Improved photovoltaic performance of silicon nanowire/organic hybrid solar cells by incorporating silver nanoparticles

Silicon nanowire (SiNW) arrays show an excellent light-trapping characteristic and high mobility for carriers. Surface plasmon resonance of silver nanoparticles (AgNPs) can be used to increase light scattering and absorption in solar cells. We fabricated a new kind of SiNW/organic hybrid solar cell by introducing AgNPs. Reflection spectra confirm the improved light scattering of AgNP-decorated SiNW arrays. A double-junction tandem structure was designed to manufacture our hybrid cells. Both short-circuit current and external quantum efficiency measurements show an enhancement in optical absorption of organic layer, especially at lower wavelengths.     

Effects of Annealing Conditions of Electrodes on the Photovoltaic Properties of Sintered Cadmium Sulfide/Cadmium Telluride Solar Cells

Polycrystalline n -CdS/ p -CdTe solar cells with a commerical carbon paint on the p -CdTe layer and an In-Ag paint on the n -CdS layer were fabricated by a coating and sintering method. Electrical properties of the conducting paints and solar cell parameters of the heterojunction solar cells were investigated as a function of electrode annealing conditions. The sintered CdS/CdTe solar cells whose electrode contacts were annealed at 350°C for 10 min in nitrogen showed maximum values of short-circuit current density, fill factor, and solar efficiency. Commercial carbon and silver paints can be used as electrodes to fabricate sintered CdS/CdTe solar cells with efficiency over 10%.     

Silver nanowire-based transparent,flexible, and conductive thin film

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles.     

The effect of nanowire length and diameter on the properties of transparent, conducting nanowire films

This article describes how the dimensions of nanowires affect the transmittance and sheet resistance of a random nanowire network. Silver nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver nanowire films. Finite-difference time-domain calculations were used to determine the effect of nanowire diameter, overlap, and hole size on the transmittance of a nanowire network. For individual nanowires with diameters greater than 50 nm, increasing diameter increases the electrical conductance to optical extinction ratio, but the opposite is true for nanowires with diameters less than this size. Calculations and experimental data show that for a random network of nanowires, decreasing nanowire diameter increases the number density of nanowires at a given transmittance, leading to improved connectivity and conductivity at high transmittance (>90%). This information will facilitate the design of transparent, conducting nanowire films for flexible displays, organic light emitting diodes and thin-film solar cells.     

Solution-processed germanium nanowire-positioned Schottky solar cells

Germanium nanowire (GeNW)-positioned Schottky solar cell was fabricated by a solution process. A GeNW-containing solution was spread out onto asymmetric metal electrodes to produce a rectifying current flow. Under one-sun illumination, the GeNW-positioned Schottky solar cell yields an open-circuit voltage of 177 mV and a short-circuit current of 19.2 nA. Schottky and ohmic contacts between a single GeNW and different metal electrodes were systematically investigated. This solution process may provide a route to the cost-effective nanostructure solar architecture.     

Silver front electrode grids for ITO-free all printed polymer solar cells with embedded and raised topographies, prepared by thermal imprint, flexographic and inkjet roll-to-roll processes

Semitransparent front electrodes for polymer solar cells, that are printable and roll-to-roll processable under ambient conditions using different approaches, are explored in this report. The excellent smoothness of indium-tin-oxide (ITO) electrodes has traditionally been believed to be difficult to achieve using printed front grids, as surface topographies accumulate when processing subsequent layers, leading to shunts between the top and bottom printed metallic electrodes. Here we demonstrate how aqueous nanoparticle based silver inks can be employed as printed front electrodes using several different roll-to-roll techniques. We thus compare hexagonal silver grids prepared using either roll-to-roll inkjet or roll-to-roll flexographic printing. Both inkjet and flexo grids present a raised topography and were found to perform differently due to only the conductivity of the obtained silver grid. The raised topographies were compared with a roll-to-roll thermally imprinted grid that was filled with silver in a roll-to-roll process, thus presenting an embedded topography. The embedded grid and the flexo grid were found to perform equally well, with the flexographic technique currently presenting the fastest processing and the lowest silver use, whereas the embedded grid presents the maximally achievable optical transparency and conductivity. Polymer solar cells were prepared in the same step, using roll-to-roll slot-die coating of zinc oxide as the electron transport layer, poly-3-hexylthiophene:phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM) as the active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the top electrode, along with a flat bed screen printed silver grid. The power conversion efficiency (PCE) obtained for large area devices (6 cm(2)) was 1.84%, 0.79% and 1.72%, respectively, for thermally imprinted, inkjet and flexographic silver grids, tested outside under the real sun. Central to all three approaches was that they employed environmentally friendly solvents, i.e. water based nanoparticle silver inks.     

Printed silver nanowire antennas with low signal loss at high-frequency radio

Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.     

Organic electrochemical transistors based on a dielectrophoretically aligned nanowire array

In this study, we synthesized an organic electrochemical transistor (OECT) using dielectrophoresis of a carbon nanotube-Nafion (CNT-Nafion) suspension. Dielectrophoretically aligned nanowires formed a one-dimensional submicron bundle between triangular electrodes. The CNT-Nafion composite nanowire bundles showed p-type semiconductor characteristics. The drain-source current decreased with increasing gate voltage. The nanowire bundles showed potential as pH sensor because the drain-source current ratio varied linearly according to the gate voltage in pH buffers.     

Nanostructured conformal hybrid solar cells: a promising architecture towards complete charge collection and light absorption

We introduce hybrid solar cells with an architecture consisting of an electrodeposited ZnO nanorod array (NRA) coated with a conformal thin layer (<50 nm) of organic polymer-fullerene blend and a quasi-conformal Ag top contact (Thin/NR). We have compared the performance of Thin/NR cells to conventional hybrid cells in which the same NRAs are completely filled with organic blend (Thick/NR). The Thin/NR design absorbs at least as much light as Thick/NR cells, while charge extraction is significantly enhanced due to the proximity of the electrodes, resulting in a higher current density per unit volume of blend and improved power conversion efficiency. The NRAs need not be periodic or aligned and hence can be made very simply.     

Preparation of polyaniline nanowire arrayed electrodes for electrochemical supercapacitors

Polyaniline (PANI) nanowire arrayed electrodes were successfully synthesized by means of anodic deposition technique using the membrane-template synthesis route. The desired three-dimensional architecture of PANI nanowire arrayed electrodes was characterized with field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) techniques. It was found that the co-deposition nanowires were regular size and continuous with an average diameter of about 30 nm, and the nanowires have an amorphous nature. The electrochemical characterization was performed in 2 M H₂SO₄ aqueous solution. The capacitance of the PANI nanowire arrayed electrode at a charge–discharge current density of 5 Ag⁻¹ is 1142 Fg⁻¹. The nanowire arrayed electrodes showed an excellent capacitive ability for the facility of electrolyte penetration, the ease of proton exchange/diffusion and the metallic conductivity of PANI nanowire arrayed electrodes.     

Phosphonate-functionalized polyfluorene and its application in organic optoelectronic devices

Conjugated polar polymers, in which the conjugated backbones are chemically anchored with functional polar side groups, can be processed with water/alcohol solvents, and thus multilayered device architectures can be easily realized via sequential solution processing of the toluene-soluble emissive polymer and alcohol-soluble electron-transporting polymer without intermixing. Regarding their use in organic optoelectronic devices, the success in achieving efficient charge injection and intimate contact between metal electrodes and organic semiconductors is very vital for enhancing the device performance. In this short review, it gives a brief review to neutral alcohol-soluble phosphonate-functionalized polyfluorene, mainly concerning the electronic structure at the phosphonate-functionalized polyfluorene/aluminum cathode interface and its successful application in multilayered polymer optoelectronic devices including polymer light-emitting diodes and polymer solar cells.     

High-performance and low platinum loading electrodeposited-Pt counter electrodes for dye-sensitized solar cells

This study demonstrates platinum (Pt) counter electrodes with low charge-transfer resistance (R_ct), low Pt loading and high active surface area can be obtained within 30 s by using the direct-current deposition in the presence of 3-(2-aminoethylamino)propyl-methyldimethoxysilane (Me-EDA-Si) as an additive. The addition of appropriate Me-EDA-Si can not only enhance the current efficiency but also inhibit the growth of semicircle-like grains, thus resulting in Pt electrode with high active surface area. Consequently, the dye-sensitized solar cells (DSSCs) fabricated with so-prepared Pt electrodes exhibited cell efficiency of 7.39% while 0.01 vol% Me-EDA-Si was added, which is much superior to that with sputtered-Pt electrodes under the same assembly conditions.     

Photovoltaic solar electrochemical oxidation (PSEO) for treatment of lignosulfonate wastewater

BACKGROUND: Under the current global energy scenario, the need for self‐sustainable processes is encouraged. The photovoltaic solar powered electrochemical oxidation (PSEO) process has been developed to remove the organic matter from a lignosulfonate wastewater. RESULTS: An electrochemical reactor using boron‐doped diamond electrodes, in a batch configuration, is directly supplied with current from a set of photovoltaic solar modules. Experimental results show that the process can oxidize about 90% of the total organic carbon (TOC) of the organic matter in the wastewater under the described operating conditions. CONCLUSION: The technical suitability of the PSEO process has been demonstrated. A model to relate solar irradiance and electrical current was applied and used in a kinetic expression which depends on solar irradiance to describe the removal of TOC. Copyright © 2010 Society of Chemical Industry     

Electrodeposition of CdSe coatings on ZnO nanowire arrays for extremely thin absorber solar cells

We report on electrodeposition of CdSe coatings onto ZnO nanowire arrays and determine the effect of processing conditions on material properties such as morphology and microstructure. CdSe-coated ZnO nanowire arrays have potential use in extremely thin absorber (ETA) solar cells, where CdSe absorbs visible light and injects photoexcited electrons into the ZnO nanowires. We show that room-temperature electrodeposition enables growth of CdSe coatings that are highly crystalline, uniform, and conformal with precise control over thickness and microstructure. X-ray diffraction and transmission electron microscopy show nanocrystalline CdSe in both hexagonal and cubic phases with grain size ∼5 nm. Coating morphology depends on electrodeposition current density. Uniform and conformal coatings were achieved using moderate current densities of ∼2 mA cm⁻² for nanowires with roughness factor of ∼10, while lower current densities resulted in sparse nucleation and growth of larger, isolated islands. Electrodeposition charge density controls the thickness of the CdSe coating, which was exploited to investigate the evolution of the morphology at early stages of nucleation and growth. UV–vis transmission spectroscopy and photoelectrochemical solar cell measurements demonstrate that CdSe effectively sensitizes ZnO nanowires to visible light.     

基于钯纳米线阵列修饰电极的抗坏血酸电化学研究

以氧化铝模板为基础,采用电化学沉积方法制备了钯纳米线阵列修饰金电极。电化学方法研究了该修饰电极对抗坏血酸电化学行为,实验结果表明,抗坏血酸在高度有序的钯纳米线饰电极表面出现显著的氧化峰。氧化峰的峰电流与抗坏血酸的浓度在4.0×10-4~3.15×10-3 mol/L范围内有良好的线性关系,检测限可达1×10-4 mol/L。该电极制备方便,有良好的灵敏度和稳定性。     

太阳能电池无铅导电电极的制备及电性能研究

以Bi2O3、B2O3和SiO2为主要原料制备无铅玻璃粘合剂,将其与导电银(Ag)粉、Al2O3、MnO2等无机添加剂和α-松油醇等有机载体进行混合制备无铅导电银浆,在800℃的温度下烧结20s形成Ag电极。采用四点探针法测量Ag电极电阻率ρ,通过SEM观察其断面形貌并用Keithley2400数字源表测定电池的相关性能参数,研究了Ag电极中导电Ag粉含量对电极性能的影响,确定了无铅导电Ag浆的质量配比为:导电银粉75%,玻璃粘合剂(Glass frit,GF)4%,无机添加剂1%,有机载体20%时,Ag电极的电性能趋于最佳。     

Radial n-i-p structure SiNW-based microcrystalline silicon thin-film solar cells on flexible stainless steel

Radial n-i-p structure silicon nanowire (SiNW)-based microcrystalline silicon thin-film solar cells on stainless steel foil was fabricated by plasma-enhanced chemical vapor deposition. The SiNW solar cell displays very low optical reflectance (approximately 15% on average) over a broad range of wavelengths (400 to 1,100 nm). The initial SiNW-based microcrystalline (μc-Si:H) thin-film solar cell has an open-circuit voltage of 0.37 V, short-circuit current density of 13.36 mA/cm², fill factor of 0.3, and conversion efficiency of 1.48%. After acid treatment, the performance of the modified SiNW-based μc-Si:H thin-film solar cell has been improved remarkably with an open-circuit voltage of 0.48 V, short-circuit current density of 13.42 mA/cm², fill factor of 0.35, and conversion efficiency of 2.25%. The external quantum efficiency measurements show that the external quantum efficiency response of SiNW solar cells is improved greatly in the wavelength range of 630 to 900 nm compared to the corresponding planar film solar cells.     

Preparation and Application of Nano-composite Poly(vinyl alcohol) Gel Electrolyte in Electrochemical Capacitor

A nano-composite polymer gel electrolyte was prepared using titanium oxide nanowire, poly(vinyl alcohol) (PVA), lithium salt and organic solvent N-methyl-2-pyrrolidone (NMP). The obtained electrolyte has the potential for application in electrochemical capacitor, the PVA in it is in an amorphous state. The ionic conductivities of electrolytes increased after addition of the nanowire, and the electrolyte with 3%(w) of nanowire exhibited the highest ionic conductivity of 3.2 mS/cm at 20℃, as measured by electrochemical impedance spectroscopy. The temperature dependence of the conductivity was found to be in agreement with the Arrhenius equation. Functioning as separator and electrolyte, this nano-composite PVA gel electrolyte was used to assemble the electrochemical capacitor with active carbon film as electrodes. The compositing of nanowire may extend the life of electrochemical capacitors as they keep more than 90% of their capacitance after 5000 cycles of charging and discharging.     

The current distribution and shape change of zinc electrodes in secondary silver-zinc cells

The current and potential distributions of zinc electrodes in secondary zinc-silver oxide cells during cycling were studied using a sectioned electrode technique. The shape change occurring in zinc electrodes resulting from cell cycling was examined. The zinc electrodes used for this study were of a conventional type of design and were fabricated by a slurry paste method. The positive electrodes used were sectioned silver oxide electrodes, each of which comprised nine sections of sintered silver plates. The results indicate that, by adding a layer of non-woven fabric treated with Fe₂O₃ to the edge sections of the electrode separator system, the uniformity of the current and potential distributions on the zinc electrodes during cell cycling can be improved, and the zinc electrode shape change resulting from cell cycling can be effectively suppressed.     

Electrodeposited Pt for cost-efficient and flexible dye-sensitized solar cells

Pt electrodes were prepared by direct and pulse current electrodeposition for use as counter electrodes in dye-sensitized solar cells. Scanning electron microscope and transmission electron microscope images confirmed the formation of uniform Pt nanoclusters of ∼40 nm composed of 3 nm nanoparticles, when the pulse current electrodeposition method was used, as opposed to the dendritic growth of Pt by the results from direct current electrodeposition. By applying pulse electrodeposited Pt which has a 1.86 times higher surface area compared to direct current electrodeposited Pt, short-circuit current and conversion efficiency were increased from 10.34 to 14.11 mA/cm² and from 3.68 to 5.03%, respectively. In addition, a flexible solar cell with a pulse current electrodeposited Pt counter electrode with a conversion efficiency of 0.86% was demonstrated.