Colloidal quantum dot for infrared-absorbing solar cells:State-oftheart and prospects

Colloidal quantum dot(CQD)shows great potential for application in infrared solar cells due to the simple synthesis techniques,tunable infrared absorption spectrum,and high stability and solution-processability.Thanks to significant efforts made on the surface chemistry of CQDs,device structure optimization,and device physics of CQD solar cells(CQDSCs),remarkable breakthroughs are achieved to boost the infrared photovoltaic performance and stability of CQDSCs.In particular,the CQDSC with a high power conversion efficiency of~14%and good stability is reported,which is very promising for infrared-absorbing solar cells.In this review,we highlight the unique optoelectronic properties of CQDs for the development of infrared-absorbing solar cells.Meanwhile,the latest advances in finely controlling surface properties of CQDs are comprehensively summarized and discussed.Moreover,the device operation of CQDSCs is discussed in-depth to highlight the impact of the device structure optimization of CQDSCs on their photovoltaic performance,and the emerging novel types of CQDSCs,such as semitransparent,flexible,and lightweight CQDSCs,are also demonstrated.The device stability of CQDSCs is also highlighted from the viewpoint of practical applications.Finally,the conclusions and possible challenges and opportunities are presented to promote the development steps of the CQDSCs with higher infrared photovoltaic performance and robust stability.

Nearly Perfect Absorbers Operating Associated with Fano Resonance in the Infrared Range

We fabricate a three-layer metamaterial of metal patterns/dielectric/metal films. The optical properties associated with Fano resonance of the metamaterials are investigated experimentally and theoretically. The results indicate that the introduction of Fano resonance due to symmetry breaking leads to a much wider absorption range. Furthermore, the amplitude and phase of reflection can be modulated effectively by adjusting various free parameters using the proposed structure.

A low-cost infrared absorbing structure for an uncooled infrared detector in a standard CMOS process

This paper introduces a low-cost infrared absorbing structure for an uncooled infrared detector in a standard 0.5 m CMOS technology and post-CMOS process. The infrared absorbing structure can be created by etching the surface sacrificial layer after the CMOS fabrication, without any additional lithography and deposition procedures. An uncooled infrared microbolometer is fabricated with the proposed infrared absorbing structure.The microbolometer has a size of 6565 m2and a fill factor of 37.8%. The thermal conductance of the microbolometer is calculated as 1.3310 5W/K from the measured response to different heating currents. The fabricated microbolometer is irradiated by an infrared laser, which is modulated by a mechanical chopper in a frequency range of 10–800 Hz. Measurements show that the thermal time constant is 0.995 ms and the thermal mass is 1.3210 8J/K. The responsivity of the microbolometer is about 3.03104V/W at 10 Hz and the calculated detectivity is 1.4108cm Hz1=2/W.

A Study on Nanoscale Infrared Absorbent Working in Waveband Range of 1300-400 cm^(-1)

Nanoscale powder of SiO2/Al2O3/TiO2 composite was prepared by sol-gel method. Microstructure and morphology of the obtained samples were characterized by infrared （IR）, X-ray diffraction （XRD） analysis and transmission electron microscopy （TEM）. It is proved that infrared absorbing peaks of the samples are in waveband range of 1300-400 cm^-1, and the peak shape changes with their component. Mechanism of the infrared peak＇s positions and shapes which changes with the size and morphology of the prepared nano-particles has been tentatively discussed.

Infrared emissivity and microwave absorbing property of epoxy-polyurethane/annealed carbonyl iron composites coatings

The microwave absorption property and infrared emissivity have been investigated for the single-layer coating made of the epoxy-polyurethane resin and carbonyl iron powders with variation of annealing treatment. Microwave-absorbing property was investigated by measuring the complex permittivity and complex permeability of the absorber in the frequency range from 2 to 18 GHz. Infrared emissivity value was measured using IR-2 Infrared Emissometer in the wavelength range of 8-14 μm. After annealing, the Fe （110） peak became sharp, and the crystallization improved significantly. Annealing treatment could reduce the sttrface energy of powders, improve compatibility between fillers and adhesives, and result in increase of the density of the coating. The lowest value of infrared emissivity （0.419） was obtained from the coating made of the carbonyl iron powder annealed at 700℃ for 1 h. With the variation of the annealing temperature, the magnetic and dielectric properties of the carbonyl iron particle were changed. The maximum reflection loss decreased and the matching frequency shifted to lower frequency with increasing the annealing temperature of carbonyl iron particles, which coincided with the variation of the complex permeability and permittivity according to the annealing temperature. Magnetic loss factor and dielectric loss factor of carbonyl iron particles were improved with increasing the annealing temperature in the 2-18 GHz range.

Visible-near infrared ultra-broadband polarization-independent metamaterial perfect absorber involving phase-change materials

We numerically demonstrate a novel ultra-broadband polarization-independent metamaterial perfect absorber in the visible and near-infrared region involving the phase-change material Ge_2Sb_2Te_5(GST).The novel perfect absorber scheme consists of an array of high-index strong-absorbance GST square resonators separated from a continuous Au substrate by a low-index lossless dielectric layer(silica)and a high-index GST planar cavity.Three absorption peaks with the maximal absorbance up to 99.94% are achieved,owing to the excitation of plasmon-like dipolar or quadrupole resonances from the high-index GST resonators and cavity resonances generated by the GST planar cavity.The intensities and positions of the absorption peaks show strong dependence on structural parameters.A heat transfer model is used to investigate the temporal variation of temperature within the GST region.The results show that the temperature of amorphous GST can reach up to 433 K of the phase transition temperature from room temperature in just 0.37 ns with a relatively low incident light intensity of 1.11×10~8W∕m^2,due to the enhanced ultra-broadband light absorbance through strong plasmon resonances and cavity resonance in the absorber.The study suggests a feasible means to lower the power requirements for photonic devices based on a thermal phase change via engineering ultra-broadband light absorbers.

Investigation of wide-angle thin metamaterial absorber at infrared region

In the practical application,a wide-angle absorption with simple structure is still crucial property of metamaterial absorbers(MAs).A single-band infrared MA is introduced to analyze the angle insensitive mechanism.Numerical simulation reveals that a perfect absorption peak with 99.9%(7.55μm)is achieved at normal incidence,as well as the absorptivity is respectively 69.7%(7.46μm)and 93.5%(7.46μm)for transverse electric(TE)and transverse magnetic(TM)modes at 70°incidence.By changing substrate thickness,the absorption ratio at 70°is increased to 91%(7.46μm)for TE mode.Our design can also keep the good absorption stability for the geometric parameters.The E z-field distributions for different incident angles are given to investigate the physical mechanism.The designed MA can realize good wide-angle tolerance.This MA owns great applications,including infrared spectroscopy,solar harvester and plasmonic sensors.

Optical transparent infrared high absorption metamaterial absorbers

In this work,an optical transparent infrared high absorption metamaterial absorber is proposed based on indium tin oxide(ITO)substrate.Due to the fact that ITO holds high reflectivity property in infrared region while transparent in optical region,ITO can be used in the application of Surface Plasmon Polaritons.In this design,three kinds of infrared metamaterial absorbers were proposed.All of them can achieve high absorption at 10.6μm while remaining transparent in visible region.LC equivalent circuit model was served as design foundation.The infrared absorption efficiency was numerically calculated and the mechanism analysis is given in the paper.The simulation results show that all three structures can achieve high absorption efficiency at 10.6μm under TE/TM polarization.The absorption remains high when the incident angle is less than 70°.Experimental results exhibit good accordance with simulation.

Near-Infrared Spectroscopy Combined with Absorbance Upper Optimization Partial Least Squares Applied to Rapid Analysis of Polysaccharide for Proprietary Chinese Medicine Oral Solution

Near-infrared (NIR) spectroscopy was applied to reagent-free quantitative analysis of polysaccharide of a brand product of proprietary Chinese medicine (PCM) oral solution samples. A novel method, called absorbance upper optimization partial least squares (AUO-PLS), was proposed and successfully applied to the wavelength selection. Based on varied partitioning of the calibration and prediction sample sets, the parameter optimization was performed to achieve stability. On the basis of the AUO-PLS method, the selected upper bound of appropriate absorbance was 1.53 and the corresponding wavebands combination was 400 - 1880 & 2088 - 2346 nm. With the use of random validation samples excluded from the modeling process, the root-mean-square error and correlation coefficient of prediction for polysaccharide were 27.09 mg·L-1 and 0.888, respectively. The results indicate that the NIR prediction values are close to those of the measured values. NIR spectroscopy combined with AUO-PLS method provided a promising tool for quantification of the polysaccharide for PCM oral solution and this technique is rapid and simple when compared with conventional methods.

Characteristics of radiation and convection heat transfer in indirect near-infrared-ray heating chamber

Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray （N/R） heating chamber. The effects of important design parameters such as the shape of heat absorbing cylinder and heat releasing fin on the pressure drop and heat transfer coefficient were analyzed with different Reynolds numbers. The Reynolds numbers were varied from 103 to 3x106, which was defined based on the hydraulic diameter of the heat absorbing cylinder. Analyses were performed to obtain the inner and outer flow and the temperature distributions in the heat absorbing cylinder and the rates of radiation heat transfer and convection heat transfer. As the Reynolds number increases, the convection heat transfer rate is increased while the radiation heat transfer rate is decreased. The average convection heat transfer rate follows a power rule of the Reynolds number. Addition of three-dimensional heat releasing fin to the outside of the heat absorbing cylinder enhances the convection heat transfer.

A thin radar-infrared stealth-compatible structure:Design,fabrication,and characterization

A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.

Recent Progresses on Passively Switched Mid-Infrared Fiber Lasers at 3 μm

We present the recent research progress of our group on mid-infrared pulsed fiber lasers at 3μm by passive switching. Three different kinds of saturable absorbers including semiconductor saturable absorber （SESAM）, Fe2＋：ZnSe crystal, topological insulator （TI） were used to perform the pulse generation, respectively. The temporal regimes of mode locking, Q-switching and Q-switching induced gain switching were gained. Some relative discussions and prospective efforts are proposed at the end of this paper.

基于电介质超材料的中红外超窄带吸波器

电介质超材料因具有极低欧姆损耗受到广泛关注.提出一种基于电介质超材料的中红外超窄带吸波器,该吸波器由顶层电介质微结构、中间层电介质膜和基底金属构成.研究结果表明:该吸波器在中红外波段存在带宽为2.40nm的吸收峰;电场主要分布于顶层硅微结构之间的间隙,导致吸收损耗功率显著降低,进而实现吸收带宽压缩;作为传感器时,在中红外波段该吸波器的品质因数可达80.可见,该吸波器可应用于中红外热辐射光源和高性能传感器.

微波吸波材料在太赫兹、红外段反射谱测量研究

吸波材料是外形隐身技术的有效补充技术,电磁波进入到吸波材料内部后,应该被迅速地最大限度的衰减掉,因此,在设计吸波材料的电磁参数时,一方面要考虑阻抗匹配,使电磁波最大限度地进入到材料内部,另一方面,要确保进入到材料内部的电磁波尽可能被全部衰减掉。对吸波材料来说,也就是材料要有较大的介电常数虚部和磁导率的虚部,它们会引起电磁波能量的衰减。传统的吸波材料主要针对于微波,随着技术的发展,太赫兹雷达已投入使用,传统的微波吸波材料能否对太赫兹频段、乃至红外段有效衰减,以及这些吸波材料在太赫兹频段的评估成为了有必要研究和探讨的问题。分别基于矢量网络分析仪的微波暗室测量系统、太赫兹时域光谱测量系统、以及傅里叶变换光谱系统对2种微波段吸波材料板开展深入测量研究,在微波段反射率测量基础上,拓展到太赫兹、红外波段,测量了这些材料1 GHz~180 THz的雷达吸波材料反射率。测量结果表明,随着频率的升高,吸波材料表面形态、粗糙度对反射率形成了一定的影响,并针对这种影响在太赫兹、红外波段进一步开展了吸波材料反射特性随角度的变化的研究;为了弄清吸波材料在太赫兹、红外频段的吸波原理,将吸波涂层从金属衬板上剥离后进行了测量,获得了该吸波涂层2~180 THz的反射率、透射率,并基于Kamers-Kronig关系计算了该复合吸波材料等效的介电参数,测试结果证明,微波波段的吸波材料在太赫兹、远红外频段仍具备一定的吸波能力,太赫兹、红外不足以穿透该吸波材料的反射涂层到达金属衬板,其吸收主要来自反射吸收和吸波材料表面的散射。

基于超材料吸波结构的MEMS热电堆红外温度传感器设计

提出了一种基于超材料吸波结构的MEMS热电堆红外温度传感器,避免了使用特殊的滤光片进行封装,从而降低了传感器的体积。在设计上,采用超材料吸波结构将待测目标辐射的红外光选择性吸收,并将光能转化为热。通过利用时域有限差分方法研究了超材料吸波结构的结构参数与红外吸收光谱和吸收率之间的关系,并优化出用于检测人体红外辐射的超材料吸波结构尺寸。结果表明,当红外光波长范围为9.5μm~10.5μm时,该传感器的红外吸收率优于0.38,其中在波长为9.989μm处出现红外吸收峰,其最大吸收值为0.997。由超材料吸波结构产生的热量传递到其下方的热电堆,通过多物理场仿真可得热电堆的热端和冷端的温差为0.046 K,进而转化为输出电压,从而验证了整体设计的有效性。

基于超材料的宽带红外吸波器

为了解决红外领域对高性能吸波器的需求问题,设计了一种基于超材料的宽带红外吸波器。此吸波器在“金属-介质-金属”三层结构基础上,通过设计印刷在介质基板上层的金属图案,实现了红外(10.0~12.7 THz)频段范围的宽带吸收,吸收率在90%以上的相对带宽达到了23%。分析了吸波器不同尺寸参数对吸收率的影响,并通过S参数反演法得到了吸波器的等效介电常数和等效磁导率,同时采用等效媒质理论、干涉相消理论分析了吸波器的吸波机理。此外,设计的吸波器还具备极化不敏感、高吸收率、剖面低的优点,并在一定入射角范围内保持稳定的工作带宽。

电磁超表面在隐身技术中的应用研究进展

电磁超表面能够利用散射调控和电磁波吸收2种主要机理进行隐身是隐身技术中一种极具潜力的新型技术途径。对电磁超表面在隐身技术中的应用与研究进展进行综述,首先介绍了超表面散射调控机理进行隐身设计的基本原理与实现方法,介绍了相位梯度超表面、编码超表面和超表面隐身套的发展历程和研究成果;其次介绍了基于吸波机理的超表面隐身技术研究进展,包括完美吸波结构、多频带吸波结构、宽频带吸波结构、宽角域吸波结构;再次介绍了超表面雷达隐身与其他功能的复合设计研究,包括超表面隐身强度复合设计、超表面吸波透波散射一体化、雷达红外兼容隐身等内容;最后总结了一些超表面在隐身技术应用中存在的问题和未来的研究方向。

红外光谱气体录井随钻评价技术

近年来随着非常规油气藏的开发,油气勘探复杂程度显著上升,地下流体关系愈发复杂,增大了快速、准确评价地层流体,发现薄层、裂缝型、弱显示油气层的难度,为勘探开发提供决策依据的需求更加紧迫。针对复杂储层薄互层识别困难、非常规油气流体性质判识困难等难点,开展了基于气体分子光谱原理的红外光谱录井特色技术研究。该项技术分析周期≤8 s,在快速钻井条件下不易漏失油气层,特别是在油气水层随钻流体评价、裂缝型/薄层油气藏识别及储层精细划分与界线卡取方面更具技术优势。基于红外光谱气体录井技术,建立了储层能级谱图评价模型和储层流体性质评价标准,并在井场实际应用中取得较好效果,有效解决了在快速钻井条件下储层流体识别评价的难题。

近红外光谱技术在快速检测辣椒粉吸光度中的应用研究

为提高辣椒粉吸光度的检测效率,以新疆辣椒粉为建模材料,使用波通、蔡司和赛默飞3个品牌的近红外光谱仪对辣椒粉进行扫描建模,确定最佳方式为赛默飞近红外光谱仪在波数精度16 cm^(-1)条件下采集光谱,利用偏最小二乘法建立模型。经过一阶导数+SG平滑两步光谱预处理方式,并选择主因子数为15,对模型进行优化。校正均方根误差(Root Mean Square Error of Calibration,RMSEC)为0.218,校正相关系数(Correlation Coefficient of Calibration,Rc)为0.9934;日内精密度(n=3)最大为1.22%,日间精密度(n=3)最大为0.98%,93%的样品化学实验值与近红外模型预测值两者之差在0.6以内,结果表明该近红外模型稳定性好,精确度高,能实现辣椒粉吸光度的快速检测。