Efficient dye-sensitized solar cells from mesoporous zinc oxide nanostructures sensitized by N719 dye

Dye-sensitized solar cells (DSCs) have attracted a great deal of attention due to their low-cost and high power conversion efficiencies.They usually utilize an interconnected nanoparticle layer of TiO2 as the electron transport medium.From the fundamental point of view,faster mobility of electrons in ZnO is expected to contribute to better performance in DSCs than TiO2,though the actual practical situation is quite the opposite.In this research,we addressed this problem by first applying a dense layer of ZnO on FTO followed by a mesoporous layer of interconnected ZnO nanoparticle layer,both were prepared by spray pyrolysis technique.The best cell shows a power conversion efficiency of 5.2％ when the mesoporous layer thickness is 14μm and the concentration of the N719 dye in dye coating solution is 0.3 mM,while a cell without a dense layer shows 4.2％ under identical conditions,The surface concentration of dye adsorbed in the cell with a dense layer and that without a dense layer are 5.00 × 10-7 and 3.34 × 10-7 mol/cm2,respectively.The cell with the dense layer has an electron lifetime of54.81 ms whereas that without the dense layer is 11.08 ms.As such,the presence of the dense layer improves DSC characteristics ofZnO-based DSCs.     

Enhanced electron injection/transportation by surface states increment in mesoporous TiO2 dye-sensitized solar cells

A strategy of surface modification to the mesoporous TiO2 photoanode with hydrochloric acid treatment was used in this study, and it was found that short circuit current and photovoltaic efficiency of dyesensitized solar cells (DSSCs) were increased by 5.5% and 8.9% respectively. The improvement was attributed to the reduced impedances in the TiO2 film and at the TiO2/dye/electrolyte interface. It was showed that the increased surface electronic states could remarkably prolong electron lifetime, which was responsible for the reduction of impedances. Under these quasi-continuous states in mesoporous structure, the electron injection/transportation can be notably facilitated, which will be beneficial for the DSSC performance.     

晶体硅太阳电池的双层结构钝化膜研究

针对目前基于p型硅片制备的单结太阳电池进一步提高表面钝化膜生产效率,利用氮化硅(SiNx)薄膜良好的钝化效果与价格低廉的二氧化钛(TiO2)膜,降低SiNx镀膜厚度减薄对少子寿命的影响。在单晶硅片表面先用PECVD法沉积SiNx薄膜,然后用热喷涂沉积TiO2薄膜。对比测试了热喷涂沉积TiO2薄膜前后电池的性能,结果表明在SiNx膜上增加TiO2膜层后少子寿命明显提高,这可能是TiO2膜结构内存在固定正电荷所致。这种双层结构封装后的太阳电池显示出了较好的光学与电学性能,对进一步改进太阳电池性能具有重要参考价值。     

Improved air stability of PbS-sensitized solar cell by incorporating ethanedithiol during spin-assisted successive ionic layer adsorption and reaction

We fabricated all solid-state PbS-sensitized solar cells by the repeated step-by-step spin-coating of Pb(NO₃)₂, Na₂S, and ethanedithiol (EDT) solution on mesoporous TiO₂ (mp-TiO₂) films. Incorporating EDT molecules into the PbS nanoparticles during the spin-assisted successive ionic layer adsorption and reaction (SILAR) process greatly improved the stability of the device in air and its efficiency owing to the improved charge injection and surface passivation because the EDT molecules prevent the overgrowth and oxidation of the PbS nanoparticles during the layer-by-layer coating of the EDT molecules.     

色散效应对钝化硅太阳电池减反射膜系设计的影响

在考虑折射率色散效应基础上,以加权平均反射率作为评价函数,通过智能优化算法对空间硅太阳电池减反射膜进行优化设计,得到了最佳的膜厚参数,并与不考虑色散下设计的减反射膜进行了比较。对MgF2/TiO2,SiO2/TiO2双层减反射膜,与不考虑色散情形相比,考虑色散下优化后的最小加权平均反射率分别减小了36.6%和37.6%;对具有厚度为15 nm的SiO2钝化层的硅太阳电池的MgF2/TiO2,SiO2/TiO2减反射膜重新优化设计,与不考虑色散情形相比,考虑色散下优化后的最小加权平均反射率分别减小了43.9%和33.7%;对具有不同厚度钝化层的空间硅太阳电池,在考虑色散下进行了减反射膜的优化设计。结果发现,随着钝化层厚度的增加,所得减反射膜的最小加权平均反射率也随之增大,减反射效果越来越弱。最后,在考虑与未考虑色散情形下,将钝化层膜厚也作为反演参量后重新设计。结果表明:在色散情形下所设计的减反射膜更佳,对于MgF2/TiO2/SiO2（钝化层）膜系,最佳膜厚参量为d1（MgF2）=97.6 nm,d2（TiO2）=40.2 nm,d3（SiO2）=4.9 nm;对于SiO2/TiO2/SiO2（钝化层）,最佳膜厚参量为d1（SiO2）=85.1 nm,d2（TiO2）=43.4 nm,d3（SiO2）=1.8 nm。     

Conformal Nano‐Sized Inorganic Coatings on Mesoporous TiO2 Films for Low‐Temperature Dye‐Sensitized Solar Cell Fabrication

Here, a new method based on sol–gel electrophoretic deposition to produce uniform high‐quality inorganic conformal coatings on mesoporous nano‐particulate films is presented. This novel sol preparation method allows for very fine control of the coating properties, thus inducing new adjustable functionalities to these electrodes. It is shown that the deposition of an amorphous TiO₂ and/or MgO shell onto photoanodes used in dye‐sensitized solar cells (DSSCs) improves their light‐to‐electric‐power conversion efficiency without the need for sintering. It is proposed that the amorphous TiO₂ coating improves the electronic inter‐particle connection and passivates the surface states. The insulating MgO coating further reduces the electron transfer from the conduction band into the electrolyte while the electron injection from the excited dye state remains unperturbed for thin coatings. Using a low‐temperature method for DSSC production on plastic substrates, a maximum efficiency of 6.2% applying pressure together with an optimized TiO₂ coating is achieved. For systems that cannot be pressed a conversion efficiency of 5.1% is achieved using a double shell TiO₂/MgO coating.     

一种柔性染料敏化太阳能电池的初步研究

染料敏化太阳能电池(DSSC)与商用硅电池相比,由于具有转化效率较高、制作成本低等一系列优点,近年来已受到人们的广泛关注.简要介绍了DSSC太阳能电池的结构和基本原理,重点分析了DSSC太阳能电池的关键组成和影响光电转化效率的因素.采用胶带涂覆法在柔性ITO衬底上制备了多孔纳米TiO2薄膜,通过给其配置相应的染料和电解...     

Double-layered silicon nitride antireflection coatings for multicrystalline silicon solar cells

Silicon nitride coating possesses both optical antireflection and electrical passivation effects for crystalline silicon solar cells. In this work, we employed a double-layered silicon nitride coating consisting of a top layer with a lower refractive index and a bottom layer (contacting the silicon wafer) with a higher refractive index for multicrystalline silicon solar cells. Double-layered silicon nitride coating provides a lower optical reflection and better surface passivation than those of single-layered silicon nitride. Details for optimizing the double-layered silicon nitride coating are presented. In order to get statistical conclusions, we fabricated a large number of multicrystalline silicon solar cells using the production line for both the double-layered and single-layered cell types. It was statistically demonstrated that the double-layered silicon nitride coating provided a consistent enhancement in the photovoltaic performance of multicrystalline silicon solar cells over those of the single-layered silicon nitride coating.     

Transparent conductive oxide‐less back contact dye‐sensitized solar cells using cobalt electrolyte

Transparent conductive oxide‐less (TCO‐less) dye‐sensitized solar cells (DSSCs) have been fabricated and characterized using nanoporous TiO₂‐coated stainless steel metal mesh as flexible photoanode and cobalt bipyridyl complex (Co(bpy))‐based one electron redox shuttle electrolyte. Attempts have been made towards enhancing the efficiency of TCO‐less DSSCs to match with their TCO‐based DSSC counterparts. It has been found that surface protection of metal mesh is highly required for enhancing the efficiency of TCO‐less DSSCs specially using cobalt electrolytes as confirmed by dark current–voltage characteristics. Photocurrent action spectra clearly reveal that TCO‐based DSSCs using (Co(bpy)) electrolyte exhibits photon harvesting (incident photon to current conversion efficiency (IPCE) 52%) in the 370–450 nm wavelength region as compared to photon harvesting at peak absorption of the dye (IPCE 56% at 550 nm), which is almost the same (IPCE 47%) in the 400–610 nm wavelength region for TCO‐less DSSCs. Under similar experimental conditions, replacing indoline dye D‐205 to porphyrin‐based dye YD2‐o‐C8 led to the enhancement in the photoconversion efficiency from 3.33% to 4.84% under simulated solar irradiation. Copyright © 2014 John Wiley & Sons, Ltd.     

Stacked graphene–TiO2 photoanode via electrospray deposition for highly efficient dye-sensitized solar cells

A series of TiO₂–graphene stacked photoanodes for dye-sensitized solar cells (DSSCs) were fabricated by electrospray (E-spray) deposition. Among devices incorporating single graphene layer with different deposition times, device with 1 min graphene deposition gave the best performance. For multi-graphene-layer involved devices, best result was obtained with 3 layers of graphene. The working principles were analyzed by scanning electron microscopy, transmittance spectra, electrochemical impedance spectroscopy and incident-photo-conversion efficiency data. We found that although graphene layers incorporated in TiO₂ photoanode slightly decreased dye adsorption, they were able to significantly improve the electron transport, and the charge recombination at the interfaces of TiO₂/dye and TiO₂/electrolyte were greatly suppressed, leading to dramatic improvement in power conversion efficiency. When inserting three layers of pure graphene into the TiO₂ photoanode, high efficiency of 8.9% was obtained, constituting an over 23.6% improvement. Further increasing graphene layers to five, although electron lifetimes is the longest, both the largest charge transfer resistance and the least amount of the dye loading lead to the lowest device efficiency. Our work demonstrated, that pure graphene layer can be successfully incorporated into TiO₂ photoanode by E-spray method with easiness of thickness control and the photoanode with graphene/TiO₂ alternatively layered structure is an excellent candidate for DSSCs.     

Dependence of energy conversion efficiency of dye-sensitized solar cells on the annealing temperature of TiO2 nanoparticles

Dye-sensitized solar cells (DSSCs) were fabricated from porous electrodes derived from sol–gel-synthesized (SGS) nanoparticles (NPs) of TiO₂. Current–voltage measurements were performed to investigate performance characteristics of electrodes derived from SGS-NPs of TiO₂ annealed at different temperatures. Experimental results indicate that the effects of bulk traps and surface states within TiO₂ films on recombination of photo-injected electrons in DSSCs depend upon annealing temperature of SGS-TiO₂ NPs. Moreover, electrodes fabricated from SGS-TiO₂ showed higher photoelectric conversion efficiency than nonporous commercial (P25) TiO₂ NPs. Porous structures within SGS-TiO₂ NPs are of great benefit to sensitizer dye adsorption, and consequently to improvement of photo-electrochemical properties of DSSCs.     

Ag/TiO2/WO3 nanoparticles with efficient visible light photocatalytic activity

A simple strategy for synthesizing Ag decorated TiO2/WO3 composite nanoparticles by sol-gel method used as recyclable photocatalyst is introduced. The photocatalytic efficiency to the degradation of methyl blue (MB) by Ag/TiO2/WO3 nanoparticles is studied under ultraviolet-visible (UV-Vis) light irradiation. It shows that the photocatalytic efficiency of Ag/TiO2/WO3 photocatalyst achieves 96% in 20 min, which is 16 times higher than that of pristine TiO2 at the same conditions. The Ag/TiO2/WO3 photocatalyst can still reach the degradation rate of 90% in the fifth degradation experiment, indicating a good stability and photocatalytic activity.     

Preparation of TiO2 paste starting from organic colloidal suspension for semi-transparent DSSC photo-anode application

We investigated the effect of different formulation strategies on the preparation of TiO2 screen printable pastes starting from the same organic colloidal suspension for dye-sensitized solar cells (DSSCs) application. As first strategy, we developed TiO2 pastes starting from nano-crystalline powder dried from the synthetized suspension, with and without an additional acid treatment, obtaining non-transparent scattering sintered layers. Instead, we demonstrate that starting from the sol solution is a key factor to obtain a well nano-dispersed TiO2 paste. The novel paste process resulted in a final homogeneous and semitransparent porous layer (T>80% @450–550 nm). In order to evaluate the properties of TiO2 powders and inks we performed thermal analysis, BET and FTIR measurements. The films were screen printed on FTO (fluorinedoped tin oxide) glass and characterized after sintering via profilometry, FE-SEM analysis and UVVis spectra measurements. The photo-anode was further validated in small (2 cm2) and large (90 cm2) active area DSSCs, giving an average photovoltaic efficiency respectively of 5,22% and 2,39%, comparable with commercially available TiO2 paste with similar composition.     

Optoelectronic devices informatics: optimizing DSSC performance using random-forest machine learning algorithm

This paper provides an attempt to utilize machine learning algorithm, explicitly random-forest algorithm, to optimize the performance of dye sensitized solar cells (DSSCs) in terms of conversion efficiency. The optimization is implemented with respect to both the mesoporous TiO2 active layer thickness and porosity. Herein, the porosity impact is reflected to the model as a variation in the effective refractive index and dye absorption. Database set has been established using our data in the literature as well as numerical data extracted from our numerical model. The random-forest model is used for model regression, prediction, and optimization, reaching 99.87% accuracy. Perfect agreement with experimental data was observed, with 4.17% conversion efficiency.     

InGaP/GaAs HBT器件的制备及其特性

采用在发射区台面腐蚀时保留InGaP钝化层和去除InGaP钝化层的方法制备了两种InGaP/GaAs异质结双极晶体管(HBT)器件,研究了InGaP钝化层对HBT器件基区表面电流复合以及器件直流和射频微波特性的影响.对制备的两种器件进行了对比测试后得到:保留InGaP钝化层的HBT器件最大直流增益(β)为130,最高振荡频率(fmax)大于53 GHz,功率附加效率达到61％,线性功率增益为23 dB;而去除InGaP钝化层的器件最大β为50,fnax大于43 GHz,功率附加效率为57％,线性功率增益为18 dB.测试结果表明,InGaP钝化层作为一种耗尽型的钝化层能有效抑制基区表面电流的复合,提高器件直流增益,改善器件的射频微波特性.     

不同钝化结构的HgCdTe光伏探测器暗电流机制

在同一HgCdTe晶片上制备了单层ZnS钝化和双层（CdTe+ZnS）钝化的两种光伏探测器,对器件的性能进行了测试,发现双层钝化的器件具有较好的性能．通过理论计算,分析了器件的暗电流机制,发现单层钝化具有较高的表面隧道电流．通过高分辨X射线衍射中的倒易点阵技术研究了单双层钝化对HgCdTe外延层晶格完整性的影响,发现单层ZnS钝化的HgCdTe外延层产生了大量缺陷,而这些缺陷正是单层钝化器件具有较高表面隧道电流的原因．     

Surface nanocrystalline Si structure and its surface passivation for highly efficient black Si solar cells

19.5% conversion efficiency crystalline silicon (Si) solar cells having simple structure without antireflection coating have been fabricated using the surface structure chemical transfer method which produces a nanocrystalline Si layer simply by contacting catalytic platinum with Si wafers in hydrogen peroxide plus hydrofluoric acid solutions. The reflectivity becomes less than 3% after the surface structure chemical transfer method due to formation of black Si. Deposition of phosphosilicate glass and heat treatment at 925 °C performed for formation of pn‐junction effectively passivate the nanocrystalline Si surface. With this phosphosilicate glass passivation plus the hydrogen treatment at 400 °C, the internal quantum efficiency is greatly improved and reaches 81% at a wavelength of 400 nm. Analysis of ellipsometry data shows that incident light with wavelength shorter than 400 nm is almost completely absorbed by the nanocrystalline Si layer. The high internal quantum efficiency for short wavelength light is attributed to effective surface passivation and the nanocrystalline Si layer band‐gap energy which decreases with the distance from the top of the network structure of the nanocrystalline Si layer. Copyright © 2017 John Wiley & Sons, Ltd.     

Solution-based nanostructure to reduce waveguide and surface plasmon losses in organic light-emitting diodes

Organic light-emitting diodes (OLEDs) typically have low out-coupling efficiency. In this paper, a solution-based nanoparticle layer is presented as a nanostructure to enhance the out-coupling efficiency of OLEDs. Silica nanoparticles (NPs) are randomly distributed on indium tin oxide by spin-coating a silica NP solution. By further spin-coating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as a hole injection layer, a randomly corrugated PEDOT:PSS layer is fabricated. A nanostructured OLED having the corrugated PEDOT:PSS layer above the NP layer shows enhanced external quantum efficiency and power efficiency because the trapped light of the waveguide and surface plasmon modes is extracted by Bragg diffraction. The nanostructured OLED shows no angular dependence due to the broad periodicities of the corrugation. The simply fabricated and cost-effective silica NP layer nanostructure, which does not require a lithography step, has potential to enhance the efficiency of both white OLED displays and lighting.     

SiO_2钝化层对GaN基PIN结构核探测器漏电流的影响

成功地制备了有SiO2钝化层和无SiO2钝化层的GaN基PIN结构核辐射探测器,并对二者的I-V特性进行了测试。实验结果表明,SiO2钝化层的存在显著地降低了GaN基PIN结构核辐射探测器的反向漏电流,在-40V的反向偏压情况下,漏电流约有2个数量级的降低。实验过程中观测到随着反向偏压的增大,SiO2钝化层对器件反向漏电流的抑制效应更明显。建立了一种表面沟道模型解释了SiO2钝化层对漏电流的影响。     

Surface property of passivation layer on integrated circuit chip and solder mask layer on printed circuit board

Adhesion of underfill to passivation layer on integrated circuit chip and solder mask layer on printed circuit board is critical to the reliability of an underfilled flip chip package. In this study, the surface properties of solder mask and four passivation materials: benzocyclobutene (BCB), polyimide (PI), silicon dioxide (SiO/sub 2/), and silicon nitride (SiN) were investigated. A combination of both wet and dry cleaning processes was very effective to remove contaminants from the surface. The element oxygen, introduced during O/sub 2/ plasma treatment or UV/O/sub 3/ treatment, led to the increase of the base component of surface tension. X-ray photoelectron spectroscopy (XPS) experiments confirmed the increase of oxygen concentration at the surface after UV/O/sub 3/ treatment. Wetting of underfill on passivation and solder mask was slightly improved at higher temperatures. Although UV/O/sub 3/ cleaning and O/sub 2/ plasma treatment significantly improved the wetting of underfill on passivation materials, they did not improve adhesion strength of epoxy underfill to passivation. Therefore, the wetting was not the controlling factor in adhesion of the system studied.