纳米材料和技术在可再生能源方面的应用

纳米光子学,产生于纳米技术和光子学的交界处,处理光和物质在纳米尺度的相互作用,可以被用来产生新的效果和发展纳米尺度的器件。世界在迎接未来能源需求方面正面临巨大挑战。纳米光子学为太阳能转换提供了新的进展。在太阳能转换领域,我们正加速开展新的基于纳米光子学让太阳光子在整个光谱范围从紫外到红外有效率地被吸收和转换,并且有效率地转换为电能方面的研究（比如直接或者电化学的转换）。纳米技术也为热电和能量储存方面的研究提供了新的途径,我们正追求把它们和太阳能获取整合在一起从而提供广泛的能源解决方案。     

Photovoltaic devices

The term photovoltaics refers to the process whereby the energy in light is directly converted into useful electrical energy. Sunlight is abundant and free; hence, the conversion of this effectively inexhaustable energy source into electrical energy by photovoltaics is of considerable interest. Photovoltaic devices for solar energy conversion (solar cells) are the subject of this article.     

Extending absorption of near-infrared wavelength range for high efficiency CIGS solar cell via adjusting energy band

The efficient photon harvesting in near infrared wavelength range is still a challenging problem for high performance Cu(In_1-x, Ga_x)Se₂ (CIGS) solar cell. Herein, adjusting the energy band distribution of CIGS solar cell could provide significant academic guidance for devices with superior output electric power. To understand the role of each functional layer, the optimal 3000 nm CIGS absorber layer with 1.3 eV bandgap and 30 nm CdS buffer layer were firstly obtained via simulating the uniform band-gap structures. By introducing CIGS absorber layer with a double grading Ga/(Ga+In) profile, the power conversion efficiency of the double gradient band gap cell is superior to that of uniform band-gap cell through extending absorption of near-infrared wavelength range. Upon optimization, the best power conversion efficiency of CIGS with a double gradient band gap solar cell is improved significantly to 24.90%, among the best values reported in literatures, which is an 8.17% relative increase compared with that of the uniform band-gap cell. Our findings provide a theoretical guide toward the design of high performance solar cells and enrich the understandings of the energy band engineering for developing of novel semiconductor devices.     

Excitation energy transfer in covalently bonded porphyrin heterodimers

We describe the photophysical properties of heterodimers that are formed by the free base 2-(2-carboxyvinyl)-5,10,15,20-tetraphenylporphyrin and the zinc complex of 5-(p-aminophenyl)-10,15,20-triphenylporphyrin and that are covalently bonded by the amide link. These dimers differ in the configuration of the double bond in the spacer group. We determine fluorescence quantum yields of heterodimers and their porphyrin components. The energy transfer rate constants have been estimated from the measured fluorescence lifetimes and fluorescence excitation spectra and, also, they have been calculated from the steady-state absorption and fluorescence spectra according to the Förster theory. We have found that the efficiency of the intramolecular energy transfer in heterodimers is 0.97–0.99, and the energy migration rate constants have been found to be (1.82–4.49) × 10¹⁰ s^?1. The results of our investigation show that synthesized heterodimers can be used as efficient light-harvesting elements in solar energy conversion devices.     

Design of AlInN on silicon heterojunctions grown by sputtering for solar devices

AlInN alloys offer great potential for photovoltaics thanks to their wide direct bandgap covering the solar spectrum from the infrared (0.7 eV – InN) to the ultraviolet (6.2 eV – AlN), and their superior resistance to high temperatures and high-energy particles. We report the design of AlInN-on-silicon heterojunctions grown by radio-frequency sputtering to explore their potential for low-cost devices. Particularly, we study the influence of AlInN bandgap energy, thickness and carrier concentration, silicon surface recombination, interface defect density and wafer quality, on the photovoltaic properties of the junction. The effect of introducing an anti-reflective coating is also assessed. Optimized AlInN-on-Si structures show a conversion efficiency of 23.6% under 1-sun AM1.5G illumination. In comparison with silicon homojunctions, they own an improved responsivity at wavelengths below 500 nm. These results make AlInN-on-Si heterojunctions a promising technology for solar devices with impact in space applications. Experimental results on novel AlInN-on-Si solar cells are also presented.     

晶格小失配InGaAsP材料特性及太阳电池应用

Ⅲ-Ⅴ族太阳电池效率的持续提升要求对能量转换材料的带隙宽度进行更细致划分,以实现对全光谱的高效利用。在短波红外波段,四元InGaAsP混晶材料因在带隙宽度和晶格常数的调节上具有很好的可操作性,是一种极具潜力的短波红外光电转换材料。本文对InGaAsP材料生长及子电池器件制备进行了研究,通过时间分辨荧光光谱、高分辨X射线衍射等表征手段对室温下晶格失配的InGaAsP材料进行了测试分析。实验结果表明,在一定程度负失配生长条件下,InGaAsP材料质量随着负失配程度逐渐提高。在后续电池制备过程中,一定程度负失配同样有助于电池器件性能提升,制备的单结电池开路电压由晶格匹配时的633 mV提高到负失配条件下的684 mV,从而为高效多结太阳电池的应用提供了新的技术路线。     

有机太阳能电池研究进展

为了减轻当前能源危机所带来的压力,各国在太阳能电池等清洁能源领域投入了大量的人力、物力和财力.由于有机太阳能电池具有独特的优点(有机材料易于修饰,器件制备方法简便且可制备出柔韧器件),并且随着相关研究的深入,有机太阳能电池的能量转换效率逐步得到提高,这昭示了有机太阳能电池商业化的美好前景,目前已经有大批科研工作者投身于有机太阳能电池领域的研发工作.文章从太阳能电池小分子材料、聚合物材料和提高有机太阳能电池能量转换效率的方法这三方面入手,对有机太阳能电池领域进行综述.     

First-principle study of the structural,electronic,and optical properties of SiC nanowires

We preform first-principle calculations for the geometric, electronic structures and optical properties of SiC nanowires(NWs). The dielectric functions dominated by electronic interband transitions are investigated in terms of the calculated optical response functions. The calculated results reveal that the SiC NW is an indirect band-gap semiconductor material except at a minimum SiC NW(n = 12) diameter, showing that the NW(n = 12) is metallic. Charge density indicates that the Si–C bond of SiC NW has mixed ionic and covalent characteristics: the covalent character is stronger than the ionic character, and shows strong s–p hybrid orbit characteristics. Moreover, the band gap increases as the SiC NW diameter increases. This shows a significant quantum size and surface effect. The optical properties indicate that the obvious dielectric absorption peaks shift towards the high energy, and that there is a blue shift phenomenon in the ultraviolet region. These results show that SiC NW is a promising optoelectronic material for the potential applications in ultraviolet photoelectron devices.     

太阳能光伏/光热化学利用系统

本文研究了一种基于光谱分频的太阳能光伏/光热化学耦合利用系统。在该系统中,全光谱的太阳能按照波长不同被区分利用。适合光伏电池利用的太阳能被分配给光伏电池进行光伏转换,其它波段的太阳能则转化为热能驱动甲醇裂解反应产生合成气。实验结果表明在太阳辐照强度为712.8 W/㎡,甲醇流量为2.7 kg/h时,系统效率达到31.18%。系统实现了低品位的太阳能向高品位的电能和化学能的转换,为研究太阳能的全光谱高效利用提供了新的思路。     

Oxide semiconductors for solar to chemical energy conversion: nanotechnology approach

The present work considers the application of oxide semiconductors in the conversion of solar energy into the chemical energy required for water purification (removal of microbial cells and toxic organic compounds from water) and the generation of solar hydrogen fuel by photoelectrochemical water splitting. The first part of this work considers the concept of solar energy conversion by oxide semiconductors and the key performance-related properties, including electronic structure, charge transport, flat band potential and surface properties, which are responsible to the reactivity and photoreactivity of oxides with water. The performance of oxide systems for solar energy conversion is briefly considered in terms of an electronic factor. The progress of research in the formation of systems with high performance is considered in terms of specific aspects of nanotechnology, leading to the formation of systems with high performance. The nanotechnology approach in the development of high-performance photocatalysts is considered in terms of the effect of surface energy associated with the formation of nanostructured system on the formation of surface structures that exhibit outstanding properties. The unresolved problems that should be tackled in better understanding of the effect of nanostructures on properties and performance of oxide semiconductors in solar energy conversion are discussed. This part is summarised by a list of unresolved problems of crucial importance in the formation of systems with enhanced performance. This work also formulates the questions that must be addressed in order to overcome the hurdles in the formation of oxide semiconductors with high performance in water purification and the generation of solar fuel. The research strategy in the development of oxide systems with high performance, including photocatalysts for solar water purification and photoelectrodes for photoelectrochemical water splitting, is considered. The considerations are focused on the systems based on titanium dioxide of different defect disorder as well as its solid solutions and composites.     

室内光伏的应用前景与挑战

社会的发展离不开能源的发现与创造,光伏能源的多形式运用在能源领域大放异彩,室 内光伏器件逐渐成为大家所关注的热点。室内光伏IPV (Indoor photovoltaics) 作为低照度条件 下的电源,可以满足低功率电子器件的工作要求。本文主要比较了基于硅、染料、III-V 族半导 体、有机化合物和卤化物钙钛矿这些不同类型的IPV 器件。得益于卤化物钙钛矿活性层具有优 异的光物理特性,钙钛矿光伏具有成为高性能室内光伏器件的潜力。与此同时也讨论了室内光伏 的局限性。最后,提出了制备生产高效率、无毒、稳定的钙钛矿室内光伏器件的解决方案以及未 来应用展望。     

An overview of engineered porous material for energy applications: a mini-review

The ordered porous materials, developed using various templating materials, have generated huge interest among the electrochemist community due to their plenty of unique properties and functionalities that can be effectively applied in optoelectronic devices. Mesoporous materials possess excellent opportunities in energy storage and energy conversion applications due to their extraordinarily high surface area and large pore size. These properties may enhance the performance of porous materials in terms of lifetime and stability, energy and power density. In this review, we have tried to club the fields of optoelectronics and mesoporous materials. Also, we have summarised the primary methods for preparing mesoporous materials using various templates and described their applications as electrodes and catalysts in fuel cells, solar fuel production, dye-sensitised solar cells, perovskite, supercapacitors and rechargeable batteries. Finally, we have highlighted the research and development challenges of mesoporous materials those need to be overcome to enhance their contribution in renewable energy applications.     

Dye-sensitized solar cells based on ZnO nanowire array/TiO2 nanoparticle composite photoelectrodes with controllable nanowire aspect ratio

The ZnO nanowire (NW) array/TiO₂ nanoparticle (NP) composite photoelectrode with controllable NW aspect ratio has been grown from aqueous solutions for the fabrication of dye-sensitized solar cells (DSSCs), which combines the advantages of the rapid electron transport in ZnO NW array and the high surface area of TiO₂ NPs. The results indicate that the composite photoelectrode achieves higher overall photoelectrical conversion efficiency (η) than the ZnO NW alone. As a result, DSSCs based on the ZnO NW array/TiO₂ NP composite photoelectrodes get the enhanced photoelectrical conversion efficiency, and the highest η is also achieved by rational tuning the aspect ratio of ZnO NWs. With the proper aspect ratio (ca. 6) of ZnO NW, the ZnO NW array/TiO₂ NP composite DSSC exhibits the highest conversion efficiency (5.5 %). It is elucidated by the dye adsorption amount and interfacial electron transport of DSSCs with the ZnO NW array/TiO₂ NP composite photoelectrode, which is quantitatively characterized using the UV-Vis absorption spectra and electrochemical impedance spectra. It is evident that the DSSC with the proper aspect ratio of ZnO NW displays the high dye adsorption amount and fastest interfacial electron transfer.     

银纳米线表面等离激元波导的能量损耗

金属纳米结构的表面等离激元可以突破光学衍射极限,为光子器件的微型化和集成光学芯片的实现奠定基础.基于表面等离激元的各种基本光学元件已经研制出来.然而,由于金属结构的固有欧姆损耗以及向衬底的辐射损耗等,表面等离激元的传输能量损耗较大,极大地制约了其在纳米光子器件和回路中的应用.研究能量损耗的影响因素以及如何有效降低能量损耗对未来光子器件的实际应用具有重要意义.本文从纳米线表面等离激元的基本模式出发,介绍了它在不同条件下的场分布和传输特性,在此基础上着重讨论纳米线表面等离激元传输损耗的影响因素和测量方法以及目前常用的降低传输损耗的思路.最后给出总结以及如何进一步降低能量损耗方法的展望.表面等离激元能量损耗的相关研究对于纳米光子器件的设计和集成光子回路的构建有着重要作用.     

Electrical, structural and surface properties of fluorine doped tin oxide films

Fluorine (F) incorporated polycrystalline SnO₂ films have been deposited onto glass substrates by ultrasonic spray pyrolysis technique. To possess information about the electrical properties of all films, their electrical conductivities were investigated depending on the temperature, and their activation and trap energies were analyzed. The crystalline structure, surface properties and elemental analysis of the SnO₂ films were examined to determine the effect of the F element. After all investigations, it was concluded that each fluorine incorporation rate has a different and important effect on the physical properties, and SnO₂:F (3 at%) films were found to be the most promising sample for energy conversion devices, especially as conducting electrode in solar cells with its improved structural and electrical properties as compared to others.     

Synthesis of hybrid organic–inorganic nanocomposite materials based on CdS nanocrystals for energy conversion applications

Efficient solar energy conversion is strongly related to the development of new materials with enhanced functional properties. In this context, a wide variety of inorganic, organic, or hybrid nanostructured materials have been investigated. In particular, in hybrid organic–inorganic nanocomposites are combined the convenient properties of organic polymers, such as easy manipulation and mechanical flexibility, and the unique size-dependent properties of nanocrystals (NCs). However, applications of hybrid nanocomposites in photovoltaic devices require a homogeneous and highly dense dispersion of NCs in polymer in order to guarantee not only an efficient charge separation, but also an efficient transport of the carriers to the electrodes without recombination. In previous works, we demonstrated that cadmium thiolate complexes are suitable precursors for the in situ synthesis of nanocrystalline CdS. Here, we show that the soluble [Cd(SBz)₂]₂·(1-methyl imidazole) complex can be efficiently annealed in a conjugated polymer obtaining a nanocomposite with a regular and compact network of NCs. The proposed synthetic strategies require annealing temperatures well below 200 °C and short time for the thermal treatment, i.e., less than 30 min. We also show that the same complex can be used to synthesize CdS NCs in mesoporous TiO₂. The adsorption of cadmium thiolate molecule in TiO₂ matrix can be obtained by using chemical bath deposition technique and subsequent thermal annealing. The use of NCs, quantum dots, as sensitizers of TiO₂ matrices represents a very promising alternative to common dye-sensitized solar cells and an interesting solution for heterogeneous photocatalysis.     

Technological Research of a Clean Energy Router Based on Advanced Adiabatic Compressed Air Energy Storage System

As a fundamental infrastructure of energy supply for future society, energy Internet (EI) can achieve clean energy generation, conversion, storage and consumption in a more economic and safer way. This paper demonstrates the technology principle of advanced adiabatic compressed air energy storage system (AA-CAES), as well as analysis of the technical characteristics of AA-CAES. Furthermore, we propose an overall architectural scheme of a clean energy router (CER) based on AA-CAES. The storage and mutual conversion mechanism of wind and solar power, heating, and other clean energy were designed to provide a key technological solution for the coordination and comprehensive utilization of various clean energies for the EI. Therefore, the design of the CER scheme and its efficiency were analyzed based on a thermodynamic simulation model of AA-CAES. Meanwhile, we explored the energy conversion mechanism of the CER and improved its overall efficiency. The CER based on AA-CAES proposed in this paper can provide a reference for efficient comprehensive energy utilization (CEU) (93.6%) in regions with abundant wind and solar energy sources.     

In-Situ and In-Operando Experiments

How do we learn about the electronic and atomic characteristics of novel materials for efficient solar energy conversion (photovoltaics and water-splitting), energy storage (Li-ion batteries and multivalent-ion batteries), and efficient catalytic activity and selectivity in catalysis? The fundamental scientific problems that we plan to understand and ultimately control are: (1) efficient absorption-induced electron-hole pair formation and its separation at the complex interfaces; (2) bandgap, band levels, and band structure of earth abundant materials that are of crucial importance in electrochemical and photocatalytic applications.     

Computational efficient RCWA method for simulation of thin film solar cells

This paper presents a new implementation of the Fourier modal method to solve the Maxwell equations in nanostructured optoelectronic solid state devices such as thin-film solar cells. The proposed algorithm is suitable for structures with arbitrary spatial variation of the permittivity and it is based on an improved and computationally efficient approach that does not involve the calculation of eigenvalues. The two-dimensional (2-D) numerical simulator has been applied to model the light propagation in a thin film amorphous silicon solar cell in order to analyze the dependence of conversion efficiency on the morphology of the internal interfaces.     

Analysis and simulation of incident photon to current efficiency in dye sensitized solar cells

Conversion of solar energy into electricity is a challenging issue of today’s renewable energy. Electrochemical dye solar cells (DSC), based on nanostructured TiO₂ particles are a very promising class of photovoltaic devices [6]. The mechanism beyond the conversion of the light is quite different from any other solid state solar cell, resulting from the interplay of a fine tuning of the energy levels of the cell components and a delicate fabrication process. This complexity needs a reliable transport model, able to catch the device as a whole and applicable to experimental set up. We developed an extension of TiberCAD [7] code to simulate such kind of devices and compared the calculation with incident photon to current efficiency (IPCE) measurements.