Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx,values typically found in indoor environments.Flexible cells were developed using either low-temperature sol-gel or atomiclayer-deposited compact layers over conducting polyethylene terephthalate (PET)substrates,together with ultraviolet (UV)-irradiated nanoparticle TiO2 scaffolds,a CH3NH3PbI3-xClx perovskite semiconductor,and a spiro-MeOTAD hole transport layer.By guaranteeing high-quality carrier blocking (via the 10-40 nm-thick compact layer) and injection (via the nanocrystalline scaffold and perovskite layers) behavior,maximum power conversion efficiencies (PCE) and power densities of 10.8％ and 7.2 μW.cm-2,respectively,at 200 lx,and 12.1％ and 16.0 μW·cm-2,respectively,at 400 lx were achieved.These values are the state-of-the-art,comparable to and even exceeding those of flexible dye-sensitized solar cells under LED lighting,and significantly greater than those for flexible amorphous silicon,which are currently the main flexible photovoltaic technologies commercially considered for indoor applications.Furthermore,there are significant margins of improvement for reaching the best levels of efficiency for rigid glass-based counterparts,which we found was a high of PCE ～24％ at 400 lx.With respect to rigid devices,flexibility brings the advantages of being low cost,lightweight,very thin,and conformal,which is especially important for seamless integration in indoor environments.     

Enhanced light trapping in dye-sensitized solar cell by coupling to 1D photonic crystal and accounting for finite coherence length

Theoretical analysis of dye-sensitized solar cell integrated with photonic crystals based on coupled coherent and geometrical optics formalism has presented. The effect of structural parameters, such as thickness of layer, number of unit cells and light incident angle on the optical properties and photo-current magnification for the proposed photonic crystal based dye-sensitized solar cell have studied. The angular response of the cell in terms of light harvesting efficiency and cumulative photo-generation rate has also analysed. A strategy has presented to enhance the performance of the cell under oblique incidence. The effect of number of photonic crystal unit cells has also analysed in view of percentage enhancement in cumulative photo-generation rate. This work provides new insight into the design and tailoring of the photonic crystals to enhance the light harvesting efficiency in the solar cells.     

Energy harvesting for self-powered nanosystems

In this article, an introduction is presented about the energy harvesting technologies that have potential for powering nanosystems. Our discussion mainly focuses on the approaches other than the well-known solar cell and thermoelectrics. We mainly introduce the piezoelectric nanogenerators developed using aligned ZnO nanowire arrays. This is a potential technology for converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as fl ow of body fl uid, blood fl ow, contraction of blood vessel, dynamic fl uid in nature) into electric energy for self-powered nanosystems.     

新型相干结构光场调控及应用研究进展

结构光场的空域调控包括振幅、相位、偏振、相干度等丰富自由度,对其自由度的单一或联合调控引发了一系列新奇物理效应,在新型结构光场构建及多种领域中具有重要应用。相比于完全相干光场,部分相干光场在抵抗散斑噪声和大气湍流扰动等方面具有独特优势。近年来,具有新型相干结构的部分相干光束在大气传输、光学加密与成像、信息鲁棒传输、高质量光束整形等领域有着重要研究价值。本文详细综述了具有新型相干结构部分相干光场的理论构建与实验合成的研究进展,并重点介绍了新型相干结构光场在复杂环境中的鲁棒传输特性及其在光学加密、成像、鲁棒信息传输及光束整形中的应用研究进展。研究表明,新型相干结构光场调控不仅提供了一种有效抵抗复杂环境扰动的有效手段,而且丰富了光场调控技术在多种领域中的应用。最后,对新型相干结构调控技术发展趋势及潜在应用前景进行了展望。

     

Unpolarized light beams with different coherence properties

We investigate the coherence properties of unpolarized beams. Such beams form a much richer class than has been previously realized. We illustrate our results by examples.     

Fluorescence Anisotropy Reloaded—Emerging Polarization Microscopy Methods for Assessing Chromophores' Organization and Excitation Energy Transfer in Single Molecules,Particles, Films,and Beyond

Fluorescence polarization is widely used to assess the orientation/rotation of molecules, and the excitation energy transfer between closely located chromophores. Emerging since the 1990s, single molecule fluorescence spectroscopy and imaging stimulate the application of light polarization for studying molecular organization and energy transfer beyond ensemble averaging. Here, traditional fluorescence polarization and linear dichroism methods used for bulk samples are compared with techniques specially developed for, or inspired by, single molecule fluorescence spectroscopy. Techniques for assessing energy transfer in anisotropic samples, where the traditional fluorescence anisotropy framework is not readily applicable, are discussed in depth. It is shown that the concept of a polarization portrait and the single funnel approximation can lay the foundation for alternative energy transfer metrics. Examples ranging from fundamental studies of photoactive materials (conjugated polymers, light‐harvesting aggregates, and perovskite semiconductors) to Förster resonant energy transfer (FRET)‐based biomedical imaging are presented. Furthermore, novel uses of light polarization for super‐resolution optical imaging are mentioned as well as strategies for avoiding artifacts in polarization microscopy.     

基于并联电感同步开关控制的振动能量回收方法研究

针对振动能量回收使用的并联电感同步开关(SSHI)控制方法研究中未考虑的控制损耗、储能负载和激励环境等问题,设计了一种基于电流监控、比较器、单片机和双向电子开关的低功耗回收控制电路。单片机通过比较器产生的中断信号控制双向开关适时闭合,成功实现了并联SSHI回收控制电路的功能。以储能装置为负载时,分析了整流电压、振子电容、激励幅值和频率对并联SSHI回收电路控制效果的影响,结果表明该方法在整流电压值较高、振子电容较大、激励频率较高、激励力较小时能够更有效地提高回收效率,为并联SSHI控制方法的应用奠定了一定的理论基础。     

基于电磁感应能量捕获技术的磁流变阻尼器研究

针对目前智能结构磁流变阻尼器工作时需要外部电能输入的问题,提出一种可以自行获得电能、无需外部电能输入的新型磁流变阻尼器。与常规的磁流变阻尼器相比,该新型磁流变阻尼器能利用自带的电磁感应能量捕获结构将外界环境振动能量转换为其自身可用的电能,从而省去外部电源设备,提高磁流变振动控制系统的可靠性。首先论述该新型磁流变阻尼器的结构特征及其电能收集的理论模型,然后对其捕获电能的能力进行模拟仿真,最后在实验台架上对实际加工的实验器件原型进行实验研究。实验结果表明:在外界振动条件下,该新型磁流变阻尼器可以在无需外界电能输入的情况下改变阻尼特性,实现对振动的无源智能控制。     

基于同步电感及buck-boost转换器的能量回收接口技术

设计基于同步电感及buck-boost转换器的接口技术—SCEI(Synchronous Charge Extraction and Inversion),完成该接口技术在恒定激振位移、恒定激振力情况下回收功率的理论分析及计算。理论计算表明,在恒定激振位移下忽略buck-boost转换效率时SCEI的回收功率大于Parallel-SSHI技术最大回收功率,且该回收功率与负载无关;在恒定激振力下SCEI回收功率与SECE技术特性相似;通过实验比较设计的SCEI技术与4种经典技术在相同激振位移下的回收功率。实验结果表明,SCEI技术回收功率约为SECE的1.5倍,且与负载无关。     

Pushing thermoelectric generators toward energy harvesting from the human body: Challenges and strategies

Advances in miniaturized portable electronics and progress on novel enabling technologies, consequently accompanied by power consumption downgraded from the scale of milliwatts (mW) to microwatts (μW), have inevitably facilitate the development of an emerging discipline-wearable human energy conversion systems. Served as a passive human energy harvester which can directly convert heat into electricity in long-term operations without the user’s intervention, wearable thermoelectric generators (WTEG) have sparked considerable research interest for next-generation power supply. In comparison to the longstanding research history of thermoelectrics, their wearables are still in infancy of extensive growth over the last decade. Although, historically, the main challenge behind the conventional thermoelectric generator (TEG) is the improvement of dimensionless figure-of-merit (zT), wearable applications usually impose additional restrictions that can be more pivotal than zT value. Diversified targeted strategies therefore have been proposed to push TEG toward wearable application. Here, we review the evolutionary roadmap of the wearable thermoelectric generators in the past decade, it could be concluded that the trend in WTEG is to move toward stretchable three-dimension (3D)-structure with rational thermal design at the moment. The basic concept targeting WTEG, which highly differs from that of the traditional TEG, is introduced at first. And then, aiming to provide detailed design guidelines for WTEG, we begin with carefully discussing the key issues for TEG toward wearable application. Finally, the specific strategies targeted WTEG that is classified into thermal design regarding extrinsic temperature difference (ΔT_ext), parasitic and TEG thermal resistance, mechanical design with emphasis on optimizing deformability at materials/device level beyond flexibility toward stretchability, as well as architecture design from two-dimension (2D) to 3D feature are comprehensively summarized, respectively. With these understandings, perspectives for the future development of WTEG are outlined. This review emphasizes issues and provides additional insight in advanced strategies for pushing TEG toward wearable application. The key issues clarified and the design roadmap summarized here arise from the goal of providing ideas for the concurrent optimization of the future WTEG, as well as realistically promoting the TEG toward wearable application.     

基于谐振器的多模态压电换能结构研究

传统压电悬臂梁俘能器一般通过其基频与环境中某一激振频率的匹配来收集这个频率上的振动能,为俘获环境中多个激振频率上的能量,提出一种在压电悬臂梁上附加谐振器的多模态换能结构,由该结构组成的俘能器的前两阶共振频率可以被设计在给定的激振频率上,从而有效地收集分布在这两个频率上的能量.实验表明附加谐振器有效地提高了俘能效率,其中一阶模态的俘能效率相对附加等量质量块时提高了71％,二阶模态的俘能效率与原压电悬臂梁的一阶模态相当.     

Advanced triboelectric materials for liquid energy harvesting and emerging application

Triboelectric properties of materials play an essential role in liquid energy harvesting and emerging application. The triboelectric properties of materials can be controlled by chemical functionalization strategy, which can improve the utilization of liquid energy resources or reduce the hazards of electrostatic effects. Herein, the latest research progress in molecular modification based on chemical functionalization to control triboelectric properties of materials is systematically summarized. By introducing the mechanism of contact electrification between liquid and solid materials and the developmental history of liquid–solid contact electrification, the influence of solid surface charge density, wettability and liquid properties on contact electrification of liquid and solid materials is described. Research progress on chemical functionalization for improving the hydrophobicity of solid materials, surface charge density of solid materials and triboelectric properties of liquid materials is highlighted. The focus then turns to the significance of enhanced liquid–solid contact electrification in energy harvesting, self-powered sensors and metal corrosion protection. Recent advances in chemical functionalization strategies for weakening the triboelectric properties of solid and liquid materials are also highlighted. Finally, an outlook of the potential challenges for developing chemical functionalization strategies in the field of solid surface modification and liquid molecular modification is presented.     

Triboelectric energy harvesting with surface-charge-fixed polymer based on ionic liquid

A novel triboelectric energy harvester has been developed using an ionic liquid polymer with cations fixed at the surface. In this report, the fabrication of the device and the characterization of its energy harvesting performance are detailed. An electrical double layer was induced in the ionic liquid polymer precursor to attract the cations to the surface where they are immobilized using a UV-based crosslinking reaction. The finalized polymer is capable of generating an electrical current when contacted by a metal electrode. Using this property, energy harvesting experiments were conducted by cyclically contacting a gold-surface electrode with the charge fixed surface of the polymer. Control experiments verified the effect of immobilizing the cations at the surface. By synthesizing a polymer with the optimal composition ratio of ionic liquid to macromonomer, an output of 77 nW/cm² was obtained with a load resistance of 1 MΩ at 1 Hz. This tuneable power supply with a μA level current output may contribute to Internet of Things networks requiring numerous sensor nodes at remote places in the environment.     

Cold white light generation through the simultaneous emission from Ce3+ and Tb3+ in sodium germanate glass

A spectroscopic investigation of sodium germanate glasses activated with Ce³⁺, Tb³⁺ and Ce³⁺/Tb³⁺ is carried out by analyzing their photoluminescence spectra and decay times. Non-radiative energy transfer from Ce³⁺ to Tb³⁺ is observed upon near-UV excitation at 310 nm (peak emission wavelength of AlGaN-based LEDs). The non-radiative nature of this energy transfer is inferred from the increase in the decay rate of the Ce³⁺ emission when the glass is co-doped with Tb³⁺. From an analysis of the Ce³⁺ emission decay time curve it is inferred that an electric dipole–quadrupole interaction might to be the dominant mechanism for the Tb³⁺ emission sensitized by Ce³⁺. Energy transfer from Ce³⁺ to Tb³⁺ leads to a simultaneous emission of these ions in the blue, green, yellow and red, resulting in white light with CIE1931 chromaticity coordinates, x = 0.30 and y = 0.32, which correspond to cold white light with a colour temperature of 7320 K and very small deviation from the Planckian black-body radiator locus (0.005).     

Z型梁结构压电式能量采集性能分析

振动能量采集能够将外部环境中的振动能转化为电能,具有绿色可持续、节能环保、设计灵活等优势,在工业、生物、医学、军事等领域具有广阔的应用前景.为使振动型能量采集器适应更为复杂多变的工作环境,提高其采集功率和工作频带,提出一种多梁结构-Z型梁结构压电式能量采集器.理论分析了该采集器的固有振动特性,并通过有限元分析了结构尺寸...