A new technique for large-area thin film CdS/CdTe solar cells

The atmospheric pressure CSS method has been developed as a reproducible and efficient process. Thin film CdTe grown under atmospheric pressure has a rough surface morphology. The density of carbon black powder in the graphite carbon paste for screen printing is a key factor in reducing the series resistance of the device with rough surface CdTe. Using graphite carbon paste with 7 wt% carbon black powder has resulted in cells with a relatively low back contact resistance. A highly efficient large-area CdS/CdTe solar cell (11.0%, 5327 cm²) sub-module has been fabricated using the new technique.     

Enhancement of the photoelectrochemical response of poly(terthiophenes) by CdS(ZnS) core-shell nanoparticles

We have investigated the photoelectrochemical properties of hybrid films of polythiophenes poly(4,4″dimethoxy-3′-methyl-2,2′:5′,2″ terthiophene) (PDM), poly(4,4″dipentoxy-3′-methyl-2,2′:5′,2″ terthiophene) (PDP), and cadmium sulfide/zinc sulfide (CdS(ZnS)) core-shell nanoparticles. Although CdS(ZnS) nanoparticles present enhanced exciton trapping, light harvesting by hybrid films was enhanced when compared to those of pure PDM and PDP films. This enhancement is explained in terms of electron and hole transfer mechanisms at different excitation wavelengths. The more efficient light harvesting of PDM/CdS(ZnS) when compared to that of PDP/CdS(ZnS) was attributed to its broader absorption spectrum and more efficient electron hopping.     

Doping behavior of iodine in Hg0.8Cd0.2Te+

Iodine doped single crystal samples of Hg_0.8Cd_0.2Te were annealed at temperatures varying from 450 to 600°C in Hg vapor and quenched to room temperature. Hall effect measurements at 77 K on the crystals cooled to room temperature indicate the samples to be n-type after anneals at high Hg pressures whereas they turn p-type after anneals at low Hg pressures; the electron concentration increases with increase in Hg pressure. The results are explained on the basis that the crystals are saturated with (Hg,Cd)I₂, with the iodine being present as donors occupying tellurium lattice sites (I_Te) and a fraction being present as (I_TeV_Hg)’ species formed from the iodine on tellurium lattice sites (I_Te) pairing with the doubly ionized native acceptor defects (V^Hg/11). The solubility of the I_Te species increases with increase in Hg pressure, whereas that of the (I_TeV_Hg)’ species increases with decrease in Hg This work was supported by NASA under contract NAS8-33245 pressure. Equilibrium constants for the incorporation of the iodine species as well as the pairing reaction have been established     

Effect of formate and methanol on photoreduction/removal of toxic cadmium ions using TiO2 semiconductor as photocatalyst

Photoreduction/removal of cadmium was studied at pH 7 using TiO₂ Degussa as photocatalyst, and either formate or methanol as hole scavengers. In the absence of organic additives, approximately 60% of cadmium was found to be removed from the solution by adsorption. Addition of formate resulted in the photoreduction of cadmium to its metallic form. No cadmium reduction was observed when methanol was added as the hole scavenger. Zeta potential measurements of the catalyst suspensions and studies on the extent of organic additive adsorption and mineralisation were used to prove the photoreduction process. It was found that the adsorption of both cadmium and the organic hole scavenger is crucial for the photoreduction of cadmium. It is postulated that to be an effective hole scavenger the organic additive needs to be easily photooxidised under an anoxic environment. In addition, the presence of formate radicals could be responsible for the Cd photoreduction.     

根际微生物促进下鱼腥草对镉的富集作用

初次探讨了鱼腥草在根际微生物的促进下对土壤镉的富集作用。研究表明当土壤中镉(Cadmium)含量在5mg•kg-1时,鱼腥草(Houttuynia cordata , HCT)对镉的富集率为2.86％,镉含量为10 mg•kg-1时富集率1.63％,鱼腥草对镉的吸收量最高可以达到培养前自身镉浓度的200倍（培养前鱼腥草镉含量0.1146 mg•kg-1,培养后最高达24.44 mg•kg-1）,说明鱼腥草对镉有很强的富集作用。研究中还发现,细菌、霉菌对镉的耐性很弱,而培养初期放线菌对镉的耐性很强,较高浓度镉可能刺激了放线菌的大量生长。并且在鱼腥草根系和微生物的联合作用下,土壤微生态系统能够保持较好的稳定性。因此植物-微生物联合修复重金属污染土壤技术,可以实现土壤的生态修复,拥有很大的应用前景。     

活性炭纤维对水中镉离子的吸附研究

以活性炭纤维作为去除水中镉离子的吸附剂。考察了振荡时间、活性炭纤维用量、水样pH对吸附效果的影响。并通过等温吸附平衡实验作出了吸附等温线 ,采用有关的等温吸附模式对吸附平衡实验数据作了线性模拟 ,对吸附规律进行了探讨。结果表明 ,振荡时间、活性炭纤维用量、pH是影响镉离子在活性炭纤维上吸附效果的主要因素 ,吸附效率随着振荡时间的延长、活性炭纤维用量的增加、pH的增大而增大。吸附容量随活性炭纤维用量的增加而减小。镉离子在活性炭纤维上的吸附规律可用Langmuir模式和Freundlich模式很好地描述。吸附形式呈单分子层且容易进行。结果表明 ,活性炭纤维对水中镉离子的吸附特性良好 ,可作为去除水中离子态镉的优良吸附剂。     

一步法合成硫脲的研究

采用含氮量≥20％的石灰氮(CaCN2)水解物和H2S直接反应，一步法生成硫脲．该反应分两个阶段完成：反应的第一阶段为HzS的吸收过程，受其溶解度的影响，常压下有利反应的温度为35C左右，反应液中除了溶解的H2S和未水解的CaCN2外，主要有Ca(SH)2和H2CN2以及少量副反应生成的尿素；第二阶段主要是Ca(SH)2和H2CN2继续反应，生成CS(NH2)2(硫脲)，反应主要受硫脲生成速度的影响，温度宜控制在80～85℃，时间不得超过5h．该法所得硫脲按ZBG17013-88分析为合格产品．     

铁氧体法处理含铬和镉废水的研究

用铁氧法处理含铬和镉废,在pH值为12、温度为70℃、滴加适量双氧水时,即可得磁性较强的铁氧体,同时,被处理后的废水中铬和镉的含量分别降低至0．008mg/L和0．041mg/L,均达到排放标准。     

镉离子对铅阳极电化学行为的影响

应用循环伏安方法研究了铅电极在不同镉离子浓度含量的硫酸溶液中的阳极氧化行为 ,采用SEM、XRD方法观测了铅阳极阳极氧化形成的硫酸铅晶粒大小及二氧化铅的结晶结构。结果表明 :溶液中的镉离子对铅转化为硫酸铅有较大影响 ,对二氧化铅的结晶结构及形貌无明显作用