Comprehensive study of efficient dye-sensitized solar cells based on the binary ionic liquid electrolyte by modifying with additives and iodine

The photovoltaic performance of dye-sensitized solar cells (DSSCs) is enhanced by modifying the binary room temperature ionic liquid (RTIL) electrolyte with additives and iodine. The average photoelectric conversion efficiency (PCE) of 6.39% is achieved. Through electrochemical impedance spectroscopy (EIS), cyclic voltammetry scans and incident photon-to-current conversion efficiency (IPCE) data, the working principles are analyzed. The enhancement is mainly attributed to the improvement of short circuit current which is caused by the reduction of overall internal resistance of the devices. Durability tests are measured at room temperature, and the long-term stability performance can be maintained. This work has been supported by the National Natural Science Foundation of China (No.61474064). E-mail:zcliang@njupt.edu.cn      

Effect of deoxycholic acid on performance of dye-sensitized solar cell based on black dye

The effect of coadsorption with deoxycholic acid (DCA) on the performance of dye-sensitized solar cell (DSSC) based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3](tcterpy= 4,4′,4"-tricarboxy-2,2′:6′,2"-terpyridine), a socalled black dye, had been investigated. Results showed that the coadsorption of DCA with the black dye results in significant improvement in the photocurrent and mild increase in the photovoltage, which leads to an enhancement of overall power conversion efficiency by 9%. The enhancement of photocurrent was attributed to the increased efficiency of charge collection and/or electron injection. The coadsorption with DCA suppressed charge recombination and thus improved open-circuit photovoltage.     

High performance room temperature nematic liquid crystals based on laterally fluorinated isothiocyanato-tolanes

High birefringence and low viscosity isothiocyanates liquid crystal single compounds and eutectic mixtures, based solely on laterally fluorinated aromatic rigid core structures, are reported. Extraordinarily high values of figure-of-merit were observed at room temperature and also elevated temperatures for the nematic mixtures we formulated. Potential applications of such mixtures for laser beam steering at /spl lambda/=1.55 /spl mu/m using optical phased arrays are emphasized.     

溶剂对离子液体电化学电容器电解液的影响

研究了有机溶剂[乙腈(AN)、丙酮(Acet)]对离子液体1-乙基-3-甲基咪唑四氟硼酸盐[(EMIm)BF4]电导率和电化学性能的影响。混合电解液体系的电导率在离子液体与有机溶剂的摩尔比为4∶6时达最大值。循环伏安和恒流充放电测试结果表明,添加有机溶剂在很大程度上改善了电容器的电容特性。电容器的比电容在(EMIm)BF4与AN或Acet的摩尔比为4∶6时达最大值,分别为233,173F/g。     

Enhanced performance of dye-sensitized solar cells with novel 2,6-diphenyl-4H-pyranylidene dyes

Novel 2,6-diphenyl-4H-pyranylidene derivatives were designed and synthesized as dyes for dye-sensitized solar cells (DSSC). Dyes 2a, b with a phenyl substituent showed high DSSC energy conversion efficiencies of 5.3% (J_sc = 10.3 mA/cm², V_oc = 0.72 V, FF = 0.72) and 4.7% (J_sc = 8.9 mA/cm², V_oc = 0.73 V, FF = 0.72) at 100 mW/cm² under simulated AM 1.5 G solar light conditions. These values are twice better than that of dye 1 without the phenyl substituent under the same conditions. Both the photocurrent density (J_sc) and open circuit voltage (V_oc) of DSSCs based on dyes 2a, b are increased compared with 1. It can be attributed to their twisted structures, absorption abilities and proper energy levels. This result shows that the tetraphenylpyranylidene is a promising electron-donor unit for high-efficiency DSSCs.     

Efficient gel-state dye-sensitized solar cells adopting polymer gel electrolyte based on poly(methyl methacrylate)

We report an effective method to fabricate gel-state dye-sensitized solar cells (DSSCs) based on the PMMA polymer gel electrolyte. In this approach, the liquid-state polymer electrolyte solution was prepared by simply mixing the traditional liquid-state electrolyte with the polymer gelator solution and was injected into the DSSC in its liquid state. The liquid-state polymer electrolyte was then converted to the gel state (i.e., in situ gelation) simply by evaporating a portion of solvents at elevated temperatures. With this approach, liquid electrolytes already well developed and optimized for DSSCs can be readily adopted. Filling in the liquid/solution state ensures effective penetration of the electrolyte into pores of TiO₂ nanoparticle electrodes for attaining good contact and interface properties. The in situ gelation by heating (solvent evaporation) much simplifies the process. The polymer gel electrolyte thus prepared exhibited high ion conductivity and diffusivity comparable to those of traditional liquid electrolytes. The gel-state DSSCs thus fabricated exhibited a high power-conversion efficiency of 8.03% and much improved stability compared to the traditional liquid DSSC.     

TiO2基染料敏化太阳能电池的表面修饰及性能研究

采用水热法制备TiO₂浆料,用La(NO₃)₃溶 液浸泡TiO₂薄膜获得修饰电极。用X射线光电子能谱(XPS) 和扫描电子显微镜(SEM)对修饰电极的主要成分及形貌进行表征的结果显示,电极薄膜分为 上下两层,表 面包覆层粒径较大,为La₂O₃颗粒;下层颗粒粒径较小,为TiO₂颗粒。电流-电压测 试结果显示,与修饰 前相比,用La(NO₃)₃溶液浸泡30min获得的膜电极性能最优,使 开路电压和短路电流分别提高了6.8%和 18.5%。电化学阻抗谱(EIS)测试结果表明,相同偏压下,TiO₂/La ₂O₃电极界面复合电阻比TiO₂要大,说明 La₂O₃包覆层在一定程度上抑制了界面的电子复合,改善了电池的光电化学性能。     

TiO2纳米管阵列对染料敏化太阳能电池性能的影响

通过恒压阳极氧化法在Ti箔表面制备了结构规整的TiO2纳米管阵列,研究了氧化时间和退火温度对纳米管阵列的尺寸和晶体结构的影响。用制得的纳米管阵列电极组装了染料敏化太阳能电池(DSSC),研究了纳米管长度、退火温度和电极面积对DSSC光电性能的影响。结果表明,纳米管管径和壁厚均与氧化时间无关,而纳米管长度则随着氧化时间延长而增加。在450℃及更低温度退火时,纳米管中只出现锐钛矿相;而在500℃退火时,纳米管中则又出现了金红石相。由厚度为27μm、退火温度为450℃的纳米管阵列电极组装成的DSCC具有最佳的光电转化性能。DSCC的光电转化效率随电极面积的增加而降低。     

Basic aspects of the temperature coefficients of concentrator solar cell performance parameters

The basis for the temperature dependence of the principal performance parameters of single and multi‐junction concentrator solar cells is examined, focusing on the impact of bandgap and irradiance. The analysis of cells in the radiative limit establishes fundamental bounds. A quasi‐empirical model yields predictions consistent with available data. A simple method for estimating the temperature coefficients of key performance parameters is identified. The degree to which the efficiency penalty associated with cell heating can be mitigated by high irradiance is also evaluated. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of ionic liquid concentration on the electromechanical performance of ionic electroactive polymer actuators

We have investigated influence of ionic liquid concentration on the electromechanical response of ionic electroactive polymer actuators. Actuators were fabricated from ionomeric membrane and doped with different concentrations of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid. Samples were investigated for their electromechanical and electrochemical characteristics; and it was observed that the maximum electromechanical strain of approximately 1.4% is achieved at 22 wt% ionic liquid content. Increasing ionic liquid concentration results in saturation of the electrode–ionomer interface and formation of ionic double/multi layers, which in turn result an inward accumulation of ions; hence, generate strain in an undesired direction that deteriorates the electromechanical response of the actuator.     

硫化钴镍的制备及其作染料敏化太阳能电池对电极的性能研究

不同温度下通过两步水热法在氟掺杂氧化锡导电玻璃上制备了钴镍双金属硫化物对电极。并通过X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、循环伏安测试(CV)、电化学阻抗谱分析(EIS)以及光电流密度-电压特性曲线(J-V)分别研究了其物相、表面化学元素组成及其化学状态、表面形貌、电催化活性和光电转化性能。结果表明该硫化物为直立片状的NiCo_2S_4,90℃制备的对电极具有较高的电催化活性,其电池的光电转化效率达到了与Pt电极电池效率(6.02%)相比拟的值(5.74%)。而120℃制备的对电极虽然具有更大比表面积,但其膜太厚,显著增加了电解质的能斯特扩散电阻,导致其电池效率偏低。     

晶格失配对InAs基室温中波红外探测器性能的影响

采用液相外延技术生长了InAs基室温红外探测器件材料,通过光学显微镜、扫描电子显微镜、X射线衍射仪分析了外延材料表面形貌、截面形貌与晶格失配的关系。分析发现,不恰当的晶体晶格常数匹配度会导致材料表面形貌变差,降低材料的结晶质量,晶格失配在0.22%左右的InAs基外延材料表面形貌较好,缺陷少,晶体质量较好。在此基础上,成功制备出室温探测率D^*为6.8×10⁹ cm·Hz^1/2·W^-1的InAs基室温中波红外探测器,这一性能与国际上红外探测器领军企业美国Teledyne Judson Technologies和日本滨松株式会社的商用InAs基红外探测器性能处于同等水平。     

Enhanced performance of hybrid solar cells based on ordered electrospun ZnO nanofibers modified with CdS on the surface

To improve the performance of the hybrid solar cells based on electrospun zinc oxide nanofibers/poly(3-hexylthiophene) (ZnO/P3HT), we modified the ZnO nanofibers with nanocrystalline cadmium sulfide (CdS) by solution process and successfully obtained CdS/ZnO core–shell nanofibers. The CdS modification at the optimum condition can dramatically improve all photovoltaic parameters and increase the power conversion efficiency of the hybrid solar cells for over 100%. In addition, the lifetimes of carriers in the hybrid solar cells characterized by impedance analyzer become much longer after the modification of CdS. The effect of CdS modification on the devices can be mainly attributed to the cascaded energy band structure of the heterojunction that favors charge transport process and thus increases the efficiencies of the devices.     

染料敏化太阳能电池TiO2薄膜电极的染料吸附性能研究

采用手工刮涂法制备了染料敏化太阳能电池( DSSC)的TiO2薄膜电极,用解吸的方法和正交试验研究了DSSC电池TiO2薄膜电极的染料吸附性能,并结合统计分析方法对染料吸附试验数据进行了分析处理.研究结果表明TiO2薄膜电极具有最优染料吸附性能的烧结条件为:以2℃/min的速率升温至450℃,保温50 min后随炉冷却...     

基于三氯氧磷液态源扩散技术的太阳能电池转换效率研究

通过对太阳能电池片扩散工艺中扩散端POCl3流量的控制实验,研究了POCl3流量对所制太阳能电池的等效串联电阻RS、漏电阻RSH以及转换效率的影响。结果表明:RS和RSH都随POCl3流量减小而增大。当POCl3流量为950 mL/min时,所制太阳能电池转换效率达到最大值16.69%,比常规生产(POCl3流量为1 000 mL/min)的转换效率提高了0.35%。     

Characterization of a room temperature terahertz detector based on a GaN/AlGaN HEMT

We report on the characterization of a room temperature terahertz detector based on a GaN/AlGaN high electron mobility transistor integrated with three patch antennas.Experimental results prove that both horizontal and perpendicular electric fields are induced in the electron channel.A photocurrent is generated when the electron channel is strongly modulated by the gate voltage.Despite the large channel length and gate-source/drain distance, significant horizontal and perpendicular fields are achieved.The device is well described by the self-mixing of terahertz fields in the electron channel.The noise-equivalent power and responsivity are estimated to be 100 nW/（Hz）^1/2 and 3 mA/ W at 292 K,respectively.No decrease in responsivity is observed up to a modulation frequency of 5 kHz. The detector performance can be further improved by engineering the source-gate-drain geometry to enhance the nonlinearity.     

基于GaN/AlGaN高电子迁移率场效应晶体管的室温太赫兹探测器

本文主要论述一种带平板天线,基于GaN/AlGaN高电子迁移率场效应晶体管的室温太赫兹探测器。太赫兹辐射下,由于天线的作用会在栅下感应出平行沟道和垂直沟道的太赫兹电场,由此在源漏产生强烈依赖于栅压的直流光电流。尽管栅极远离源漏两端,平行沟道和垂直沟道的太赫兹电场依然很强。探测器可以用自混频理论很好的描述。在室温下,探测器的响应度和噪声等效功率分别为100 nW/sqrt（Hz）和 3 mA/W。探测器具有很高的响应速度,在5 KHz的调制下,光电流没有衰减。如果缩少栅极和源漏的距离将进一步提高探测灵敏度。     

Novel 4H-pyranylidene organic dyes for dye-sensitized solar cells: Effect of different heteroaromatic rings on the photovoltaic properties

Eight novel Ruthenium-free dyes consisting of a 4H-pyranylidene donor, a 2-cyanoacrylic acid acceptor and several heterocyclic rings with different electronic properties are designed and synthesized. The photovoltaic performances of the related dye-sensitized solar cells are discussed and compared, obtaining the best results with the thiophene followed by the mismatched-oriented thiazole. Dyes containing a pyrrol or a matched-oriented thiazole lead to the lower efficiencies of all the series. Charge extraction (CE) and transient photovoltage (TPV) measurements were conducted in order to investigate the recombination resistance and the difference in voltage for the devices. In order to get further insight in the electronic and optical properties of the studied compounds, theoretical calculations using TD-DFT and the CPCM have been carried out.