透明叠层结构Ag/MoO_3/Ag阳极对绿光OLED器件性能的影响

本文采用一种结构为Ag/MoO_3/Ag的金属/氧化物/金属(M_1/O/M_2)叠层替代ITO作为OLED器件的阳极,研究Ag/MoO_3/Ag叠层结构变化对于OLED器件电极透过率、亮度、光谱等性能的影响。实验采用真空蒸镀方法制备了一系列器件,器件结构为Ag/MoO_3/Ag/MoO_3(10nm)/NPB(40nm)/Alq_3(60nm)/LiF(1nm)/Al(150nm)。对比器件的电压-电流密度、电压-亮度、光谱特性等数据,表明Ag/MoO_3/Ag的结构为20/20/10(nm)时,器件性能较好。在驱动电压为11V时,其亮度达到18 421cd/m~2,电流效率为2.45cd/A;且因器件中存在微腔效应,其EL光谱蓝移,半高宽变窄。但考虑到530nm处其电极透过率仅为17%,所以经换算该器件实际发光亮度比ITO电极器件更高。该Ag/MoO_3/Ag叠层阳极制作相对简单,经优化后在顶发射和柔性OLED器件方面将具有一定的应用前景。     

Organic thin-film field-effect transistors with MoO3/Al electrode and OTS/SiO2 bilayer gate insulator

An organic thin-film transistor (OTFTs) having OTS/SiO₂ bilayer gate insulator and MoO₃/Al electrode configuration between gate insulator and source–drain (S–D) electrodes has been investigated. Thermally grown SiO₂ layer is used as the OTFT gate dielectric and copper phthalocyanine (CuPc) for an active layer. We have found that using silane coupling agents, octadecyltrichlorosilane (OTS) on SiO₂, surface energy of SiO₂ gate dielectric is reduced; consequently, the device performance has been improved significantly. This OTS/SiO₂ bilayer gate insulator configuration increases the field-effect mobility, reduces the threshold voltage and improves the on/off ratios simultaneously. The device with MoO₃/Al electrode has similar source–drain current (I_DS) compared to the device with Au electrode at same gate voltage. Our results indicate that using double-layer of insulator and modified electrode is an effective way to improve OTFT performance.     

High efficiency polycrystalline silicon solar cells using lowtemperature PECVD process

Conventionally directionally solidified (DS) and silicon film (SF) polycrystalline silicon solar cells are fabricated using gettering and low temperature plasma enhanced chemical vapor deposition (PECVD) passivation. Thin layer (~10 nm) of PECVD SiO₂ is used to passivate the emitter of the solar cell, while direct hydrogen rf plasma and PECVD silicon nitride (Si₃N₄) are implemented to provide emitter and bulk passivation. It is found in this work that hydrogen rf plasma can significantly improve the solar cell blue and long wavelength responses when it is performed through a thin layer of PECVD Si₃N₄. High efficiency DS and SF polycrystalline silicon solar cells have been achieved using a simple solar cell process with uniform emitter, Al/POCl₃ gettering, hydrogen rf plasma/PECVD Si₃N₄ and PECVD SiO₂ passivation. On the other hand, a comprehensive experimental study of the characteristics of the PECVD Si₃N₄ layer and its role in improving the efficiency of polycrystalline silicon solar cells is carried out in this paper. For the polycrystalline silicon used in this investigation, it is found that the PECVD Si₃N₄ layer doesn't provide a sufficient cap for the out diffusion of hydrogen at temperatures higher than 500°C. Low temperature (⩽400°C) annealing of the PECVD Si₃N ₄ provides efficient hydrogen bulk passivation, while higher temperature annealing relaxes the deposition induced stress and improves mainly the short wavelength (blue) response of the solar cells     

Bphen掺杂Cs_2CO_3作为电子传输层对OLED器件性能的影响

为改善OLED器件的载子注入平衡,本文在其结构ITO/MoO3/NPB/Alq3/Cs2CO3/Al中,分别引入高电子迁移率材料Bphen及Bphen∶Cs2CO3作为电子传输层。通过改变Bphen的厚度以及Bphen中Cs2CO3的体积掺杂浓度,研究其对器件发光亮度、电流密度和效率等性能的影响。实验结果表明,采用Bphen或者Bphen∶Cs2CO3作为电子传输层,均能提高器件的电子注入能力,改善器件的性能。相比于未引入Bphen的器件,采用25nm的Bphen作为电子传输层,改善了器件的电子注入,使器件的最大电流效率提高112%;采用体积掺杂浓度为15%,厚度为5nm的Bphen∶Cs2CO3作为电子传输层,减小了电子注入势垒,使器件的最大电流效率提高27%,并且掺杂层厚度的改变对器件的电子注入影响很小。该方法可用于OLED器件的阴极修饰,对器件性能的提升将起到一定的促进作用。     

95%Al2O3陶瓷的MoO3体系低温金属化机理研究

本文采用由MoO₃加活化剂组成的配方对氧化铝陶瓷进行低温金属化,通过对氧化铝陶瓷、金属化层的显微结构及元素的分布情况来探索氧化铝陶瓷的低温金属化机理。研究发现金属化层中大部分MoO₃还原成活性较好的Mo颗粒,Mo颗粒间相互烧结连通为主体金属海绵骨架,同时少量的Mo氧化物与MnO、Al₂O₃、SiO 2、CaO等形成玻璃熔体,MnO、Al₂O₃、SiO 2、CaO之间也会形成MnO-Al₂O₃-SiO₂-CaO系玻璃熔体,从而获得致密、Mo金属与玻璃熔体相互缠绕、包裹的金属化层。金属化层中的两种玻璃熔体先后渗透、扩散进入氧化铝陶瓷晶界从而实现陶瓷与金属化层之间的连接。金属化层中还原的Mo金属与Ni层之间形成Mo-Ni合金,从而实现Ni层与金属化层之间的结合。     

利用CsN3n型掺杂电子传输层改善OLED器件性能的研究

为了能够有效地提高电子的注入和传输能力,改善有机电致发光器件的性能,本文利用CsN₃作为n型掺杂剂,对有机电子传输材料Bphen进行n型电学掺杂,制备了结构为ITO/MoO₃（2 nm）/NPB（50 nm）/Alq₃（30 nm）/Bphen（15 nm）/Bphen：CsN₃（15 nm,x%,x=10,15,20）/Al（100 nm）的器件。实验结果表明,CsN₃是一种有效的n型掺杂剂,以掺杂层Bphen：CsN₃ 作为电子传输层,可以有效地降低电子的注入势垒,改善器件的电子注入和传输能力,从而降低器件的开启电压,同时提高了器件的亮度和发光效率。在掺杂浓度为10%时器件的性能最优,开启电压仅为2.3 V,在7.2 V的驱动电压下,达到最大亮度29 060 cd/m²,是非掺杂器件的2.5倍以上。当驱动电压为6.6 V时,达到最大电流效率3.27 cd/A。而当掺杂浓度进一步提高时,由于Cs扩散严重,发光区形成淬灭中心,造成器件的效率下降。     

Efficiency improvement of polymer solar cells with random micro-nanostructured back electrode formed by active layer self-aggregation

The formation of a micro-nanostructured back electrode provides an efficient route for enhancing light absorption in polymer solar cells by light scattering of the bumpy electrode. In this study, we incorporated propylene glycol mono-methyl ether acetate (PGMEA) into the poly (3-hexylthiophene) (P3HT) and [6:6]-phenyl-C61-butyric acid (PC₆₁BM) solution, and the PGMEA induced P3HT aggregations give rise to a bumpy surface of the active layer. The sequential deposition of the Al electrode onto the active layer creates a polymer solar cell with interpenetrated micro-nanostructured morphology of the active layer/electrode interface. The higher crystallinity of P3HT induced by active layer self-aggregation improves carrier mobility. The bumpy active layer/electrode interface can not only facilitate charge carriers transfer and collection in the device, but also enhance optical scattering and leads to enhanced light absorption of the active layer. The resulting device shows improved photocurrent, corresponding to power conversion efficiency improvement of 17.9% as compared to the planar device. This work indicates that the active layer self-aggregation is a simple, cost-effective and mold-free methodology to manufacture high performance polymer solar cells with the micro-nanostructured back electrode.     

Quantum well model of a conjugated polymer heterostructure solar cell

In current study we analyzed the performance of a conjugated polymer heterostructured solar cell using quantum well representation for 100 Å thin polymer layers. The electrical field across the polymer layer is extremely strong to dissociate all excitons generated by sunlight. The behavior of free electrons appearing as a result of exciton dissociation was analyzed using wavefunctions and set of available energy levels. We came to the conclusion that small but finite probability exists to collect free electrons by the anode of the solar cell. The analyzed device was comprised of layers of bulk heterojunctions, namely, 100 nm layers of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1-4-phenylene vinylene]:phenyl C61-butyric acid methylester MDMO-PPV:PCBM (1:4), (poly-3-hexylthiophene): phenyl C61-butyric acid methylester P3HT:PCBM (1:1) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopen[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] PCPDTBT:PCBM (1:3). Set of these layers are designed to be connected using transparent cathodes of lithium fluoride/aluminium/gold LiF/Al/Au, which are compatible with PCBM LUMO.     

High mobility tri-layer a-Si:H thin-film transistors with ultrathinactive layer

We show that hydrogenated amorphous silicon thin-film transistors (a-Si:H TFT's) with active layer thickness of 13 nm perform better for display applications than devices with thicker 50-nm active layers. A direct comparison of a-Si:H TFT's fabricated using an i-stopper TFT structure shows that ultrathin active layers significantly improve the device characteristics. For a 5-μm channel length TFT, the linear region (V_DS=0.1 V) and saturation region mobilities increase from 0.4 cm²/V·s and 0.7 cm²/V·s for a 50-nm thick active layer a-Si:H device to 0.7 cm²/V·s and 1.2 cm²/V·s for a 13-nm thick active layer a-Si:H layer device fabricated with otherwise identical geometry and processing     

Effects of plasma etching chemistry and post-processing on themechanical adhesion and electrical contact of double polysilicon layerstructures

Double polysilicon layer structures separated by a silicon nitride layer are frequently used as structural multilayers in surface micromachining. In this paper the effect of three types of plasma etching chemistries for nitride patterning and post-processing on the characteristics of both mechanical adhesion and electrical contact resistance between the two polysilicon layers is investigated. It was found that all three chemistries yielded good mechanical adhesion between the two polysilicon layers. Both the chemistry based on CF₄ /SF₆, with a poor selectivity (0.7) of etching nitride over the underlying polysilicon layer, and the chemistry based on CHF ₃/CF₄, with a selectivity of 3, provided good electrical contact. The chemistry based on CHF₃/N₂, which yielded a selectivity of 15, on the other hand, resulted in a polymer film between the two polysilicon layers, resulting in electrical insulation. This polymer film can be effectively removed by using post-processing, which involves in-situ oxygen plasma treatment. Therefore, a chemistry such as that based on CHF₃/CF₄ can be applied when the lower polysilicon thickness allows a moderate selectivity, whereas the CHF₃/N ₂ chemistry is favored when high-selectivity is required. The latter, however, requires in-situ post-processing     

Ambient Layer‐by‐Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in flexible devices. Here, a layer‐by‐layer (LbL) protocol is reported as a facile, room‐temperature, solution‐processed method to prepare electron transport layers from commercial ZnO nanoparticles and polyacrylic acid (PAA) with a controlled and tunable porous structure, which provides large interfacial contacts with the active layer. Applying the LbL approach to bulk heterojunction polymer solar cells with an optimized ZnO layer thickness of ≈25 nm yields solar cell power‐conversion efficiencies (PCEs) of ≈6%, exceeding the efficiency of amorphous ZnO interlayers formed by conventional sputtering methods. Interestingly, annealing the ZnO/PAA interlayers in nitrogen and air environments in the range of 60–300 °C reduces the device PCEs by almost 20% to 50%, indicating the importance of conformational changes inherent to the PAA polymer in the LbL‐deposited films to solar cell performance. This protocol suggests a new fabrication method for solution‐processed polymer solar cell devices that does not require postprocessing thermal annealing treatments and that is applicable to flexible devices printed on plastic substrates.     

High-efficiency cadmium-free Cu(In,Ga)Se2 thin-filmsolar cells with chemically deposited ZnS buffer layers

Cadmium-free Cu(In,Ga)Se₂ (CICS) thin-film solar cells with a MgF₂/ZnO:Al/CBD-ZnS/CIGS/Mo/SLG structure have been fabricated using chemical bath deposition (CBD)-ZnS buffer layers and high-quality CICS absorber layers grown using molecular beam epitaxy (MBE) system. The use of CBD-ZnS, which is a wider band gap material than CBD-CdS, improved the quantum efficiency of fabricated cells at short wavelengths, leading to an increase in the short-circuit current. The best cell at present yielded an active area efficiency of 16.9% which is the highest value reported previously for Cd-free CIGS thin-film solar cells. The as-fabricated solar cells exhibited a reversible light-soaking effect under AM 1.5, 100 mW/cm² illumination. This paper also presents a discussion of the issues relating to the use of the CBD-ZnS buffer material for improving device performance     

Ligand‐Free Synthesis of Aluminum‐Doped Zinc Oxide Nanocrystals and their Use as Optical Spacers in Color‐Tuned Highly Efficient Organic Solar Cells

The color of polymer solar cells using an opaque electrode is given by the reflected light, which depends on the composition and thickness of each layer of the device. Metal‐oxide‐based optical spacers are intensively studied in polymer solar cells aiming to optimize the light absorption. However, the low conductivity of materials such as ZnO and TiO₂ limits the thickness of such optical spacers to tenths of nanometers. A novel synthesis route of cluster‐free Al‐doped ZnO (AZO) nanocrystals (NCs) is presented for solution processing of highly conductive layers without the need of temperature annealing, including thick optical spacers on top of polymer blends. The processing of 80 nm thick optical spacers based on AZO nanocrystal solutions on top of 200 nm thick polymer blend layer is demonstrated leading to improved photocurrent density of 17% compared to solar cells using standard active layers of 90 nm in combination with thin ZnO‐based optical spacers. These AZO NCs also open new opportunities for the processing of high‐efficiency color tuned solar cells. For the first time, it is shown that applying solution‐processed thick optical spacer with polymer blends of different thicknesses can process solar cells of similar efficiency over 7% but of different colors.     

Highly efficient ITO-free polymer solar cells based on metal resonant microcavity using WO3/Au/WO3 as transparent electrodes

Indium tin oxide (ITO)-free polymer solar cells (PSCs) with the structure of Glass/tungsten trioxide (WO₃)/Au/WO₃/PCDTBT: PC₇₀BM/LiF/Al was fabricated and studied. The multilayer structure of WO₃/Au/WO₃ is used as the potential transparent electrode to replace ITO. Metal resonant microcavity, which can enhance light harvesting of active layers, was constructed between Au and Al electrodes. According to the J–V and IPCE characterization with 70 nm active layer, power conversion efficiency (PCE) of the ITO-free microcavity device is approaching 4.55%, which is higher than that of the ITO-based device. However, PCE of the ITO-free device is much lower than that of the ITO-based device when the thickness of active layer increases to 130 nm. The opposite experimental tendency leads to theoretical research toward the simulation of light absorption and optical electric field and the calculation of maximum short circuit current density (J_{sc max}) as a function of active layer thickness based on ITO-free and ITO-based devices. The research results show that microcavity effect is closely linked to intrinsic absorption of active layers.     

17.3% efficiency metal-oxide-semiconductor (MOS) solar cells withliquid-phase-deposited silicon dioxide

Simple and high efficiency silicon metal-oxide semiconductor (MOS) solar cells, with silicon dioxide prepared by a room-temperature liquid phase deposition (LPD) method, are proposed. The thickness of LPD oxide is about 5 nm. After adding a 2~5 nm semi-transparent thin Al film between the 200 nm patterned Al cathode, all the solar cells' performance parameters are improved. For a cell exposed under 15 mW/cm ², short-circuit current density J_SC up to 10.7 mA/cm², open-circuit voltage V_OC up to 412 mV, fill factor FF up to 59, and record effective conversion efficiency η up to 17.3% are obtained for this structure. Photo-conductivity properties of LPD oxide are found and the mechanism is discussed     

不同旋涂速率对聚合物太阳电池性能的影响

以聚3己基噻吩(P3HT)和[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)为活性层材料制成聚合物太阳电池,通过控制活性层旋涂速率控制活性层厚度。从不同活性层厚度器件的吸收光谱、原子力及器件各项性能参数详细分析了不同活性层旋涂速率对太阳电池性能的影响。结果表明:旋涂速率为1 000 r/min时,电池具有最佳性能,光电转换效率最高为1.54%。     

Improved design of magnetooptic rib waveguides for opticalisolators

Garnet films of the following compositions (Lu,Bi)₃(Fe,Ga,Al)₅O₁₂ and (Tm,Bi)₃(Fe,Ga)₅O₁₂ are grown by liquid-phase epitaxy on [111]-oriented substrates of gadolinium gallium garnet. Double layers with opposite signs of Faraday rotation and single layers are prepared. Optical monomode rib waveguides are realized using such films. The nonreciprocal phase shift of the fundamental TM-mode is studied both theoretically and experimentally at a wavelength of 1.3 μm. The maximum nonreciprocal effect of double layer films is about 1.7 times larger than that of similar single layer waveguides. Agreement between experiments and calculations is excellent     

AlInGaAs-AlGaAs strained single-quantum-well diode lasers

Diode lasers with a strained AlInGaAs active layer and AlGaAs confining and cladding layers are reported. Broad-stripe devices were fabricated in graded-index separate-confinement heterostructures grown by organometallic vapor-phase epitaxy on GaAs substrates and containing a single Al_yIn_xGa_1-x-yAs quantum well with 0.12⩽x⩽0.14 and five values of y between 0.05 and 0.17. With increasing Al content the emission wavelength decreases from 890 to 785 nm. The threshold current density J _th is less than 200 A-cm^-2, with one exception, and the differential quantum efficiency ranges from 78 to 81%. A preliminary reliability test was made on a saw-cut, uncoated broad-area device, with an Al_0.17In_0.12Ga_0.71As active layer, that was fabricated without using special precautions to minimize damage and was mounted junction side up. After 20 h of CW operations at a constant current of 1.125 times threshold, J _th has increased by only 3.5%     

Visible light emitting Si/SiO2 superlattices

Six-period superlattices of Si/SiO₂ have been grown at room temperature using molecular beam epitaxy. With this mature technology, the ultra-thin (1–3 nm) Si layers were grown to atomic layer precision. These layers were separated by 1 nm thick SiO₂ layers whose thickness was also well controlled by using a rate-limited oxidation process. The chemical and physical structures of the multilayers were characterized by cross-sectional TEM, X-ray diffraction, Raman spectroscopy, Auger sputter-profile, and X-ray photoelectron spectroscopy. The analysis showed that the Si layer is free of impurities and is amorphous, and that the SiO₂/Si interface is sharp (0.5 nm). Photoluminescence (PL) measurements were made at room temperature using 457.9 nm excitation. The PL peak occurred at wavelengths across the visible range for these multilayers. The peak energy position E was found to be related to the Si layer thickness d by E (eV) = 1.60+0.72d⁻² in accordance with a quantum confinement mechanism and the bulk amorphous-Si band gap.     

Ge-laminated polarizer for 790-850-nm applications with extinctionratios larger than 50 dB and insertion losses below 0.4 dB

A laminated structure composed of alternating layers of Ge and SiO ₂ (Ge-LAMIPOL) is usable as a miniaturized polarizer at 790-850 nm in fiber optic gyroscopes, for instance. However, peeling of the sputter deposited layers, due to the weak binding strength between Ge and SiO₂, is a serious problem during the slicing process in preparation for assembly in the fiber. In order to improve the adhesive strength, the 1-nm-thick Si layers are inserted between Ge and SiO₂ layers. The Si layer functions as the adhesive layer via the Si-O bonding formation in place of the weaker Ge-O bond. The new Ge-LAMIPOL, including 125 layers of (1-nm Si)/(4.5-nm Ge)/(1-nm Si)/ (800-nm SiO₂) is successfully prepared without any fracture. The extinction ratio and the insertion loss were 51 and 0.33 dB at 850 nm, respectively, corresponding to 59.6 and 0.36 dB as the designed values