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1.
The doping effect on charge carrier mobility in tris (8-hydroxyquinolinato) aluminum (Alq3) was studied by time-of-flight (TOF) measurements. The polar dopant, coumarin 6 (C-6) and extensive π conjugated dopant, 5,6,11,12-tetraphenylnaphthacene (rubrene) were used for this study. The co-doped of rubrene (Rb) with C-6 into Alq3 improved the carrier mobility compared to the single doped Alq3:C-6 film. The carrier mobility in single doped Alq3:C-6 film did not follow the linear relationship of Poole-Frenkel (PF) model with applied electric field. The mobility was in agreement with the PF model at two different ranges of electric fields (F) separated by a critical field . The mobility in co-doped Alq3:(Rb:C-6) film followed the linear relationship with the PF model. The energetic disorder was found as ∼0.32 eV in co-doped films. It was ∼0.55 and ∼0.27 eV before and after the critical field in Alq3:C-6 film. The values of positional disorders in co-doped films were estimated as ∼1.8 and it was ∼2 in Alq3:C-6 film at . The organic light emitting diode performance of the co-doped film was improved compared to single doped film. The luminescence efficiency was improved tremendously to ∼6 Cd/A in co-doped device at 45 mA/cm2 current compared to Alq3:C-6 film device of ∼1 Cd/A. 相似文献
2.
利用飞行时间法(time-of-flight)测定了有机小分子发光材料8-羟基喹啉铝(Alq3)与CdSeS量子点掺杂体系的载流子迁移率.研究了Alq3和CdSeS混合薄膜的载流子迁移率与外加电场强度和量子点浓度的变化关系.研究结果表明,CdSeS量子点的掺杂浓度的增加会引起薄膜样品位置无序的增加.除此之外,Alq3和CdSeS量子点界面之间的电荷转移作用,以及在量子点之间进行跳跃传输的电子数量都会改变样品的载流子迁移率.
关键词:
3')" href="#">Alq3
CdSeS量子点
飞行时间法 相似文献
3.
Photorefractive properties of highly-doped lithium niobate crystals in the visible and near-infrared 总被引:5,自引:0,他引:5
Light-induced refractive-index changes, bulk-photovoltaic current densities, and photoconductivities of photorefractive iron-doped
lithium niobate crystals (iron concentrations between 0.02 and 0.17 wt. %) are investigated in detail using visible and near-infrared
light. It turns out that the one-center model predicts the material performance correctly for small iron concentrations (cFe<0.06 wt. % Fe2O3), only. A strong increase of the photoconductivity for higher doping levels limits the space-charge fields. Refractive-index
changes up to 7×10-4 for green and 2.8×10-4 for near-infrared ordinarily polarized light are obtained. The corresponding hologram multiplexing numbers are 11 for green
and 5 for near-infrared light.
Received: 18 November 1998 / Revised version: 8 January 1999 / Published online: 7 April 1999 相似文献
4.
R. Kumaravel S. Bhuvaneswari K. Ramamurthi V. Krishnakumar 《Applied Physics A: Materials Science & Processing》2012,109(3):579-584
Molybdenum-doped cadmium oxide films were prepared by a spray pyrolysis technique at a substrate temperature of 300?°C. The effect of doping on structural, electrical and optical properties were studied. X-ray analysis shows that the undoped CdO films are preferentially oriented along the (111) crystallographic direction. Molybdenum doping concentration increases the films?? packing density and reorients the crystallites along the (200) plane. A?minimum resistivity of 4.68×10?4????cm with a maximum mobility of 75?cm2?V?1?s?1 is achieved when the CdO film is doped with 0.5?wt.% Mo. The band-gap value is found to increase with doping and reaches a maximum of 2.56?eV for 0.75?wt.% as compared to undoped films of 2.2?eV. 相似文献
5.
X. Hao J. Ma D. Zhang X. Xu Y. Yang H. Ma S. Ai 《Applied Physics A: Materials Science & Processing》2002,75(3):397-399
Transparent conducting antimony-doped tin oxide (SnO2:Sb) films were deposited on organic substrates by r.f. magnetron-sputtering. Polycrystalline films with a resistivity of
≈ 6.5×10-3 Ω cm, a carrier concentration of≈ 1.2×1020 cm-3 and a Hall mobility of ≈ 9.7 cm2 v-1 s-1 were obtained. The average transmittance of these films reached 85% in the wavelength range of the visible spectrum.
Received: 20 April 2001 / Accepted: 23 July 2001 / Published online: 17 October 2001 相似文献
6.
We have investigated the emission properties of dopants 5,6,11,12-tetraphenylnapthacene (rubrene) and 3-(2′-benzothiazolyl)-7-diethylaminocoumarin (coumarin 6) as well as co-doping of these two dopants in tris (8-hydroxyquinolinato) aluminum (Alq3) films in double-layer organic light emitting diodes (OLEDs). We varied the rubrene (Rb) doping concentration in Alq3:Rb films up to 10 wt%. The maximum luminescence efficiency of ∼6.5 cd/A was observed for Rb doping concentration of ∼0.7 wt% in Alq3:Rb film, which was nearly double efficiency compared to pure Alq3 device. The co-doping of dopants of C-6 and Rb in the ratio of 1:1 and 1:2 in Alq3 films reduced the bias voltage compared to pure Alq3 and Alq3:C-6 devices for the same current density. The maximum luminescence efficiency was improved to ∼7 cd/A in Alq3:{C-6:Rb(1:2)} film OLED. The direct recombination of holes and electrons in the dopant molecules may be responsible for the improvement of the luminescence efficiency. We also observed the shifting of photoluminescence (PL) and electroluminescence (EL) peaks position from ∼515 to ∼562 nm by co-doping of Rb and C-6 in Alq3. 相似文献
7.
8.
Tris-(8-hydroxyquinoline)aluminum (Alq3) thin films, the most widely used electron transport/emissive material in the organic electroluminescent (EL) devices, have been deposited on glass substrates by thermal evaporation process. Alq3 thin films were exposed to light for various time periods under normal ambient. The fluorescence of as-prepared and light exposed Alq3 thin films and formation of luminescent quencher have been studied using fluorescence, Mass, MALDI-ToF-MS, 1H & 13C NMR, and FT-IR spectroscopy. It is observed that among the three 8-hydroxyquinoline (HQ) units in Alq3 molecule, one HQ unit is affected during the light exposure in the normal ambient. It is found that the affected resultant Alq3 molecule containing the carbonyl group acts as fluorescent quencher and the energy of excitons in the Alq3 molecule in the light exposed Alq3 thin films can be non-radiatively transferred to the neighboring fluorescent quencher, quenching the fluorescence of light exposed Alq3 thin films in the normal ambient. 相似文献
9.
Production and characterization of Nd,Cr:GSGG thin films on Si(001) grown by pulsed laser ablation 总被引:2,自引:0,他引:2
P.R. Willmott P. Manoravi K. Holliday 《Applied Physics A: Materials Science & Processing》2000,70(4):425-429
Nd,Cr:Gd3Sc2Ga3O12 (GSGG) thin films have been produced for the first time. They were grown on Si(001) substrates at 650 °C by pulsed laser
ablation at 248 nm of a crystalline Nd,Cr:GSGG target rod. The laser plume was analyzed using time-of-flight quadrupole mass
spectroscopy, and consisted of elemental and metal oxide fragments with kinetic energies typically in the range 10 to 40 eV,
though extending up to 100 eV. Although films deposited in vacuum using laser fluences of 0.8±0.1 J cm−2 reproduced the Nd,Cr:GSGG bulk stoichiometry, those deposited using fluences above ≈3 J cm−2 resulted in noncongruent material transfer and were deficient in Ga and Cr. Attempts to grow films using synchronized oxygen
or oxygen/argon pulses yielded mixed oxide phases. Under optimal growth conditions, the films were heteroepitaxial, with GSGG(001)[100]∥Si(001)[100],
and exhibited Volmer–Weber-type growth. Room-temperature emission spectra of the films suggest efficient non-radiative energy
transfer between Cr3+ and Nd3+ ions, similar to that of the bulk crystal.
Received: 1 October 1999 / Accepted: 15 October 1999 / Published online: 23 February 2000 相似文献
10.
材料的迁移率是其关键电学特性之一.有机材料迁移率的研究对于有机电致发光器件、 有机太阳电池、有机薄膜场效应晶体管性能的提高有重要的意义. 应用简单易行的空间电荷限制电流方法,对基于三(8-羟基喹啉)铝(Alq3) 的四种单载流子器件电流密度-电压曲线特性进行研究, 根据空间电荷限制电流模型,拟合出Alq3材料在四种器件中的零场电子迁移率和电场依赖因子,并且给出Alq3电子迁移率随外加偏压的变化趋势. 实验结果表明,顶电极铝蒸镀到缓冲层氟化锂(1 nm)和Alq3 (100 nm)的表面后, 可以明显改善Alq3的零场迁移率和电场依赖因子. 认为产生这种现象的原因是氟化锂可以使铝和Alq3发生络合反应, 形成Li+1Alq-1粒子,形成良好的欧姆接触,使得电子的注入效率大大提高. 相似文献
11.
12.
Hsin‐Han Lee J. Hwang Tun‐Wen Pi Y.‐C. Wang W.‐J. Lin C.‐P. Cheng 《Journal of synchrotron radiation》2008,15(1):91-95
A series of Cs 4d and Al 2p spectra associated with valence‐band and cut‐off spectra have been used to characterize the interaction between caesium and tris(8‐hydroxyquinoline) aluminium (Alq3) molecules in a Cs‐doped Alq3 layer. The Cs 4d and Al 2p spectra were tuned to be very surface sensitive by selecting a photon energy of 120 eV at the National Synchrotron Radiation Research Center, Taiwan. A critical Cs concentration exists, above which a new Al 2p signal appears next to the Al 2p peak of Alq3 in the lower binding‐energy side. The Al 2p signal was analyzed and assigned as being contributed from a mixture of Alq2, Alq and Al. Experimental data supported the observation that bond cutting of Alq3 by the doped Cs atoms occurred at high Cs doping concentration. 相似文献
13.
Chan y Díaz E. Duarte-Moller A. Camacho Juan M. Castro-Rodríguez R. 《Applied Physics A: Materials Science & Processing》2012,106(3):619-624
SnO2 thin films have been deposited on glass substrates by pulsed Nd:YAG laser at different oxygen pressures, and the effects
of oxygen pressure on the physical properties of SnO2 films have been investigated. The films were deposited at substrate temperature of 500°C in oxygen partial pressure between
5.0 and 125 mTorr. The thin films deposited between 5.0 to 50 mTorr showed evidence of diffraction peaks, but increasing the
oxygen pressure up to 100 mTorr, three diffraction peaks (110), (101) and (211) were observed containing the SnO2 tetragonal structure. The electrical resistivity was very sensitive to the oxygen pressure. At 100 mTorr the films showed
electrical resistivity of 4×10−2 Ω cm, free carrier density of 1.03×1019 cm−3, mobility of 10.26 cm2 V−1 s−1 with average visible transmittance of ∼87%, and optical band gap of 3.6 eV. 相似文献
14.
R. Czaputa 《Applied Physics A: Materials Science & Processing》1989,49(4):431-436
Recent investigations on transition-metal impurities in silicon emphasizing the effect of the combined diffusion of two transition metals are presented and briefly discussed. The electronic properties and basic thermal kinetics are analysed by DLTS. The conversion of a Pd-related multivalent defect atE
c-0.35 eV andE
c-0.57 eV to the Pd-related defect atE
c –0.22 eV is observed, and a Pd-Fe complex level atE
c –0.32 eV is identified. The annealing characteristics of the multivalent Rh levels atE
c-0.33 eV andE
c-0.57 eV are observed, and used to analyse the influence of prior Rh doping on the Au diffusion. A complex formed by the codiffusion of Au and Cu is observed atE
v+0.32eV andE
v+0.42 eV, and shown to exhibit bistable behavior as does a similarly produced Au-Ni complex observed atE
v + 0.35 eV andE
v+0.48 eV. 相似文献
15.
16.
This paper describes the effect of doping on the composition, surface morphology and optical, structural and electrical properties of Al doped ZnO thin films by pulsed laser deposition. SEM analysis shows that the crystalline nature of the deposited films decreases with an increase of Al doping concentration from 1% to 6%. In the AFM analysis, the surface roughness of the deposited films increases by increasing the doping concentration of Al. Al doping strongly influences the optical properties of the ZnO thin films. Optical transmittance spectra show a very good transmittance in the visible region (450–700 nm). The calculated optical band gap was found to be in the range from 3.405 to 3.464 eV. Structural analysis confirms that the increases of Al concentration decrease the crystallinity of the ZnO films and the particle size decreases from 45.7±0.09 to 28.0±0.02 nm. In the Raman analysis, the active mode of Al(=1%) doped ZnO films were observed at 434.81 cm−1. The shifts of the active mode (E2) show the presence of tensile stress in the deposited films. The electrical properties of the deposited films showed that the values of the Hall mobility was in the range between 2.51 and 10.64 cm2/V s and the carrier concentration between 15.7 and 0.78×1017 and the resistivity values between 1.59 and 10.97 Ωcm, depending on the doping concentration. 相似文献
17.
Influence of small-molecule material on performance of polymer solar cells based on MEH-PPV:PCBM blend
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In this work,the influence of a small-molecule material,tris(8-hydroxyquinoline) aluminum (Alq 3),on bulk het-erojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C 61-butyric acid methyl ester (PCBM).By dop-ing Alq 3 into MEH-PPV:PCBM solution,the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq 3 to MEH-PPV,which probably induces the increase of photocurrent generated by excitons dissociation.However,the low carrier mobility of Alq 3 is detrimental to the efficient charge transport,thereby blocking the charge collection by the respective electrodes.The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs.For the case of 5 wt.% Alq 3 doping,the device performance is deteriorated rather than improved as compared with that of the undoped device.On the other hand,we adopt Alq 3 as a buffer layer instead of commonly used LiF.All the photovoltaic parameters are improved,yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer.Even for the 5 wt.% Alq 3 doped device,the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq 3.The performance deterioration of Alq 3-doped devices can be explained by the low solubility of Alq 3,which probably deteriorates the bicontinuous D-A network morphology;while the performance improvement of the devices with Alq 3 as a buffer layer is attributed to the increased light harvesting,as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq 3 compared with that of MEH-PPV. 相似文献
18.
We demonstrate n-type doping of pentacene with the powerful reducing molecule decamethylcobaltocene (CoCp2*). Characterization of pentacene films deposited in a background pressure of CoCp2* by X-ray photoemission spectroscopy and Rutherford backscattering confirm that the concentration of incorporated donor molecules
can be controlled to a level as high as 1%. Ultraviolet photoemission spectroscopy show Fermi level (E
F) shifts toward unoccupied pentacene states, indicative of an increase in the electron concentration. A 1% donor incorporation
level brings E
F to 0.6 eV below the pentacene lowest unoccupied molecular orbital. The corresponding electron density of ∼1018 cm−3 is confirmed by capacitance–voltage measurements on a metal–pentacene–oxide–silicon structure. The demonstration of n-doping
suggests applications of CoCp2* to pentacene contacts or channel regions of pentacene OTFTs. 相似文献
19.
The conducting polymer electrolyte films consisting of polyacrylonitrile (PAN) as the host polymer, lithium triflate (LiCF3SO3) and sodium triflate (NaCF3SO3) as inorganic salts were prepared by the solution-cast technique. The pure PAN film was prepared as a reference. The ionic
conductivity for the films is characterized using impedance spectroscopy. The room temperature conductivity for the PAN + 26 wt.%
LiCF3SO3 film and the PAN + 24 wt.% NaCF3SO3 film is 3.04 × 10−4 S cm−1 and 7.13 × 10−4 S cm−1, respectively. XRD studies show that the complexation that has occurred in the PAN containing salt films and complexes formed
are amorphous. The FTIR spectra results confirmed the complexation has taken place between the salt and the polymer. These
results correspond with surface morphology images obtained from SEM analysis. The conductivity–temperature dependence of the
highest conducting film from PAN + LiCF3SO3 and PAN + NaCF3SO3 systems follows Arrhenius equation in the temperature range of 303 to 353 K. The PAN containing 24 wt.% LiCF3SO3 film has a higher ionic conductivity and lower activation energy compared to the PAN containing 26 wt.%LiCF3SO3 film. These results can be explained based on the Lewis acidity of the alkali ions, i.e., the interaction between Li+ ion and the nitrogen atom of PAN is stronger than that of Na+ ion. 相似文献
20.
H. Lefèvre 《Applied Physics A: Materials Science & Processing》1980,22(1):15-22
Deep-level profiles were measured radially acrossn-type FZ silicon wafers containing A-swirl defects by applying DLTS to an array of Schottky contacts. The trapparameters were
obtained very accurately using a computer-fit procedure for the full DLTS peaks. Two acceptor levels atE
c
−0.49 eV (σ
n
=6.6×10−16cm2) andE
c
−0.07 eV (σ
n
=4.6×10−16cm2) were observed, which varied oppositely to the A-swirl defect density. At short ranges (1–2mm) the trap concentration-profile
was smeared out and did not follow the strong fluctuations in the etch pattern. Both levels were measured together with the
same concentration. The profiles indicate outdiffusion. A level atE
c
−0.14 eV (σ
n
=1.1×10−16cm2) was not related to A-swirl defects. A level atE
c
−0.11 eV (σ
n
=1.1×10−15cm2) was only detected in one ingot.
The properties of the deep level atE
c
−0.49 eV are discussed in the light of published DLTS results reported for γ-irradiation, laser annealing after self-implantation,
annealing under pressure and oxidation of silicon samples. It is concluded, that this level is related to interstitial silicon
rather than to an impurity. 相似文献