InGaP/GaAs/Ge triple‐junction solar cells with ZnO nanowires

ZnO nanowire (NW) grown on triple‐junction (TJ) solar cells via the hydrothermal growth method to enhance efficiency is investigated. In this paper, experimental results indicate that TJ solar cells with ZnO NW as an antireflection (AR) coating have the lowest reflectance in the short wavelength spectrum, as compared with those of bare TJ solar cells (without AR coating) and solar cells with SiN_x and TiO₂/Al₂O₃ AR coatings. ZnO NW has the lowest light reflection among all experimental samples, especially in the range of ultraviolet to green light (300–500 nm). It was found that ZnO NW could enhance the conversion efficiency by 6.92%, as compared with the conventional TJ solar cell. In contrast, SiN_x and TiO₂/Al₂O₃ AR coatings could only enhance the conversion efficiency by 3.72% and 6.46% increase, respectively. The encapsulated results also suggested that the cell with ZnO NW coating could provide the best solar cell performances. Furthermore, all samples are measured at tilt angles of 0°–90° and results show that the solar cells with ZnO NW have the highest efficiency at all tilt angles. Furthermore, a small NW diameter increases light absorption. Copyright © 2012 John Wiley & Sons, Ltd.     

High efficiency CIGS based solar cells with electrodeposited ZnO:Cl as transparent conducting oxide front contact

In this paper high efficiency (up to 15.8%) Mo/Cu(In,Ga)Se₂/CdS/i‐ZnO solar cells terminated with an electrodeposited ZnO:Cl window layer are reported. The optoelectronic properties of these cells are comparable to reference cells terminated with standard sputtered ZnO:Al. The use of an electrochemical step, a low cost and easily up‐scalable method, in the fabrication process of this type of solar cell, opens the possibility to lower their production price and make them more competitive. The optimization involves a soft annealing treatment (T ≤ 150°C) under atmospheric conditions after the electrodeposition which improves the transparency of the ZnO:Cl layers in the infrared region, the short circuit current and the fill factor of the I–V curve. These changes are related to the increase of one order of magnitude (up to 5 × 10² Ω⁻¹·cm⁻¹) of the lateral conductivity of the electrochemical layer due to an improvement of the free carrier mobility. Copyright © 2010 John Wiley & Sons, Ltd.     

ZnO纳米线及其器件研究进展

介绍了氧化锌(ZnO)纳米线(NW)的性质,总结了ZnONW的气相法、液相法、模板生长法、自组装法等制备原理和方法,详细阐述了ZnONW基光电、压敏和气敏等纳米器件的研究现状,如在发光二极管、太阳能电池、紫外激光器、纳米发电机、气敏传感器的应用现状。分析了目前ZnONW器件实用化进程中难以解决的p型掺杂等方面的问题及其在荧光探针、稀磁半导体材料和自旋电子器件等方面的研究和应用趋势,指出今后的研究及发展方向主要将集中在ZnO缺陷形成及作用机理的研究,ZnONW荧光探针的制备及其在生物医学上的应用,不同结构的ZnO超晶格和多量子阱的制备及其在自旋电子器件中的应用。     

Dye-sensitized solar cells based on ZnO nanotetrapods

In this paper, we reviewed recent systematic studies of using ZnO nanotetrapods for photoanodes of dye-sensitized solar cells (DSSCs) in our group. First, the efficiency of power conversion was obtained by more than 3.27% by changes of conditions of dye loading and film thickness of ZnO nanotetrapod. Short-circuit photocurrent densities (Jsc) increased with the film thickness, Jsc would not be saturation even the film thickness was greater than 35 μm. The photoanode architecture had been charactered by good crystallinity, network forming ability, and limited electron-hopping interjunctions. Next, DSSCs with high efficiency was devised by infiltrating SnO2 nanoparticles into the ZnO nanotetrapods photoanodes. Due to material advantages of both constituents described as above, the composite photoanodes exhibited extremely large roughness factors (RFs), good charge collection, and tunable light scattering properties. By varying the composition of the composite photoanodes, we had achieved an efficiency of 6.31% by striking a balance between high efficiency of charge collection for SnO2 nanoparticles rich films and high light scattering ability for ZnO nanotetrapods rich films. An ultrathin layer of ZnO was found to form spontaneously on the SnO2 nanoparticles, which primarily was responsible for enhancing open-circuit photovoltage (Voc). We also identified that recombination in SnO2/ZnO composite films was mainly determined by ZnO shell condition on SnO2, whereas electron transport was greatly influenced by the morphologies and sizes of ZnO crystalline additives. Finally, we applied the composite photoanodes of SnO2 nanoparticles/ZnO nanotetrapods to flexible DSSCs by low temperature technique of "acetic acid gelation-mechanical press-ammonia activation." The efficiency has been achieved by 4.91% on ITO-coated polyethylenenaphtalate substrate. The formation of a thin ZnO shell on SnO2 nanoparticles, after ammonia activation, was also found to be critical to boosting Voc and to improving inter-particles contacts. Mechanical press, apart from enhancing film durability, also significantly improved charge collection. ZnO nanotetrapods had been demonstrated to be a better additive than ZnO particles for the improvement of charge collection in SnO2/ZnO composite photoanodes regardless of whether they were calcined.     

A High‐Reliability Kevlar Fiber‐ZnO Nanowires Hybrid Nanogenerator and its Application on Self‐Powered UV Detection

A microfiber‐nanowire hybrid structure is the fundamental component for a wearable piezoelectric nanogenerator (PENG) for harvesting body motion energy. Here, a novel approach combining surface coating and plasma etching techniques is reported to enhance the mechanical reliability of Kevlar microfiber‐ZnO nanowires (NWs) hybrid structure that is used for PENG. After treatment, the hybrid structure has dramatically improved high flexibility, robustness, and durability. On the basis of the coupled piezoelectric and semiconducting properties of ZnO, the processed Kevlar fibers covered with ZnO NWs are utilized to fabricate a 2D nanogenerator (2DNG). The open‐circuit voltage and short‐circuit current of the 2DNG are 1.8 mV and 4.8 pA, respectively. Furthermore, the 2DNG is successfully employed to quantitatively detect UV intensity from 0.2 to 1 mW cm^?2 as a self‐powered system.     

Room‐Temperature Tailoring of Vertical ZnO Nanoarchitecture Morphology for Efficient Hybrid Polymer Solar Cells

A ZnO nanoarchitecture, i.e., ZnO nanosheet (NS) framework, is demonstrated to be a promising electron acceptor and direct electron transport matrix for polymer‐inorganic hybrid solar cells. The ZnO NS framework is constructed on nanoneedles/indium tin oxide substrate via a room‐temperature chemical bath deposition (RT CBD). The framework morphology can be simply tailored by varying the concentration of precursor solution in the RT CBD. The ZnO nanoarchitecture with an appropriate free space between the NSs is consequently demonstrated to facilitate poly(3‐hexylthiophene) (P3HT) infiltration, resulting in superior interface properties, i.e., more efficient charge separation and less charge recombination, in the hybrid. Moreover, apart from the characteristics similar to the ZnO nanorod (NR) array, including vertical feature and single crystalline structure, the ZnO NS framework exhibits a slightly larger absorption edge and a faster electron transport rate. A notable efficiency of 0.88% is therefore attained in the ZnO NS‐P3HT hybrid solar cell, which is higher than that of the ZnO NR‐P3HT hybrid solar cell.     

Improvement in open circuit voltage of n‐ZnO/p‐Si solar cell by using amorphous‐ZnO at the interface

Several research groups are currently working on n‐ZnO/p‐Si heterojunction solar cell, and recently, Pietruszka et al [Sol. Energ. Mat. Sol. Cells 147 (2016) 164‐170] has reported the highest efficiency of 7.1% for this structure. The main challenge is to enhance the open circuit voltage up to theoretically predicted value of >0.6 V. This paper reports >20% improvement in open circuit voltage of n‐ZnO/p‐Si solar cell by depositing amorphous‐ZnO at the interface at room temperature that possibly improves the passivation and/or avoids oxide formation at the interface during ZnO deposition. Two other materials, aluminum nitride and amorphous‐Si, have also been used as buffer layers to evaluate their effect on suppression of interface states. Furthermore, additional advantage of ZnO as an antireflector has been experimentally verified for different thicknesses of ZnO film.     

Transparent,Double‐Sided,ITO‐Free,Flexible Dye‐Sensitized Solar Cells Based on Metal Wire/ZnO Nanowire Arrays

Transparent, double‐sided, flexible, ITO‐free dye‐sensitized solar cells (DSSCs) are fabricated in a simple, facile, and controllable way. Highly ordered, high‐crystal‐quality, high‐density ZnO nanowire arrays are radially grown on stainless steel, Au, Ag, and Cu microwires, which serve as working electrodes. Pt wires serve as the counter electrodes. Two metal wires are encased in electrolyte between two poly(ethylene terephthalate) (PET) films (or polydimethylsiloxane (PDMS) films) to render the device both flexible and highly transparent. The effect of the dye thickness on the photovoltaic performance of the DSSCs as a function of dye‐loading time is investigated systematically. Shorter dye‐loading times lead to thinner dye layers and better device performance. A dye‐loading time of 20 min results in the best device performance. An oxidation treatment of the metal wires is developed effectively to avoid the galvanic‐battery effect found in the experiment, which is crucial for real applications of double‐metal‐wire DSSC configurations. The device shows very good transparency and can increase sunlight use efficiency through two‐sided illumination. The double‐wire DSSCs remain stable for a long period of time and can be bent at large angles, up to 107°, reversibly, without any loss of performance. The double‐wire‐PET, planar solar‐cell configuration can be used as window stickers and can be readily realized for large‐area‐weave roll‐to‐roll processing.     

Bifacial concentrator Ag‐free crystalline n‐type Si solar cell

We report results obtained using an innovative approach for the fabrication of bifacial low‐concentrator thin Ag‐free n‐type Cz‐Si (Czochralski silicon) solar cells based on an indium tin oxide/(p⁺nn⁺)Cz‐Si/indium fluorine oxide structure. The (p⁺nn⁺)Cz‐Si structure was produced by boron and phosphorus diffusion from B‐ and P‐containing glasses deposited on the opposite sides of n‐type Cz‐Si wafers, followed by an etch‐back step. Transparent conducting oxide (TCO) films, acting as antireflection electrodes, were deposited by ultrasonic spray pyrolysis on both sides. A copper wire contact pattern was attached by low‐temperature (160°C) lamination simultaneously to the front and rear transparent conducting oxide layers as well as to the interconnecting ribbons located outside the structure. The shadowing from the contacts was ~4%. The resulting solar cells, 25 × 25 mm² in dimensions, showed front/rear efficiencies of 17.6–17.9%/16.7–17.0%, respectively, at one to three suns (bifaciality of ~95%). Even at one‐sun front illumination and 20–50% one‐sun rear illumination, such a cell will generate energy approaching that produced by a monofacial solar cell of 21–26% efficiency. Copyright © 2014 John Wiley & Sons, Ltd.     

Improved performance in ZnO/CdS/CuGaSe2 thin‐film solar cells

We report the growth and characterization of improved efficiency wide‐bandgap ZnO/CdS/CuGaSe₂ thin‐film solar cells. The CuGaSe₂ absorber thickness was intentionally decreased to better match depletion widths indicated by drive‐level capacitance profiling data. A total‐area efficiency of 9·5% was achieved with a fill factor of 70·8% and a V_oc of 910 mV. Published in 2003 by John Wiley & Sons, Ltd.     

基于ZnO纳米片/纳米球复合结构光阳极的染料敏化太阳电池

将电沉积和溶剂热方法制备的ZnO纳米片阵列和ZnO纳米球组装成ZnO纳米片/纳米球复合结构光阳极,并应用 透射电镜(TEM)、扫描电镜(SEM)、X射线衍射仪(XRD)对合成产物的形貌和晶相进行表征.染料敏化太阳电池性能测试表 明,与单一光阳极结构的ZnO纳米片基电池相比,基于更大比表面积和更强光散射效应的ZnO纳米片...     

Sn‐catalyzed silicon nanowire solar cells with 4.9% efficiency grown on glass

We present a single pump‐down process to texture hydrogenated amorphous silicon solar cells. Mats of p‐type crystalline silicon nanowires were grown to lengths of 1 µm on glass covered with flat ZnO using a plasma‐assisted Sn‐catalyzed vapor‐liquid‐solid process. The nanowires were covered with conformal layers of intrinsic and n‐type hydrogenated amorphous silicon and a sputtered layer of indium tin oxide. Each cell connects in excess of 10⁷ radial junctions over areas of 0.126 cm². Devices reach open‐circuit voltages of 0.8 V and short‐circuit current densities of 12.4 mA cm⁻², matching those of hydrogenated amorphous silicon cells deposited on textured substrates. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly‐efficient Cd‐free CuInS2 thin‐film solar cells and mini‐modules with Zn(S,O) buffer layers prepared by an alternative chemical bath process

Recent progress in fabricating Cd‐ and Se‐free wide‐gap chalcopyrite thin‐film solar devices with Zn(S,O) buffer layers prepared by an alternative chemical bath process (CBD) using thiourea as complexing agent is discussed. Zn(S,O) has a larger band gap (E_g = 3·6–3·8 eV) than the conventional buffer material CdS (E_g = 2·4 eV) currently used in chalcopyrite‐based thin films solar cells. Thus, Zn(S,O) is a potential alternative buffer material, which already results in Cd‐free solar cell devices with increased spectral response in the blue wavelength region if low‐gap chalcopyrites are used. Suitable conditions for reproducible deposition of good‐quality Zn(S,O) thin films on wide‐gap CuInS₂ (‘CIS’) absorbers have been identified for an alternative, low‐temperature chemical route. The thickness of the different Zn(S,O) buffers and the coverage of the CIS absorber by those layers as well as their surface composition were controlled by scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray excited Auger electron spectroscopy. The minimum thickness required for a complete coverage of the rough CIS absorber by a Zn(S,O) layer deposited by this CBD process was estimated to ∼15 nm. The high transparency of this Zn(S,O) buffer layer in the short‐wavelength region leads to an increase of ∼1 mA/cm² in the short‐circuit current density of corresponding CIS‐based solar cells. Active area efficiencies exceeding 11·0% (total area: 10·4%) have been achieved for the first time, with an open circuit voltage of 700·4 mV, a fill factor of 65·8% and a short‐circuit current density of 24·5 mA/cm² (total area: 22·5 mA/cm²). These results are comparable to the performance of CdS buffered reference cells. First integrated series interconnected mini‐modules on 5 × 5 cm² substrates have been prepared and already reach an efficiency (active area: 17·2 cm²) of above 8%. Copyright © 2006 John Wiley & Sons, Ltd.     

CuOx/a‐Si:H heterojunction thin‐film solar cell with an n‐type µc‐Si:H depletion‐assisting layer

We showed that thin n‐type CuO_x films can be deposited by radio‐frequency magnetron reactive sputtering and demonstrated the fabrication of n‐CuO_x/intrinsic hydrogenated amorphous silicon (i‐a‐Si:H) heterojunction solar cells (HSCs) for the first time. A highly n‐doped hydrogenated microcrystalline Si (n‐µc‐Si:H) layer was introduced as a depletion‐assisting layer to further improve the performance of n‐CuO_x/i‐a‐Si:H HSCs. An analysis of the external quantum efficiency and energy‐band diagram showed that the thin depletion‐assisting layer helped establish sufficient depletion and increased the built‐in potential in the n‐CuO_x layer. The fabricated HSC exhibited a high open‐circuit voltage of 0.715 V and an efficiency of 4.79%. Copyright © 2015 John Wiley & Sons, Ltd.     

Properties of 19.2% efficiency ZnO/CdS/CuInGaSe2 thin‐film solar cells

We report the growth and characterization of record‐efficiency ZnO/CdS/CuInGaSe₂ thin‐film solar cells. Conversion efficiencies exceeding 19% have been achieved for the first time, and this result indicates that the 20% goal is within reach. Details of the experimental procedures are provided, and material and device characterization data are presented. Published in 2003 by John Wiley & Sons, Ltd.     

Achievement of 17.9% efficiency in 30 × 30 cm2 Cu(In,Ga)(Se,S)2 solar cell sub‐module by sulfurization after selenization with Cd‐free buffer

We have achieved 17.9% efficiency in a 30 × 30 cm² Cu(In,Ga)(Se,S)₂ solar cell sub‐module prepared by selenization and sulfurization processes with a Cd‐free buffer. The development of an absorber layer, transparent conducting oxide window layer, and module design was the key focus. This permitted 1.8% higher efficiency than our last experimental result. The quantity and the injection time of the sodium were controlled, resulting in higher open circuit voltage (V_oc) and short circuit current (J_sc). In order to increase J_sc, we changed the thickness of the window layer. Boron‐doped zinc oxide was optimized for higher transmittance without reducing the fill factor. The uniformity of each layer was improved, and patterns were optimized for each module. Therefore, V_oc, J_sc, and FF could be theoretically improved on the reported results of, respectively, 20 mV, 2 mA/cm², and 1.4%. The module's efficiency was measured at the Korea Test Laboratory to compare with the data obtained in‐house. Various analyses were performed, including secondary ion mass spectroscopy, photoluminescence, quantum efficiency, solar simulator, and UV–vis spectrometry, to measure the cell's depth profile, carrier lifetime, external quantum efficiency, module efficiency, and transmittance, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

III‐V concentrator solar cell reliability prediction based on quantitative LED reliability data

III‐V Multi Junction (MJ) solar cells based on Light Emitting Diode (LED) technology have been proposed and developed in recent years as a way of producing cost‐competitive photovoltaic electricity. As LEDs are similar to solar cells in terms of material, size and power, it is possible to take advantage of the huge technological experience accumulated in the former and apply it to the latter. This paper analyses the most important parameters that affect the operational lifetime of the device (crystalline quality, temperature, current density, humidity and photodegradation), taking into account experience on the reliability of LEDs. Most of these parameters are less stressed for a III‐V MJ solar cell working at 1000 suns than for a high‐power LED. From this analysis, some recommendations are extracted for improving the long‐term reliability of the solar cells. Compared to high‐power LEDs based on compound semiconductors, it is possible to achieve operational lifetimes higher than 10⁵ hours (34 years of real‐time operation) for III‐V high‐concentration solar cells. Copyright © 2007 John Wiley & Sons, Ltd.     

激光刻蚀柔性薄膜太阳电池复合背反射层的研究

柔性聚酯膜衬底薄膜电池通过激光刻蚀等工艺形成集成串联,激光刻蚀柔性薄膜太阳电池复合背反射层(Ag/ZnO)是其中的重要工艺。首先对聚酰亚胺(PI)、Ag、ZnO材料的光学特性进行了分析,然后采用1 064nm脉冲激光与532nm脉冲激光分别对柔性薄膜太阳电池复合背反射层进行刻蚀研究。通过改变重复频率、激光功率、扫描速度和焦点位置等参数,分析了激光刻蚀物理机制,获得了好的刻蚀效果。结果表明,1 064nm纳秒脉冲激光更适合刻蚀柔性PI衬底复合背反射层Ag/ZnO,在激光功率860mW、刻蚀速度800mm/s和重复频率50kHz下,获得了底部平整、两侧无尖峰的刻线,刻线宽为32μm,满足柔性薄膜太阳电池集成串联组件的制备工艺要求。     

Design and development of an integrated device consisting of an independent solar cell with electrical storage capacity

A thin film‐integrated device was constructed consisting of photovoltaic layers combined with additional layers to store charge in real time within the same device. In our design, a dye‐sensitized solar cell and capacitor layers are integrated by a double‐anodized titanium plate, which consists of TiO₂ nanotubes grown on either side by electrochemical anodization. The combination device can act either as an independent solar cell, a capacitor, or as a solar cell/capacitor device. The results presented here illustrate the capacitive behavior of high surface area nanotubular metal oxide films, with an achieved capacitance of 140 μF cm⁻². Copyright © 2012 John Wiley & Sons, Ltd.     

A high‐efficiency LPE GaAs solar cell at concentrations ranging from 2000 to 4000 suns

III–V solar cells for terrestrial concentration applications are currently becoming of greater and greater interest. From our experience, concentrations higher than 1000 suns are required with these cells to reduce PV electricity cost to such an extent that this alternative could become cost competitive. In this paper, a single‐junction p/n GaAs solar cell, with efficiencies of 23ċ8 and 22ċ5% at concentration ratios of 2700 and 3600 suns respectively, is presented. This GaAs solar cell is well suited for use with non‐imaging optical concentrators, which possess a large aperture angle. Low‐temperature liquid phase epitaxy (LTLPE) has been the growing technique for the semiconductor structure as an attempt to use a simplified, cheap and clean technique, within a renewable energy perspective. The GaAs solar cell presented is compared with the highest efficiency tandem solar cells at concentration levels exceeding 1000 suns. The GaAs solar cell performance maintains high efficiencies up to 4000 suns, while tandem cells seem to drop very quickly after reaching their maximum. Therefore, single‐junction GaAs solar cells are a good candidate for operating at very high concentrations, and LPE is able to supply these high‐quality solar cells to work within terrestrial concentration systems, the main objective of which is the reduction of PV electricity costs. Copyright © 2003 John Wiley & Sons, Ltd.