基于PIN结构的Rubrene/C_(70)太阳能电池的性能研究

实验制备了ITO/V2O5/Rubrene/C70:Rubrene/C70/BCP/Al的PIN结构有机太阳能电池(OSC),其中Rubrene、Rubrene:C70和C70分别作为P、I和N层。通过改变I层厚度,研究了I层对OSC性能的影响及作用机理。实验显示,I层厚为5nm时器件的功率转换效率η达到最大值为1.580%,同时获得了较大的短路电流密度Jsc为4.365mA·cm-2;相对PN结构器件,功率转化效率η短路电流密度Jsc和填充因子FF分别提高了40.3%、29.7%和8.2%。我们认为,I层中激子分离效率的提高导致了器件性能的改善。     

Bathocuproine作为缓冲层改善Rubrene/C70太阳能电池的性能

制备了结构为ITO/Rubrene/C70/BCP/Al的双层有机太阳能电池(OSCs),通过优化缓冲层BCP的厚度研究了BCP对OSCs性能的影响及其作用机理。实验发现,BCP厚为6nm时,器件的效率最高达到1.78%,同时获得了较大的开路电压0.901V。相对于没有缓冲层,器件的效率、短路电流、开路电压和填充因子分别提高了432.9%、74.8%、95.4%和55.5%。     

基于PIN结构的Rubrene/C70太阳能电池的性能研究

实验制备了ITO/V₂O₅/Rubrene/C₇₀:Rub rene/C₇₀/BCP/Al的PIN结构有机太阳能电池(OSC),其中 Rubrene、Rubrene:C₇₀和C₇₀分别作为P、I和N层。通过改变I层厚度,研究了I 层对OSC性能的影响及作用机理。实验显示,I层厚为5nm时器件的功率转换效率η达到最大值为1.580%,同时 获得了较大的短路电流密度Jsc为4.365mA· cm－2;相对PN结构器件,功率转化效率η短路电流密度Jsc和填充因子FF分别提 高了40.3%、29.7%和8.2%。我们认为,I层中激子分离效率的提高导 致了器件性能的改善。     

正置倒置异质结有机小分子太阳能电池

以MoO3为阳极修饰层,以Rubrene/C60为活性层,制备了正置和倒置异质结有机小分子太阳能电池。实验结果表明倒置器件的开路电压Voc、短路电流密度Jsc、填充因子FF和功率转换效率η比正置结构的器件分别提高了34%、20%、25%和102%。当插入BCP阴极缓冲层后,阻挡了热的Al原子对C60层的破坏,对倒置器件的性能没有明显的影响,但却显著改善了正置器件的性能,并分析了MoO3和BCP对倒置和正置器件的作用。     

基于MoO3和Re-Bphen修饰有机太阳能电池性能的研究

有机太阳能电池(OSCs)的性能与材料及器件结构密切相关。以MoO3为阳极缓冲层,有机金属配合物Re-Bphen为阴极缓冲层,制备了结构为ITO/MoO3/CuPc/C60/Re-Bphen/Al的OSCs。在标准太阳光照条件下,当MoO3和Re-Bphen的厚分别为5nm和8nm时实现了器件的最佳性能,能量转换效率(PCE)和器件寿命均显著提高。结合器件结构,分析了工作机制。     

双阴极修饰层改善Rubrene/C70有机太阳能电池的性能

采用NTCDA/PTCBI双阴极修饰层制备了结构为ITO /MoO₃/Rubrene/C70/NTCDA/PTCBI/Al有机太阳能 电池(OSC),研究了双阴极修饰层对Rubrene/C70 OSC性能的影 响。实验结果表明,引入双阴极修饰层 后,器件的各性能参数有了显著提高。通过对PTCBI厚度优化发现,当PTCBI厚为5nm时器件 的各性 能参数最佳,器件的功率转换效率(PCE)=3.19%,电流密度Jsc=8.99mA·cm－2,开路电 压Voc=0.85V, 填充因子(FF)=41.58%,与未插入PTCBI 层相比器件的各性能分别提高了538%、338.5% 、13.3%和16.5%。     

WO3对Rubrene/C70有机太阳能电池性能的改善

研究了WO₃对Rubrene/C₇₀有机太阳能电池 (OSCs)性能的 改善,制备了结构为ITO/WO₃/Rubrene/C₇₀/BCP/Al的OSCs,其中WO₃插入在I TO和Rubrene中间作为阳极修饰层。通过优化WO₃的厚度,研究了WO₃对OSCs性能的改善及其作用机理。实验发现,器件的短路电流Jsc、开路电压V_oc、 填充因子(FF)、光电转换效率(PCE)和串联电阻Rs等性能参数随WO₃厚度的变化呈规律性变化;当 WO₃厚度小于80 nm时,器件PCE随着厚度的增加不断增大;当W O ₃厚大于80 nm时,器件PCE随着厚度的 增加不断减小;当WO₃厚度为80 nm 时,器件PCE达到最高为1.03%, 相应的J sc、V_oc、FF分别为2.81mA·cm－2、 0.83V、43.85%,Rs为45.3Ω·cm²,对比没有WO₃修饰层, 器件的J_sc、V_oc、FF和PCE分别提高了31%、137%、17%,Rs降低了33%。     

利用C-545T超薄层多层结构的白光器件

为了探讨(3-545T超薄层的发光特性,设计了结构为:ITO/2T-NATA(20 nm)/NPBX(20 nm)/C-545T(d nm)/BCP(8 nm)./Alq(40 nm)/LiF(0.5 nm)/Al的绿光器件.结果表明,随着C-545T层厚度d的增加,器件的亮度和效率均下降,这是由于C-545T染料的浓度淬灭效应引起的.在此基础上,制备了基于C-545T超薄层为发光层之一的多层结构的白光器件,器件结构为:ITO/NPBX(30 nm)/Rubrene(0.2 nm)/NPBX(5 nm)/DPVBi (20 nm)/NPBX(4 nm)/C-545T(0.1 nm)/Alq(30 nm)/LiF(0.5 nm)/Al.在驱动电压为16 V时,其最大亮度达到12 320 cd/m2,对应的色坐标为(0.32,0.40),在电压为4 V时,最大光功率效率达到了3.45 lm/w.     

MoO3作空穴注入层的绿光有机电致发光器件制备及其性能研究

用真空热蒸镀的方法制备了绿光有机电致发光器件,并对其工艺流程进行了详细的描述。器件结构为ITO/MoO3(xnm)/N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,18-biphenyl)-4,4-diamine(NPB)(40nm)/tris(8-hydroxyquinoline)aluminum(Alq3)(60nm)/LiF(1nm)/Al(150nm),其中x=0,5nm。实验中,对ITO基片进行氧等离子体表面处理,能够有效减小ITO表面的接触角。通过对器件的光电性能测试,研究了MoO3作空穴注入层对有机电致发光器件性能的影响。实验结果表明,空穴注入层MoO3的最高占据分子轨道(HOMO)能级较好的与ITO功函数匹配,降低了空穴注入势垒,提高了器件的发光亮度和效率。当外加电压小于10V时,器件的电流密度随外加电压的增加而增加,但变化不明显;当外加电压大于10V时,器件的电流密度明显增强,发光色度几乎不随驱动电压的改变而改变,色坐标稳定在(0.36,0.55)附近。     

Optimization and degradation of rubrene/C70 heterojunction solar cells

Small molecule organic solar cells (OSCs) with the structure of indium tin oxide (ITO)/molybdenum trioxide (MoO3) (5 nm)/rubrene (x nm)/fullerene (C70) (y nm)/2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (BCP) (6 nm)/aluminum (Al) (150 nm) are fabricated. The thickness of active layer for the devices is investigated in details. The results show that the optimum thicknesses of rubrene layer and C70 layer are 30 nm and 25 nm, respectively. The degradation of the device is also investigated. The result indicates that the open-circuit voltage (Voc) does not change, while the short-circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) decrease continuously with time. The degradation can be attributed to the oxygen in ambient diffusing and infiltrating into the active materials and reacting with C70 in cells, which can result in the increase of interfacial series resistance.     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.