CdS量子点敏化ZnO薄膜的制备及其性能研究

本文以Zn(CH3COO)2·2H2O、CdCl2和硫脲的水溶液分别为前驱体,采用超声喷雾热解法在ITO导电玻璃上成功的制备了CdS量子点敏化ZnO薄膜(ZnO∶ CdS).通过扫描电镜(SEM),X射线衍射(XRD),光致发光(PL)谱和吸收光谱对CdS量子点敏化ZnO薄膜形貌,结构和光学性能进行了研究.SEM图表明CdS量子点已成功沉积到ZnO薄膜上,量子点呈颗粒状,直径约71 nm.XRD结果显示,除观察到原有的ZnO特征峰外,在2θ=30.3°处有一明显的特征峰,对应着CdS的(111)晶面.PL谱图表明在325 nm的光激发下,CdS量子点敏化ZnO薄膜在400 nm处有一较强的紫外发射峰,在500～700 nm处有一个较宽的黄绿发射带.吸收光谱表明,CdS量子点敏化后ZnO薄膜在可见光区的吸收边为586 nm.     

长寿命水溶性CdS/ZnS核-壳量子点的合成及表征

以一锅法合成的CdS量子点为核心,采用单源分子前驱体法成功制备了高质量的油溶性CdS/ZnS核-壳量子点,量子点荧光量子产率高达43.7;,荧光寿命为306 ns.进一步用谷胱甘肽作为相转移剂,将油溶性CdS/ZnS量子点成功转入水相.采用紫外-可见吸收光谱(UV-vis)、荧光光谱(PL)、时间分辨荧光光谱(TRF)、透射电镜(TEM)和X-射线粉末衍射(XRD)对量子点的光谱性质和形貌、结构进行表征.结果表明:谷胱甘肽修饰的量子点水溶性好,粒径均匀,分散性良好,荧光量子产率高,荧光寿命长,显示了较好的生物分析应用前景.     

CdS沉积次数对TiO2反Opal膜电极光电性能的影响

本文以单分散聚苯乙烯(Polystyrene,简写为PS)微球为模板颗粒,采用室温漂浮自组装法组装了PS opal模板,然后用液相沉积技术填充、去除模板制备了TiO2反opal膜,最后采用化学浴沉积法(Chemistry Bath Deposition,简写为CBD)在TiO2反opal膜上沉积CdS量子点。以CdS量子点敏化的TiO2反opal膜为光阳极组装太阳能电池并测试其光电性能。实验结果表明:CBD沉积CdS量子点次数对TiO2反opal膜电极的光电性能有影响。在本文实验条件下,当CBD沉积次数为5次时,CdS量子点敏化的TiO2反opal膜电极的太阳能电池具有最高光电转化效率。     

化学浴法制备CdS薄膜及其光电性能研究

本文用氯化镉、氯化铵、硫脲和氨水的溶液体系采用化学浴沉积法合成CdS薄膜,制备出均匀、致密的CdS薄膜,通过XRD、SEM、EDS、紫外可见吸收光谱等表征手段研究了CdS薄膜的晶体结构,表面形貌,元素比例和光电性能.发现在不同水浴温度下都成功制备了CdS薄膜,其中75℃制备的CdS薄膜最为均匀致密且其XRD衍射峰强度最强,光吸收边在500 nm附近,禁带宽度大约为2.52 eV.这些CdS薄膜的光电响应大,暗态及光照下的电导率分别为1×10-4S·cm-1和1.04×10-2 S · cm-1.用它们制备的CdS/CZTS异质结太阳电池具有明显的光伏效应.     

氨水浓度对化学水浴法制备CdS缓冲层及CZTSe电池性能的影响

主要研究了化学水浴法沉积CdS薄膜中氨水浓度对薄膜材料特性的影响.通过X射线衍射(XRD)、扫描电子显微镜(SEM)和分光光度计(UV-Vis)等测试手段对制备的CdS薄膜的结构和光学特性进行了分析.结果表明:不同的氨水浓度条件下均得到立方相CdS薄膜,薄膜沿(111)面择优取向生长.随着氨水浓度增加时CdS薄膜表面逐渐变得致密光滑,CdS薄膜的透过率增强和带隙变宽.在氨水浓度为0.10 mol/L时制备出材料特性最佳的CdS薄膜,其表面紧凑致密无针孔,颗粒大小均匀,将其应用于CZTSe薄膜太阳电池中的缓冲层材料,得到光电转化效率为3.12;的CZTSe薄膜太阳电池(该电池未经任何后硒化处理工艺).     

葡萄糖胺稳定CdS量子点的绿色合成及光谱特性

以葡萄糖胺(Glucosamine,GIcN)为稳定剂,以Cd(Ac)2 ·2H2O和Na2S ·9H2O作为反应剂,在室温下水相合成了CdS量子点.通过X射线衍射(XRD)、透射电镜(TEM)、紫外-可见吸收光谱(UV -Vis)和荧光发射光谱(PL)对样品的结构、形貌和光学性能进行了表征,考察了反应体系的pH值、GlcN/Cd的物质的量比对量子点光谱性能的影响.结果表明,所获得的CdS量子点为立方闪锌矿结构,且尺寸分布均一,结晶度高,具有丰富的表面缺陷和量子尺寸限域效应.同时,对CdS量子点形成的可能机理进行了初步的探讨.     

Au／CdS-核／壳结构纳米复合颗粒的制备与表征

本文制备并表征了Au/CdS几何结构的纳米簇复合物.TEM和尺寸分布图显示,Au颗粒和CdS颗粒的平均粒径分别为6 nm和8 nm,Au/CdS粒径分布较窄且分散性较好,平均粒径19 nm.这种核壳结构纳米复合颗粒和单CdS颗粒一样,在485 nm和543 nm有两处发射峰.从UV-Vis上观察到,CdS的吸收边在470 nm,Au/CdS的吸收谱线上Au的吸收峰消失,吸收边相对于单CdS出现蓝移.     

化学水浴沉积法制备硫化镉薄膜的微结构和性能

采用化学水浴沉积法在不同氨水用量下制备了Cu(In,Ga)Se₂太阳能电池的缓冲层CdS薄膜,根据化学平衡动力学计算出混合溶液中反应粒子的初始浓度、pH值和离子积,利用台阶仪、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、量子效率测试仪(EQE)和IV测试仪对制备样品的薄膜厚度、表面形貌、晶体结构、量子效率和光电转换效率进行了表征和分析。结果表明:提高氨水用量可以抑制同质反应,促进异质反应,使CdS薄膜晶体结构从立方相向六方相转变,晶粒形状从柳絮状向颗粒状转变,晶粒尺寸逐渐增大,粒径分布更加均匀,薄膜表面更加平整,制备电池的EQE、V_oc、J_sc、FF、R_s等电学参数得到优化,光电转换效率从7.64%提高到13.60%。     

CdS纳米线分级结构薄膜的制备及光催化性能

采用电沉积-溶剂热两步法制备了Cu基CdS纳米线分级结构薄膜.用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱分析仪(EDS)、紫外-可见漫反射光谱(UV-vis-DRS)等对薄膜进行表征,探讨了Cd基CdS纳米线的成核生长机制.结果显示:Cu基Cd微米片阵列与其表面生长的针状CdS纳米线,构筑形成了多孔道的分级结构薄膜,改变溶剂热的时间、温度及硫源浓度,CdS纳米线尺寸呈规律性变化.Cu基CdS薄膜具有较好的光催化活性和稳定性,经5次光催化循环,罗丹明B(RhB)降解率下降不明显.     

CdS薄膜中"白斑"的研究

本论文对CdS薄膜中的"白斑"进行了研究.化学水浴沉积法(CBD)制备CdS薄膜所需要的化学反应物包括硫脲、氨水、镉盐和铵盐等.文中采用两种镉盐和铵盐来沉积CdS薄膜:氯化镉和氯化铵,乙酸镉和乙酸铵.所沉积的CdS薄膜的表观形貌由SEM表征,成分由EDX表征.当镉盐和铵盐分别采用氯化镉和氯化铵时,生成的薄膜中存在大量的"白斑".这些"白斑"的成分不是CdS,而是(CdCl)2S.增加氨水的浓度可以大大减少这些"白斑",但是不能彻底消除这些"白斑".当镉盐和铵盐分别采用乙酸镉和乙酸铵时,生成的薄膜均匀、平整,薄膜中根本就不存在所谓的"白斑".因此,沉积CdS薄膜时,镉盐和铵盐不宜采用氯化镉和氯化铵,应该采用乙酸镉和乙酸铵.     

Preparation of dendritic‐like CdS by hydrothermal method and its photocatalytic performance

In this article, dendritic‐like CdS has been prepared by a hydrothermal method using thiourea as the sulfur source, and the effects of experimental conditions on the morphologies of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and the fluorescence and photodegradation properties of CdS have also been investigated. The XRD result indicates that the dendritic‐like CdS are of hexagonal phase and they are highly crystallized. Also, the FESEM results show that the ratio of raw material affects the yield of CdS, the reaction time affects the morphology of CdS. The best morphology of CdS is dendritic structures and the length is about 6 μm. The fluorescence spectrum shows three peaks at 470 nm, 513 nm and 547 nm, which indicates that the dendritic‐like CdS mainly emits green and blue fluorescence. Moreover, the dendritic‐like CdS exhibits good photocatalytic activity and its photodegradation rate to methylene blue can reach 92%. The growth mechanism for the formation of CdS with dendritic structure is also described.     

Optical properties of flower‐like CdS prepared by a hydrothermal method with SDBS as surfactant

In this article, flower‐like CdS structures have been prepared by a hydrothermal method with SDBS as surfactant. The influences of different experimental conditions on the morphologies, UV‐Vis and fluorescence properties of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV–Vis) and room‐temperature photoluminescence (PL). The XRD result indicates that the flower‐like CdS structures are of hexagonal phase. The FESEM results indicate that the main role of SDBS is to make the CdS crystals assemble together to form the flower‐like structures. The UV–Vis results show CdS has a strong absorption in the ultraviolet region and visible‐light region. The PL results show CdS has two emission peaks, respectively at 461 nm and 553 nm. The growth mechanism for the formation of flower‐like CdS structures is also described.     

One‐step green synthesis by organic molten salt method and optical properties of CdS nanosheets

Cadmium sulfide (CdS) nanosheets were synthesized by an environment friendly, “green” organic molten salt (OMS) method at 220 °C. The as‐synthesized products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), respectively. The XRD results reveal that the as‐synthesized CdS nanosheets are of the hexagonal wurtzite structure and the CdS nanosheets grow along the c‐axis. The SEM results indicate that the diameters and thickness of the CdS nanosheets are about 20–40 nm and 5–10 nm, respectively. The optical properties of the CdS nanosheets were investigated by ultraviolet–visible (UV‐Vis) spectroscopy and photoluminescence (PL) spectroscopy. The ultraviolet–visible spectrum exhibits two excitonic peaks with a step‐like absorption and the photoluminescence spectrum shows a green emission peak centered at around 524 nm. A possible growth mechanism of CdS nanosheets was discussed.     

空位浓度对纤锌矿CdS电子结构和光学性质影响的第一性原理研究

本文基于密度泛函理论的平面波超软赝势方法,采用第一性原理研究了含Cd空位缺陷CdS和含S空位缺陷纤锌矿CdS的几何结构、能带结构、电子态密度及光学性质。通过计算分析可知,含Cd空位缺陷的CdS体系均为p型半导体,含S空位缺陷的CdS体系跃迁方式均由直接跃迁变为间接跃迁。Cd、S空位缺陷的CdS体系的态密度总能量降低。空位CdS体系相较于本征CdS体系的静介电常数均有提高,并随着空位浓度的增大而增大,Cd空位缺陷体系更为明显,极化能力得到显著提升。空位Cd的CdS体系相较于本征CdS体系在红外波段存在明显的吸收,空位S的CdS体系相较于本征CdS体系在可见光波段存在明显的吸收。     

Rotary target method to prepare thin films of CdS/SiO2 by pulsed laser deposition

Thin films of CdS-doped SiO₂ glass were prepared by using the conventional pulsed laser deposition (PLD) technique. The laser target consisted of a specially constructed rotary wheel which provided easy control of the exposure-area ratio to expose alternately the two materials to the laser beam. The physical target assembly avoided the potential complications inherent in chemically mixed targets such as in the sol–gel method. Time-of-flight (TOF) spectra confirmed the existence of the SiO₂ and CdS components in the thin-film samples so produced. X-ray diffraction (XRD) and atomic force microscopy(AFM) results showed the different sizes and structures of the as-deposited and annealed films. The wurtzite phase of CdS was found in the 600^oC-annealed sample, while the as-deposited film showed a cubic–hexagonal mixed structure. In the corresponding PL (photoluminescence) spectra, a red shift of the CdS band edge emission was found, which may be a result of the interaction between the CdS nanocrystallite and SiO₂ at their interface.     

熔盐法制备三元层状MAX相陶瓷的研究进展

MAX相是一种兼具金属和陶瓷性能的新型三元层状过渡金属碳氮化物。传统合成MAX相的方法都有一定的局限性,如反应温度较高、合成时间过长、合成样品较少,且大部分无法直接一步制备所需MAX相。近些年来,采用熔盐法合成MAX相的报道越来越多,并且工艺持续改进。本文从传统熔盐法合成MAX相出发,分析并阐述了新熔盐法合成MAX相的研究进展。传统熔盐法利用较低熔点的熔盐作为反应溶剂,提高了反应效率;熔盐屏蔽法以熔盐作为反应溶剂的同时还可防止氧化,使得反应可以在空气中进行;路易斯酸盐法则是将熔盐作为反应原料来合成MAX新相;熔盐电化学法以电脱氧的方式,将合成原料由纯金属改为金属氧化物,降低了生产成本。熔盐法所合成MAX相产物较传统方法所合成产物的产量及纯度更高,所需要的温度、能耗以及成本更低。因此,熔盐合成法是未来大批量合成MAX相以及MAX新相合成的一个重要方法。     

水热法制备ZnO晶体及纳米材料研究进展

纳米ZnO材料是新型宽禁带半导体材料,具有优良的光学及电学性能,在太阳能电池电极及窗口材料、声表面波材料、光电材料、敏感材料等方面得到广泛应用.纳米ZnO材料性能与制备技术有很大关系,本文综合评述了水热法制备纳米ZnO材料研究现状,研究了其制备特点及制备机理,从纳米ZnO晶体、阵列或薄膜、粉体三个方面制备实例研究了水热制备方法,最后探讨了纳米ZnO材料发展前景.     

CdS纳米棒的水热法制备及形成机理研究

采用水热法以Na2S· 9H2O为硫源,Cd3O12S3·8H2O为镉源,PVP为表面活性剂,成功制备了CdS纳米棒.并利用X射线衍射(XRD)、透射电子显微镜(TEM)和相应选区电子衍射(SAED)、高分辨透射电子显微镜(HRTEM)、X射线能量色散分析谱仪(XEDS)和紫外可见(UV-vis)分光光度计等测试手段对样品的晶体结构、形貌、微观结构和光学特性等特征进行了表征分析,实验结果表明本方法所制备的CdS纳米棒为纤锌矿结构,沿[001]方向择优生长,平均直径大约为50 nm,棒宽均匀、分散性好,带隙为2.43 eV.同时也对CdS纳米棒的形成机理进行了初步探讨,提出了CdS纳米棒的生长模型,其形貌从三角形到阶梯形棒晶,最后再到完整的棒状晶体的一个定向团聚的自组装过程.     

Novel route to scalable synthesis of II–VI semiconductor nanowires: Catalyst-assisted vacuum thermal evaporation

Vacuum thermal evaporation, a conventional film fabricating technique, has been explored to synthesize II–VI semiconductor nanowires based on a catalyst-assisted vapor–liquid–solid (VLS) process. Low melting-point metals, such as bismuth and tin, can be used as catalysts by co-evaporating with desired semiconductor materials. As proof of the concept, CdTe, CdS, ZnSe and ZnS single crystalline nanowires have been successfully synthesized on a large scale by this method. The growth mechanism involved in the method has been discussed. Morphological, structural and optical properties of as-synthesized nanowires were characterized, revealing the high quality of the nanowires. The results indicate that the method presented here is a novel and general route to mass production of II–VI semiconductor nanowires, which can be possibly scaled up for industrial application at low cost, and extended to other material systems.