核壳结构CdS/ZnS纳米微粒的制备与光学特性

用微乳液法制备CdS纳米微粒 ,以ZnS对其进行表面修饰 ,得到具有核壳结构的CdS/ZnS纳米微粒 .采用X射线衍射 (XRD)、透射电镜 (TEM )表征其结构、粒度和形貌 ,紫外 可见吸收光谱 (UV)、光致发光光谱(PL)表征其光学特性 .制得的CdS近似呈球形 ,直径为 3.3nm ;以XRD和UV证实了CdS/ZnS核壳结构的实现 .研究了不同ZnS壳层厚度对CdS纳米微粒光学性能的影响 ,UV谱表明随着壳层厚度的增加纳米微粒的吸收带边有轻微的红移 ,同时短波吸收增强 ;PL谱表明壳层ZnS的包覆可减少CdS纳米微粒的表面缺陷 ,带边直接复合发光的几率增大 ,具有合适的壳层厚度时发光效率大大提高 .     

n-ZnO:Al/i-ZnO/n-CdS/p-Cu2ZnSnS4太阳能电池光伏特性的分析

具有高光吸收系数的半导体Cu₂ZnSnS₄ (CZTS)薄膜是一种新型太阳能电池材料. 本文对n-ZnO:Al/i-ZnO/n-CdS/p-CZTS结构的CZTS薄膜太阳能电池进行分析, 讨论CZTS薄膜的掺杂浓度、厚度、缺陷态和CdS薄膜的掺杂浓度、 厚度对太阳能电池转换效率的影响以及太阳能电池的温度特性. 分析表明, CZTS薄膜作为太阳能电池的主要光吸收层, CZTS薄膜的掺杂浓度和厚度的取值对太阳能电池的转换效率有显著影响, CZTS薄膜结构缺陷态的存在会导致太阳能电池性能的下降. CdS缓冲层的掺杂浓度、厚度对太阳能电池光伏特性的影响较小. 经结构参数优化得到的n-ZnO:Al/i-ZnO/n-CdS/p-CZTS薄膜太阳能电池的最佳光 伏特性为开路电压1.127 V、短路电流密度27.39 mA/cm²、填充因子87.5%、 转换效率27.02%,转换效率温度系数为-0.14%/K.     

ZnS/CdS复合窗口层对CdTe太阳能电池短波光谱响应的影响

采用磁控溅射法制备了ZnS/CdS复合窗口层,并将其应用于CdTe太阳能电池。对所制备薄膜的形貌和结构等进行了研究。测试了具有不同窗口层的CdTe太阳电池的量子效率和光Ⅰ-Ⅴ特性,分析了ZnS薄膜制备条件对CdTe电池器件性能影响;研究了CdS薄膜厚度和ZnS/CdS复合窗口层对短波区透过率以及CdTe太阳电池的光谱响应的影响。着重研究了具有ZnS/CdS复合窗口层的CdTe太阳电池的短波光谱响应。结果表明,CdS窗口层厚度从100 nm减至50 nm后,其对短波区光子透过率平均提高了18.3%,CdTe太阳电池短波区光谱响应平均提高了27.6%。衬底温度250 ℃条件下制备的ZnS晶粒尺寸小于室温下制备的ZnS。具有ZnS/CdS复合窗口层的CdTe电池中,采用衬底温度250 ℃沉积ZnS薄膜来制备窗口层的电池器件,其性能要优于室温下沉积ZnS制备窗口层的电池器件。这说明晶粒尺寸的大小对电子输运有一定影响。在相同厚度CdS的前提下,具有ZnS/CdS复合窗口层的CdTe电池比具有CdS窗口层在短波的光谱响应提高了约2%。这说明ZnS/CdS复合窗口层能够做到减少对短波光子的吸收,从而使更多的光子被CdTe电池的吸收层吸收。     

Preparation and characterization of ZnS/CdS bi-layer for CdTe solar cell application

In this work, bilayer ZnS/CdS film was prepared as an improved window layer of CdTe solar cell. TEM was used to observe the cross section of the bilayer structure. The total thickness of ZnS/CdS film was about 60 nm, which could allow more photons to pass through it and contribute to the photocurrent. Optical properties of the bilayers were investigated using UV–vis spectroscopy. Compared with poor transmission of standard CdS film in the short wavelength range of 350–550 nm, the transmission of ZnS/CdS was improved and reached above 50%. The ZnS/CdS was annealed with CdCl₂. X-ray photoelectron spectroscopy (XPS) was used to investigate its chemical properties. A possible diffusion between CdS and ZnS was observed after annealing. The efficiency of standard CdS/CdTe solar cell was 9.53%. The device based on ZnS/CdS window layer had a poor 6% efficiency. With annealing treatment on ZnS/CdS layer, the performance was improved and reached 10.3%. In addition, the homogeneity of solar cell performance was improved using ZnS/CdS window layer. A thin ZnS layer was quite effective to reduce the possible shunt paths and short parts of window layer and consequently contributed to fabrication of a homogeneous CdTe solar cell.     

Effect of CdS deposition temperature for thermally grown Cu(In,Ga)Se2 and two-step chalcogenized Cu(In,Ga)(S,Se)2 absorbers on solar cell performances

CdS buffer layer of varying thickness ranging from 23 to 58 nm deposited at different substrate temperature were prepared as n-type junction partner for thermally grown Cu(In,Ga)Se₂ and two-step chalcogenized Cu(In,Ga)(S,Se)₂ photovoltaic absorber films and the effect of deposition temperature and time on the CdS growth behavior and solar cell performance were evaluated. High deposition temperature resulted in a thicker CdS layer and more importantly lower density and shallower depth of open voids, which attributed to the improved open-circuit voltage and fill factor due to reduced interface recombination. The solar cell efficiency of thermally grown absorber saturated at about 30 nm thickness of CdS, while that of chalcogenized absorber gradually increased with CdS thickness up to 60 nm without significant loss of short-circuit current density.     

The effects of InGaN layer thickness on the performance of InGaN/GaN p-i-n solar cells

InGaN/GaN p-i-n solar cells, each with an undoped In0.12Ga0.88N absorption layer, are grown on c-plane sapphire substrates by metal-organic chemical vapor deposition. The effects of the thickness and dislocation density of the absorp- tion layer on the collection efficiency of InGaN-based solar cells are analyzed, and the experimental results demonstrate that the thickness of the InGaN layer and the dislocation density significantly affect the performance. An optimized InGaN- based solar cell with a peak external quantum efficiency of 57% at a wavelength of 371 nm is reported. The full width at half maximum of the rocking curve of the （0002） InGaN layer is 180 arcsec.     

化学水浴法制备大面积CdS薄膜及其光伏应用

采用化学水浴法制备了大面积CdS多晶薄膜,研究了薄膜的形貌、结构和光学性质,结果表明,大面积CdS多晶薄膜具有良好的均匀性,通过优化CdS多晶薄膜,制成了不同CdS窗口层厚度的CdTe小面积太阳电池,减薄CdS薄膜可有效提高器件的短路电流,改善器件性能.随后,在面积30cm×40cm的衬底上制备了全面积为993.6cm²的CdTe太阳电池组件,其27个集成单元的电学性质较为均匀,太阳电池组件的光电转换效率8.13%. 关键词： 化学水浴法(CBD) CdS薄膜 CdTe太阳电池 CdTe太阳电池组件     

Synthesis and characterization of multiwalled carbon nanotube/CdS core/shell heterostructures

Multiwalled carbon nanotube (MWCNT)/CdS core/shell heterostructures have been successfully synthesized via a simple solution-phase method. The thickness of CdS shells can be facilely tuned by either the reaction temperature or time. The CdS nanoparticles are first formed directly on the surface of MWCNT, and then a uniform CdS sheath is yielded via orientated aggregation processes. The present work provides a simple route to obtain MWCNT-based core/shell heterostructures and thus is of wide interest for the studies of nanomaterials and nanodevices.     

基于GaSb/CdS薄膜热光伏电池的器件设计

基于GaSb薄膜热光伏器件是降低热光伏系统成本的有效途径之一, 本文主要针对GaSb/CdS薄膜热光伏器件结构进行理论分析. 采用AFORS-HET软件进行模拟仿真, 分析GaSb和CdS两种材料各自的缺陷态密度、界面态对电池性能的影响. 根据软件模拟可以得知, 吸收层GaSb的缺陷态密度以及GaSb与CdS之间的界面态密度是影响电池性能的重要因素. 当GaSb缺陷态增加时, 主要影响电池的填充因子, 电池效率明显下降. 而作为窗口层的CdS缺陷态密度对电池性能影响不明显, 当CdS缺陷态密度上升4个数量级时, 电池效率仅下降0.11%.     

Optimisation of the CBD CdS deposition parameters for ZnO/CdS/CuGaSe2/Mo solar cells

We present an optimisation of our recipe for the CdS chemical bath deposition process as applied to solar cells based on polycrystalline CuGaSe₂ (CGSe) absorber layers prepared in two stages by physical vapour deposition. We investigate the influence of the ammonia (NH₃) and the thiourea (H₂NCSNH₂) concentration, both being constituents of the chemical bath deposition (CBD) solution, at a deposition temperature of 80 °C on the microstructural and optical properties of CdS layers and on ZnO/CdS/CuGaSe₂/Mo device parameters. The composition of the CdS layers and their thickness were determined using X-ray Fluorescence Analysis. Transmission and reflection measurements performed at 300 K were used for the calculation of absorption and optical band gap energy (E_g). The E_g values of the films varied from 2.41 to 2.46 eV depending on deposition conditions. Cubic phase of the as-grown layers was identified by X-ray diffraction analysis. An improvement in the investigated solar cells efficiency was achieved when the ammonia concentration was increased and the thiourea concentration was reduced, compared to the previously used standard HMI recipe. The influence of the CBD CdS preparation recipe on the ZnO/CdS/CuGaSe₂/Mo electrical and photoelectrical properties is discussed.     

CdS quantum dot-sensitized ZnO nanorod-based photoelectrochemical solar cells

ZnO nanorods have been grown using ZnO seed layer onto ITO-coated glass substrates. CdS quantum dots have been deposited onto ZnO nanorods using simple precursors by chemical method and the assembly of CdS quantum dots with ZnO nanorod has been used as photo-electrode in quantum dot-sensitized solar cells. X-ray diffraction results show that ZnO seed layer, ZnO nanorods, and CdS quantum dot-sensitized ZnO nanorods exhibit hexagonal structure. The particle size of CdS nanoparticle is 5 nm. The surface morphology studied using scanning electron microscope shows that the top surface of the vertically aligned ZnO nanorods is fully covered by CdS quantum dots. The ZnO nanorods have diameter ranging from 100 to 200 nm. The absorption spectra reveal that the absorption edge of CdS quantum dot-sensitized ZnO nanorods shift toward longer wavelength side when compared to the absorption edge of ZnO. The efficiency of the fabricated CdS quantum dot-sensitized ZnO nanorod-based solar cell is 0.69% and is the best efficiency reported so far for this type of solar cells.     

水溶性CdTe/CdS纳米晶表面SiO2壳层的反相胶束法包覆

"提出了一种水相中制备CdTe/CdS核壳结构纳米粒子的方法.用Te粉作为碲源,用Na2S作为硫源,在50 ℃下制备了CdTe/CdS核壳结构纳米粒子. 用紫外可见吸收光谱和荧光光谱分析了CdS壳层对CdTe核的影响. 随CdS壳层厚度的增加,紫外可见吸收光谱和荧光光谱均发生了红移. CdS壳层厚度较薄时,CdTe/CdS纳米晶的荧光强度较CdTe纳米粒子有显著提高;而CdS壳层厚度较厚时,CdTe/CdS纳米晶的荧光强度会逐渐降低. 用反相胶束法在CdTe/CdS核壳结构纳米粒子的表面包被一层SiO2,     

NiO_x作为空穴传输层对有机太阳能电池光吸收的影响

基于多层膜系模型的传输矩阵方法、麦克斯韦方程和光子吸收方程,研究了NiOx作为替代3,4-乙撑二氧噻吩:聚苯乙烯磺酸盐(PEDOT:PSS)的空穴传输材料对聚3-己噻吩(P3HT)和富勒烯衍生物([6,6]-phenyl-C61-butyric acid methyl ester,PC61BM)共混体异质结有机太阳能电池器件内部光电场分布和光吸收特性的影响.分别制备了以NiOx和PEDOT:PSS为空穴传输层,P3HT:PCBM为活性层的有机太阳能电池,并通过数值模拟的方法比较了NiOx和PEDOT:PSS两种空穴传输材料对器件光伏特性的影响.结果表明:10 nm的NiOx空穴传输层器件比40 nm的PEDOT:PSS器件获得了更大的短路电流和填充因子,并具有更高的能量转化效率.     

Size-dependent electronic and optical properties of an exciton in CdSe/CdS/CdSe/CdS multilayer spherical quantum dot

The electronic and optical properties of a single exciton in a CdSe/CdS/CdSe/CdS quantum dot is studied by using effective mass approximation with parabolic confinement. The Coloumbic interaction between electron and hole is included by Hartree potential. A self-consistent technique is used to calculate the energy eigenvalue and wavefunction of exciton. Based on this approximation we investigate the effect of core size, shell thickness, well width on exciton binding energy, absorption spectra, and oscillator strength. The results provide the tuning possibility of electronic and optical properties of multilayer quantum dot with layer thickness.     

Application of multi-buffer layer of (Zn,Mg)O/CdS in Cu2ZnSn(S,Se)4 solar cells

(Zn,Mg)O (ZMO) buffer layer has attracted attention for having the potential to control the conduction band offset of buffer layer and large band-gap (Eg) Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber interface, where the ZMO layer is deposited by the sputtering. However, the solar cell efficiency is decreased with the ZMO layer as compared with the CdS layer. The decrease in conversion efficiency is attributed to the sputtering damage on the absorber and high light reflection from the surfaces of CZTSSe solar cells. To completely suppress the damage, a CdS layer with very thin thickness of 20 nm is inserted between the ZMO layer and the CZTSSe layer. In addition, MgF₂ layers are deposited on CZTSSe solar cells as anti-reflection coating. Ultimately, the solar cell with multi-buffer layer of ZMO/thin-CdS is almost same level as that with the CdS layer. Therefore, the multi-buffer layer can be an appropriate buffer layer of the large-Eg CZTSSe layer.     

Short-circuit current improvement in CdTe solar cells by combining a ZnO buffer layer and a solution back contact

Conventional CdTe solar cells have a CdS window layer, in which an absorption loss of photons with more than 2.4 eV occurs through the CdS layer. A thinner CdS layer was applied to enhance light transmission and a ZnO buffer layer with a band gap of 3.3 eV was introduced to suppress shunting through the thinner CdS window layer. A 100-nm thick ZnO layer sputter-deposited at 300 °C had uniform coverage on a transparent conductive oxide (TCO) after a subsequent high-temperature process. The ZnO layer was effective in preventing shunting through the CdS window layer so that the open-circuit voltage and fill factor of the CdTe solar cells were recovered and the short-circuit current was enhanced over that of the conventional CdTe solar cell. In the ZnO/CdS/CdTe configuration, the short-circuit current was further improved throughout the visible wavelength region by replacing the Cu-metal contact with a Cu solution contact. As a result the short-circuit current from 21.7 to 26.1 mA/cm² and the conversion efficiency of the CdTe solar cell increased from 12 to 15% without antireflective coating. Our result indicates that the Cu solution back contact is a critical factor for achieving a higher cell efficiency in addition to ZnO buffer layer.     

Photovoltaic characteristics of hybrid MEH-PPV-nanoparticles compound

Organic solar cell research has vastly developed in recent years. These organic solar cells however are still limited to low power conversion efficiencies. This has led to the generation of photovoltaic cells based on hybrid nanoparticle-organic polymer materials. The hybrid solar cell has the potential of bridging the efficiency gap which is present in organic and inorganic semiconductor materials. This paper focuses on characterization of fabricated hybrid active layer consisting of organic polymer infused with semiconductor nanoparticles. The active layer was deposited on the substrate using the spin coating technique. Materials used in the active layer are poly (2-methoxy, 5-(2-ethyl hexyloxy) p-phenyl vinylene) MEH-PPV, cadmium telluride (CdTe) and cadmium sulphide (CdS). The fabricated solar cells with active layer of MEH-PPV only were found to have a power conversion efficiency of 0.1% for 1 W, hybrid cell with active layer of MEH-PPV/CdTe has power conversion efficiency of 0.15% for 1 W and hybrid cell with active layer of MEH-PPV/CdTe/CdS has power conversion efficiency of 0.18% for 1 W.     

Growth of Cu2S/CdS nano-layered photovoltaic junctions for solar cell applications

Layered Cu₂S/CdS photovoltaic p-n junctions were fabricated via a simple and reproducible route. CdS inner layer was grown on ITO substrate using chemical bath deposition process for different times. The utilized bath consisted of cadmium sulfate and thiourea with concentrations of 0.05 M and 0.07 M, respectively. CdS layer grown for 600 min was uniform with a thickness of about 500 nm. Moreover, band gap energy of the CdS inner layers was measured as 2.40-2.44 eV depending on the thickness of the layer. Cu₂S outer layer was formed over the CdS via ion exchange chemical route, in a bath consisting of copper chloride aqueous solution. EDS, XRD, and XPS were utilized to characterize the formation of cadmium sulfide, and copper sulfide phases during the fabrication steps of the p-n junctions. Nano-layered cell, each layer 200-250 nm in thickness was fabricated with an apparent band gap of 2.22 eV. SEM imaging of both inner and the outer layers confirmed the uniformity and homogeneity of the CdS and the Cu₂S layers.     

The Dynamic Resistance of CdS/CdSe/ZnS Co-Sensitized TiO2 Solar Cells

Quantum dots' sensitized solar cells (QDSSCs) can create the high-performance and low-cost photovoltaic in the future. In this study, we synthesized the film of TiO₂/CdS/CdSe/ZnS photoanodes by successive ionic layer adsorption reaction (SILAR) method. The absorption spectra, photoluminescent spectra and electrochemical impedance spectra (EIS) of the film TiO₂/CdS/CdSe/ZnS photoanodes show that the structure of energy levels in the conduction band (CB) of photoanode materials CdS, CdSe, and ZnS quantum dots (QDs) can absorb a great number of photons in each region and inject stimulated electrons quickly into the conduction band (CB) of TiO₂. Furthermore, we also studied the influence of the SILAR cycles on the dynamic resistance, the lifetime of electrons in QDSSCs through Nyquist and Bode.     

Synthesis and characterization of CdS/PVA nanocomposite films

A series CdS/PVA nanocomposite films with different amount of Cd salt have been prepared by means of the in situ synthesis method via the reaction of Cd²⁺-dispersed poly vinyl-alcohol (PVA) with H₂S. The as-prepared films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption, photoluminescence (PL) spectra, Fourier transform infrared spectroscope (FTIR) and thermogravimetric analysis (TGA). The XRD results indicated the formation of CdS nanoparticles with hexagonal phase in the PVA matrix. The primary FTIR spectra of CdS/PVA nanocomposite in different processing stages have been discussed. The vibrational absorption peak of CdS bond at 405 cm⁻¹ was observed, which further testified the generation of CdS nanoparticles. The TGA results showed incorporation of CdS nanoparticles significantly altered the thermal properties of PVA matrix. The photoluminescence and UV-vis spectroscopy revealed that the CdS/PVA films showed quantum confinement effect.