High efficiency nanotextured silicon solar cells

We report the computational modeling of forward scattering phenomena arising in Au nanoparticles array near their localized surface plasmon resonance, which by producing a strong field enhancement effect on the substrate leads to higher optical absorption and, therefore, higher efficiencies of operation. Computational calculations indicate that the ultimate efficiency of an optimized silicon nanoholes (SiNH) array texture surface in combination with the surface and bottom-of-a-trench Au nanoparticles array described herein, is 39.67%, which compares favorably with the ultimate efficiency of 31.11% for an optimized silicon nanoholes array texture surface. Furthermore, the utilization of an optimized silicon nitride antireflection coating increases the ultimate efficiency to a promising value of 41.88%, while the utilization of a single-crystal silicon layer of thickness 2.8 μm will be instrumental in drastically reducing solar cell manufacturing cost.     

Enhanced thermal stability of VCSEL array by thermoelectric analysis-based optimization of mesas distribution

The thermal stability of a vertical-cavity surface-emitting laser(VCSEL) array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional(3D) finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.     

L波段径向线螺旋阵列天线的优化设计

 以提高阵列天线的口径效率为目标,对辐射单元及阵列布局进行了优化,设计了中心频率为1.57 GHz的6元单圆环径向线螺旋阵列天线,采用时域有限积分算法软件对阵列天线进行了数值模拟,结果表明：口径为320 mm的该天线在中心频率上可获得14.4 dBi的增益,口径效率达99%,轴向轴比值为1.15,在1.5～1.7 GHz的频带范围内,增益大于13.9 dBi,口径效率大于97%,轴向轴比值小于1.35。     

电极结构对AlGaInP-LED阵列电流分布的影响

以AlGaInP-LED外延片为基片,设计了分辨率为320×240、像素尺寸为100 μm×100 μm的微型LED阵列。针对目前LED阵列普遍存在的电流分布不均匀的问题,建立了内部电流分布模型,研究了电极结构、电极尺寸及电极间距等不同因素对LED电流分布造成的影响。在单条形电极结构的基础上进行优化,综合考虑不透明电极的遮光效应等因素得到三条形电极结构为最优的电极结构,该电极结构的LED有源层均匀发光面积比未经优化的单条形电极提高了65.02%,比双条形电极提高25.63%,有效提高了微型LED阵列的出光效率,对改善LED芯片发光均匀性具有参考意义。     

一种新型的液闪阵列成像屏空间分辨特性

针对低强度射线成像,自主研制了一种像元为0.1 mm高探测效率的液闪阵列屏.为此,基于倾斜刀口边缘响应的测量原理,建立了理论模拟方法和实验研究方法,对该液闪阵列屏开展了空间分辨性能研究.通过理论模拟,给出了液闪阵列屏在14 MeV中子和1.25 MeV伽马射线激发下的调制传递函数,并与像元为0.1,0.3和0.5 mm的闪烁纤维阵列屏进行了理论对比.在60Co伽马射线源上,对液闪阵列屏和像元为0.3和0.5 mm的两种国产闪烁纤维阵列屏进行了调制传递函数实测研究.理论模拟和实验结果一致,均表明液闪阵列的空间特性优于闪烁纤维阵列屏,而且具有更好的均匀性,对1.25 MeV伽马,空间分辨接近0.9 lp/mm,而其他两种纤维阵列屏仅达到0.5 lp/mm,对于14 MeV中子,液闪阵列屏的空间分辨可达到1.8 lp/mm.     

基于纳米孔阵列增透膜的光伏器件特性分析及实验研究

利用严格耦合波理论分析了纳米孔阵列薄膜的光学特性,提出将纳米孔阵列薄膜作为光伏器件 增透膜来提高器件的光吸收和转换效率.理论分析表明:纳米孔阵列薄膜比单层增透膜有更好的增透效果, 能够更好地提高光伏器件的转换效率,在400 nm-600 nm波段尤为显著.纳米孔阵列薄膜的最优结构参数: 周期为500 nm,填充率为0.2,厚度为110 nm.采用微纳加工技术,在Φ 200 μm Si 探测器的增透膜上制作了不同周期的纳米孔阵列,并搭建了相应的测试系统.实验结果表明: 周期为500 nm时器件的性能提高最为明显,短路电流在400 nm-1100 nm波段提高约为6%, 在400 nm-600 nm波段提高约为15%;开路电压提高约为2%.纳米孔阵列薄膜能够很好地提高光伏器件 的转换效率.     

硅薄膜太阳电池表面纳米线阵列光学设计

陷光结构的优化是增加硅薄膜太阳电池光吸收进而提高其效率的关键技术之一. 以硅纳米线阵列为代表的光子晶体微纳陷光结构具有突破传统陷光结构Yablonovith极限的巨大潜力. 通常硅纳米线阵列可以用作太阳电池的增透减反层、轴向p-n结、径向p-n结. 针对以上三种应用, 本文运用有限时域差分(FDTD)法系统研究了硅纳米线阵列在 300-1100 nm 波段的光学特性. 结果表明, 当硅纳米线作为太阳电池的减反层时, 周期P=300 nm, 高度H=1.5 μm, 填充率(FR)为0.282条件下时, 反射率最低为7.9%. 当硅纳米线作为轴向p-n结电池时, P=500 nm, H=1.5 μm, FR=0.55条件下纳米线阵列的吸收效率高达22.3%. 硅纳米线作为径向p-n结电池时, 其光吸收主要依靠纳米线, 硅纳米线P=300 nm, H=6 μm, FR= 0.349 条件下其吸收效率高达32.4%, 进一步提高其高度吸收效率变化不再明显. 此外, 本文还分析了非周期性硅纳米线阵列的光学性质, 与周期性硅纳米线阵列相比, 直径随机分布和位置随机分布的硅纳米线阵列都可以使吸收效率进一步提高, 相比于周期性硅纳米线阵列, 优化后直径随机分布的硅纳米线阵列吸收效率提高了39%, 吸收效率为27.8%. 本文运用FDTD法对硅纳米线阵列的光学特性进行设计与优化, 为硅纳米线阵列在太阳电池中的应用提供了理论支持.     

Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

Hybrid near-field acoustical holography(NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH,we combine statistically optimized near-field acoustical holography(SONAH) and broadband acoustical holography from intensity measurements(BAHIM) to reconstruct the underwater cylindrical source field. First,the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary,and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal,and the measurement array can be smaller than the source,thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then,an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement,as well as the identification and localization of noise sources.     

High-quality CdS quantum dots sensitized ZnO nanotube array films for superior photoelectrochemical performance

The surface characteristics of ZnO were synthetically optimized by a self-designed simultaneous etching and W-doping hydrothermal method utilizing as-prepared ZnO nanorod (NR) array films as the template. Benefiting from the etching and regrowth process and the different structural stabilities of the various faces of ZnO NRs, the uniquely etched and W-doped ZnO (EWZ) nanotube (NT) array films with larger surface area, more active sites and better energy band structure were used to improve the photoelectrochemical (PEC) performance and the loading quality of CdS quantum dots (QDs). On the basis of their better surface characteristics, the CdS QDs were uniformly loaded on EWZ NT array film with a good coverage ratio and interface connection; this effectively improved the light-harvesting ability, charge transportation and separation as well as charge injection efficiency during the PEC reaction. Therefore, all the CdS QD-sensitized EWZ NT array films exhibited significantly enhanced PEC performance. The CdS/EWZ-7 composite films exhibited the optimal photocurrent density with a value of 12 mA· cm^-2, 2.5 times higher than that of conventional CdS/ZnO-7 composite films under the same sensitization times with CdS QDs. The corresponding etching and optimizing mechanisms were also discussed.     

Optimization of the input surface of a thick-lens spatial-integrator array for maximum flux transfer efficiency

The radius of curvature of the input surface of a thick lens spatial integrator array is a free parameter that can be customized for a maximum flux transfer efficiency. With this procedure each element is different but the spatial integration feature remains for the whole array. The calculation is based on a real ray-tracing evaluation that also takes into account the transmissivity of the diopters. The flux transfer on the synthetic image is doubled when the input surfaces are propoerly optimized.     

Design and optimization of a nano-antenna hybrid structure for solar energy harvesting application

A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna(LSFNA) array for solar energy harvesting application. So, two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna(SEDNA). The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths of λres = 10 μm,15 μm, and 20 μm. Then the LSFNAs with three different sizes are modeled like a planar spiral-shaped array(PSSA).Also, a fractal bowtie nano-antenna is connected with the PSSA in the array gap. This proposed hybrid structure consists of two main elements:(I) Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal–insulator–metal diodes that are a proper method for infrared energy harvesting.(II) The PSSA gap is designed based on the electron field emission proposed by the Fowler–Nordheim theory for the array rectification. Finally,the proposed device is analyzed. The results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics(such as return loss, harvesting efficiency, etc.) than the previously proposed structures but also is a multi-resonance wide-band device. Furthermore, the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.     

Cymbal array: a broad band sound projector

A prototype 3 x 3 planar cymbal transducer array was built and tested. The array has a radiating area of 5.5 cm x 5.5 cm and a thickness of less than 8 mm. The measured transmitting voltage response was above 134 dB re 1 microPa/V @ 1 m and flat over the frequency range of 16 and 100 kHz. Array interaction was analyzed using an equivalent circuit model. The array interaction leads to variations in radiation resistance and velocity of the transducers in the array according to their surroundings in the array. The effect is enhanced overall efficiency and a flat response.     

Plasmon enhanced light trapping in thin film GaAs solar cells by Al nanoparticle array

Light trapping is a crucial factor to enhance the performance of thin film solar cells. For effective light trapping, we introduced Al nanoparticle array on the top and rear surface of thin film GaAs solar cells. The effect of both array on the optical absorption and current density of solar cells is investigated by using finite difference time domain (FDTD) method. The optimization process of top and rear array in solar cells is done systematically. The results indicate that by plasmonic action of arrays, the optical absorption is significantly enhanced and optimized structure yields a current density of 25.77 mA/cm². These enhancements are mainly attributed to surface plasmon effects induced by Al nanoparticles and the light grating properties of the arrays.     

The TRIUMF-ISAC gamma-ray escape suppressed specrometer, TIGRESS

The TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer is a high energy-resolution, high efficiency γ-ray detector array for radioactive beam experiments. It consists of high-purity germanium detectors with scintillator suppressors and waveform digitization. TIGRESS can operate in modes optimized for either maximum efficiency or for high peak-to-total, and can switch between these modes within a day. The digitized waveforms provide 6 mm FWHM position resolution for incident ¹³⁷Cs γ rays. The array hosts a suite of auxilliary detectors for charged particles and neutrons.     

AC space-charge effects in gyroklystron amplifiers

The effects of AC space charge on multicavity gyroklystron amplifiers are studied. It is found that when AC space charge is included in the analysis of weakly relativistic multicavity gyroklystron amplifiers, the optimized nonlinear efficiency becomes a function of beam current. For a cold beam (no velocity spread), the efficiency is maximum at zero current and decreases monotonically as the current increases. The zero current limit of the optimized efficiency when AC space-charge effects are included is not the same as the optimized efficiency with no space charge; it is significantly higher. This behavior is regularized when velocity spread is taken into account; in that case, the nonlinear efficiency increases with beam current until it reaches a maximum, then falls off slowly. The increase in efficiency is attributed to enhanced bunching associated with the saturation of the space-charge instability in the drift region; the reduction in efficiency at high current occurs because space charge induces an additional velocity spread in the beam     

高功率、高效率808nm半导体激光器阵列

通过设计高效率808 nm非对称宽波导外延结构,减少P型波导层和包层的自由载流子光吸收,实现腔内光吸收损耗为0.63 cm~(-1).制备的808 nm半导体激光器阵列在室温25?C下,实现驱动电流135 A,工作电压1.76 V,连续输出功率大于150 W,斜率效率高达1.25 W/A,中心波长809.3 nm,器件最高电光转换效率为65.5%,这是目前国内报道的808 nm半导体激光器阵列的最高电光转换效率,达到国际同类器件最好水平.     

Broadband absorption enhancement in randomly positioned silicon nanowire arrays for solar cell applications

In this Letter, the optical properties of randomly positioned silicon nanowire arrays are studied. The result shows that position randomization with a filling ratio larger than 36% renders better absorptance over a broadband ranging from 300 to 1130 nm compared to regular structures. The ultimate efficiency of a 48% filling ratio position randomized nanowire structure is 13.4% higher compared to the optimized regularly arranged nanowire structure with the same thickness. The absorptance enhancement of random structures is attributed to lowered reflectance, more supported resonant modes, and broadening of existing resonance.     

基于遗传算法的不等间距阵优化方法*

阵元数一定情况下,针对不等间距拖线阵高频信号处理存在的空间增益和无栅瓣兼容问题,提出一种基于遗传算法的不等间距拖线阵阵型优化方法。该方法以频带交互下最大旁瓣级最小作为约束因子,通过模拟生物自然进化过程搜索全局最优解,得到优化后的阵元位置。优化后阵型在保证低频信号处理空间增益不变情况下,实现对高频信号高空间增益、无栅瓣处理。计算机仿真结果表明：相比未优化阵型,在高频信号处理方面,优化后阵型在无栅瓣情况下,空间增益提升值近似理论值提升值;在低频信号处理方面,优化后阵型具有相同的空间增益。为实际不等间距拖线阵阵型优化和应用提供了一种思路。     

高功率双层径向线螺旋阵列天线实验研究

 介绍了高功率双层径向线螺旋阵列天线的模拟优化结果,对按照优化结构尺寸加工的阵列天线进行了实验研究。在实验中,设计了用于连接标准接口和天线输入口的阻抗变换器,对阵列天线辐射特性的测量采用了标准线极化天线比较法。实验结果表明：在3.8～4.2 GHz的频率范围内天线增益大于19.7 dB,口径效率大于42%,天线轴比小于4 dB,驻波系数小于1.6;实验结果与数值计算结果基本一致。     

Enhanced light extraction with silicon nanoantenna arrays for white light LED applications

High conversion efficiency and quantum efficiency is essential for the phosphor in an efficient phosphor-based white light LEDs. Here, based on the coherent harmonic and the random independent emitter model, we demonstrate theoretically that the silicon nanoantenna array can dramatically enhance the output power of emitters in a phosphor layer by investigating the far-field radiation enhancement of an electric dipole assisted by silicon nanopillars in a waveguide structure. Compared with the plasmonic silver nanoantenna array, the silicon nanoantenna array can increase the enhancement factor of light extraction efficiency (LEE) over 50% for the dipole source at the wavelength of 620 nm, thus showing potential applications in white light LEDs. The enhanced LEE is ascribed to the low-loss directional light scattering of silicon nanoantennas and the strong guided mode resonances caused by their array. The calculation results also indicate that the far-field radiation can be tailored significantly by changing the aspect ratio of silicon nanopillars while presenting a good directivity. Our research is expected to give more insights into the design and optimization of the solid-state lighting, gaining and lasing systems by integrating silicon-based nanoantennas.