nd gate dielectric layer. As a result, the all-aluminum TFT with two Al2O3/AZO heterojunction units exhibited a mobility of 2.47 cm²/V·s and an Ion/Ioff ratio of 106. All processes were carried out at room temperature, which created new possibilities for green displays industry by allowing for the devices fabricated on plastic-like substrates or papers, mainly using no toxic/rare materials.

8.
Chem Commun (Camb) ; 53(48): 6436-6439, 2017 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-28560377

RESUMO

In this report, a simple and general chemical route for fabricating MO semiconducting films at a relatively low temperature without any fuel additives or special annealing steps was demonstrated. The precursor, which consisted of perchlorate, nitrate, and water, is easily converted into In2O3 at an annealing temperature of 250 °C due to oxygen radical assisted decomposition and generation of a large amount of heat. It is found that perchlorate salt can decompose and form an oxide film with high quality at a lower temperature when assisted by nitrate salt. The optimized In2O3-TFT fabricated via this precursor exhibits a saturation mobility of 14.5 cm2 V-1 s-1. Furthermore, this approach has been expanded to the fabrication of ZnO films and attained improved performance, indicating its universality.

9.
ACS Appl Mater Interfaces ; 9(9): 8194-8200, 2017 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-28230340

RESUMO

An array of inkjet-printed metal-oxide thin-film transistors (TFTs) is demonstrated for the first time with the assistance of surface-energy patterns prepared by printing pure solvent to etch the ultrathin hydrophobic layer. The surface-energy patterns not only restrained the spreading of inks but also provided a facile way to regulate the morphology of metal oxide films without optimizing ink formulation. The fully printed InGaO TFT devices in the array exhibited excellent electron transport characteristics with a maximum mobility of 11.7 cm2 V-1 s-1, negligible hysteresis, good uniformity, and good stability under bias stress. The new route lights a general way toward fully inkjet-printed metal-oxide TFT arrays.

10.
ACS Appl Mater Interfaces ; 9(8): 7315-7321, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28139913

RESUMO

In this study, we developed a ternary conjugated polymer, IFBT-TT, consisting of centrosymmetric indaceno[1,2-b:5,6-b']dithiophene and thieno[3,2-b]thiophene as the electron-donating units and an asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole as the electron-accepting unit. The target copolymer was synthesized using an acceptor-donor-acceptor (A-D-A) type of macromonomer, which gave the target copolymer a precisely defined D1-A-D2-A architecture. Theoretical simulation revealed that the IFBT-TT features C-H···N and F···S nonbonding interactions, leading to a highly rigid and planar molecular backbone. Although the spin-cast IFBT-TT films exhibited an amorphous morphology lacking in ordered structures, the fabricated field-effect transistors presented remarkable p-type transport properties with high mobility of up to 5.0 cm2 V-1 s-1 and excellent ambient stability. These observations highlight that the integration of a three-component D1-A-D2-A-type backbone framework is an effective molecular design strategy for high-mobility conjugated polymers.

11.
J Colloid Interface Sci ; 487: 68-72, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-27744171

RESUMO

The control of channel length is of great significance in the fabrication of thin film transistors (TFTs) with high-speed operation. However, achieving short channel on untreated glass by traditional piezoelectric inkjet printing is problematic due to the impacting and rebounding behaviors of droplet impinging on solid surface. Here a novel method was proposed to obtain short channel length on untreated glass by taking advantage of the difference in the retraction velocities on both sides of an ink droplet. In addition, droplets contact mechanism was first introduced in our work to explain the formation of short channel in the printing process. Through printing droplets array with optimized drop space and adjusting appropriate printing parameters, a 2.4µm of channel length for TFT, to the best of our knowledge, which is the shortest channel on substrate without pre-patterning, was achieved using piezoelectric inkjet printing. This study sheds light on the fabrication of short channel TFT for large size and high-resolution displays using inkjet printing technology.

12.
Sci Rep ; 6: 29055, 2016 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-27378163

RESUMO

Shrinking the device dimension has long been the pursuit of the semiconductor industry to increase the device density and operation speed. In the application of thin film transistors (TFTs), all-organic TFT arrays made by all-solution process are desired for low cost and flexible electronics. One of the greatest challenges is how to achieve ultrashort channel through a cost-effective method. In our study, ultrashort-channel devices are demonstrated by direct inkjet printing conducting polymer as source/drain and gate electrodes without any complicated substrate's pre-patterning process. By modifying the substrate's wettability, the conducting polymer's contact line is pinned during drying process which makes the channel length well-controlled. An organic TFT array of 200 devices with 2 µm channel length is fabricated on flexible substrate through all-solution process. The simple and scalable process to fabricate high resolution organic transistor array offers a low cost approach in the development of flexible and wearable electronics.

13.
ACS Appl Mater Interfaces ; 8(30): 19643-8, 2016 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-27420373

RESUMO

Short-channel electronic devices several micrometers in length are difficult to implement by direct inkjet printing due to the limitation of position accuracy of the common inkjet printer system and the spread of functional ink on substrates. In this report, metal oxide thin-film transistors (TFTs) with channel lengths of 3.5 ± 0.7 µm were successfully fabricated with a common inkjet printer without any photolithography steps. Hydrophobic CYTOP coffee stripes, made by inkjet-printing and plasma-treating processes, were utilized to define the channel area of TFTs with channel lengths as short as ∼3.5 µm by dewetting the inks of the source/drain (S/D) precursors. Furthermore, by introduction of an ultrathin layer of PVA to modify the S/D surfaces, the spreading of precursor ink of the InOx semiconductor layer was well-controlled. The inkjet-printed short-channel TFTs exhibited a maximum mobility of 4.9 cm(2) V(-1) s(-1) and an on/off ratio of larger than 10(9). This approach of fabricating short-channel TFTs by inkjet printing will promote the large-area fabrication of short-channel TFTs in a cost-effective manner.

14.
Sci Rep ; 6: 25000, 2016 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-27118177

RESUMO

Thin-film transistors (TFTs) with zirconium-doped indium oxide (ZrInO) semiconductor were successfully fabricated by an all-DC-sputtering method at room temperature. The ZrInO TFT without any intentionally annealing steps exhibited a high saturation mobility of 25.1 cm(2)V(-1)s(-1). The threshold voltage shift was only 0.35 V for the ZrInO TFT under positive gate bias stress for 1 hour. Detailed studies showed that the room-temperature ZrInO thin film was in the amorphous state with low carrier density because of the strong bonding strength of Zr-O. The room-temperature process is attractive for its compatibility with almost all kinds of the flexible substrates, and the DC sputtering process is good for the production efficiency improvement and the fabrication cost reduction.

15.
Materials (Basel) ; 9(8)2016 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-28773743

RESUMO

We report a high-performance amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor (TFT) with new copper-chromium (Cu-Cr) alloy source/drain electrodes. The TFT shows a high mobility of 39.4 cm 2 ·V - 1 ·s - 1 a turn-on voltage of -0.8 V and a low subthreshold swing of 0.47 V/decade. Cu diffusion is suppressed because pre-annealing can protect a-IGZO from damage during the electrode sputtering and reduce the copper diffusion paths by making film denser. Due to the interaction of Cr with a-IGZO, the carrier concentration of a-IGZO, which is responsible for high mobility, rises.

16.
Sci Rep ; 4: 7198, 2014 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-25425090

RESUMO

The effect of n-type interlayer in hybrid white organic light-emitting diodes (WOLEDs) has been systematically investigated by using various n-type materials. A new finding, that the triplet energy rather than electron mobility or hole-blocking ability of interlayer plays a more positive role in the performance of hybrid WOLEDs, is demonstrated. Based on the new finding, a more efficient n-type interlayer bis[2-(2-hydroxyphenyl)-pyridine] beryllium has been employed to realize a high-performance hybrid WOLED. The resulting device (without n-doping technology) exhibits low voltages (i.e., 2.8 V for 1 cd/m(2), 3.9 V for 100 cd/m(2)) and low efficiency roll-off (i.e., 11.5 cd/A at 100 cd/m(2) and 11.2 cd/A at 1000 cd/m(2)). At the display-relevant luminance of 100 cd/m(2), a total power efficiency of 16.0 lm/W, a color rendering index of 73 and an extremely long lifetime of 12596265 h are obtained. Such superior results not only comprehensively indicate that the n-type materials are effective interlayers to develop high-performance hybrid WOLEDs but also demonstrate a significant step towards real commercialization in WOLEDs.

17.
Adv Mater ; 26(16): 2586-91, 2014 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-24488944

RESUMO

Absorption spectra of polymer FBT-Th4 (1,4) (M n = 46.4 Kg/mol, E g = 1.62 eV, and HOMO = -5.36 eV) indicate strong interchain aggregation ability. High hole mobilities up to 1.92 cm(2) (V s)(-1) are demonstrated in OFETs fabricated under mild conditions. Inverted solar cells with active layer thicknesses ranging from 100 to 440 nm display PCEs exceeding 6.5%, with the highest efficiency of 7.64% achieved with a 230 nm thick active layer.

18.
Nanomicro Lett ; 6(4): 335-339, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-30464944

RESUMO

A very-high color rendering index white organic light-emitting diode (WOLED) based on a simple structure was successfully fabricated. The optimized device exhibits a maximum total efficiency of 13.1 and 5.4 lm/W at 1,000 cd/m2. A peak color rendering index of 90 and a relatively stable color during a wide range of luminance were obtained. In addition, it was demonstrated that the 4,4',4″-tri(9-carbazoyl) triphenylamine host influenced strongly the performance of this WOLED. These results may be beneficial to the design of both material and device architecture for high-performance WOLED.

19.
Nanotechnology ; 19(35): 355201, 2008 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-21828834

RESUMO

Trigonal Se nanowires (NWs) were fabricated through a high-yield chemical solution process. The morphology and structural characterization of the Se NWs were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and x-ray diffraction (XRD). The results indicated that the Se NWs grow along the crystallographic c-axis, the direction of which is parallel to the helical chains of Se atoms. Single Se NW field effect transistor (FET) devices were prepared through photolithographic patterning. The device performance shows that the Se NWs are p-type semiconductors displaying mobility up to 30 cm(2) V(-1) s(-1). This finding on the Se NW FETs has broad implications and provides very useful fundamental information necessary for future applications in the fabrication of high-quality NW FETs and other electronic devices.

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