PLD法制备ZnO/Si异质结的I-V特性研究

用脉冲激光沉积法分别在不同电阻率的p型和n型Si( 100)衬底上制备了不掺杂ZnO薄膜,相应制成n-ZnO/p-Si和n-ZnO/n-Si异质结器件.利用X射线衍射和原子力显微镜对ZnO薄膜进行的结构和形貌测试表明,薄膜结晶情况良好,具有高度的c轴择优取向,表面颗粒大小、分布均匀.对器件的I-V特性测试表明,在无光条件下,制备的n-ZnO/p-Si异质结漏电流很低,而n-ZnO/n-Si同型异质结漏电流要稍大一些;随衬底电阻率的增大,上述器件的阈值电压变小;器件在光照下的漏电流明显比无光条件下的要大.     

SiGe/Si异质结光电器件

SiGe/Si异质结光电器件及其光电集成(OEIC)是硅基光电研究的一个非常引人注目的领域.综述了SiGe/Si异质结材料的基本性质,SiGe/Si异质结光电器件的结构、性能、应用及其光电集成.重点介绍了SiGe/Si光电探测器及其与其他相关器件的集成.     

Mg2Si／Si异质结的制备

采用射频磁控溅射和低真空退火方法制备Mg2Si／Si异质结,首先在n型Si（111）衬底上沉积Mg膜,经低真空退火形成Mg2Si／Si异质结,Mg膜厚度约为484nm,退火后形成的Mg2Si薄膜厚度约400nto,利用xRD和sEM分别研究了Mg2Si薄膜的晶体结构和表面形貌,霍尔效应结果表明,制备的Mg2Si薄膜呈现n型导电特性。     

β-FeSi2/Si异质结的制备及性质研究

采用直流磁控溅射和真空退火方法制备β-FeSi2/Si异质结,首先在n型Si(100)衬底上沉积Fe膜,经真空退火形成β-FeSi2/Si异质结,Fe膜厚度约238nm,退火后形成的β-FeSi2薄膜厚度约为720nm。利用XRD、SEM和红外光谱仪分别研究了β-FeSi2薄膜的晶体结构、表面形貌和光学性质。霍尔效应结果表明,制备的β-FeSi2薄膜为n型导电,载流子浓度为9.51×1015cm-3,电子迁移率为380cm2/(V.s)。     

β-FeSi2/Si异质结的伏安特性分析

用磁控溅射方法制备β-FeSi2/Si异质结,在分析其伏安特性的基础上探索其是否适合制备红外探测器,XRD、SEM分析表明,该方法能得到纯净、表面平整的β-FeSi2/Si薄膜;在室温下异质结的I—V特性具有很好的整流特性,整流效率约为Idirect／Ireverse～10^2,分流电阻约为38．4kΩ,零偏压下的电流响应率约为26μA／W。推算结果表明,该异质结的红外探测率约为1．479×10^9cm·√Hz/W,适合用于制备红外探测器。     

Cu2ZnSnS4/Bi2FeCrO6半导体异质结的脉冲激光沉积法制备及其光电性能

为充分发挥无机铁电氧化物双钙钛矿Bi2FeCrO6(BFCO)的光电特性,选择P型半导体化合物Cu2ZnSnS4(CZTS)作为空穴传输层与BFCO结合,构建半导体异质结.采用脉冲激光沉积法(PLD)制备得到上述两种多元化合物薄膜,SEM,AFM,EDS及XRD测试结果可证明所得产物形貌均匀致密、且符合化学计量比;原位逐层沉积技术可以抑制异质结界面缺陷和杂质的产生.着重研究了沉积温度及不同基底对薄膜性能的影响.采用基于可见光吸收谱的测试和Tauc方法分别估算BFCO和CZTS薄膜的禁带宽度,结果分别为2.23 eV和1.49 eV.研究结果表明:该异质结具有良好的整流特性;当电场强度在0.5 kV/cm到2.0 kV/cm之间时,结构漏电机制符合Schottky发射模型.     

溶剂热法制备Cu2ZnSnS4粉末及其表征

采用溶剂热法, 以CuCl₂·2H₂O、Zn(Ac)₂·2H₂O、SnCl₄·5H₂O作金属源, 硫脲作硫源, 乙二醇作溶剂, PVP作表面活性剂, 制备了Cu₂ZnSnS₄(CZTS)粉末。利用XRD、SEM、Raman、TEM、EDS、UV-Vis吸收光谱探讨了反应温度和反应时间对制备CZTS粉末的相结构、成分、形貌以及光学性能的影响。结果表明: 反应温度和反应时间对CZTS粉末的颗粒形貌和光学性能影响较大, 最佳合成温度为230℃, 反应时间24 h。该条件下生成的CZTS粉末相较为纯净、结晶完全, 形貌为表面嵌有薄片的微球, 各元素原子比接近化学计量比, 光学带隙为1.52 eV, 与太阳能电池所需的最佳带隙接近。并对其形成机理进行了初步探讨。     

近红外Mg2Si/Si异质结光电二极管的结构设计与仿真

本工作设计了近红外Mg_2Si/Si异质结光电二极管的器件结构,并采用Silvaco-TCAD对器件主要性能参数(包括光谱响应、暗电流等)进行模拟仿真,优化了器件的结构参数和工艺参数。仿真结果表明:所设计的pin型光电二极管在波长为0. 6～1. 5μm时比pn型光电二极管具有更高的响应度,峰值波长为1. 11μm时,响应度最高达到0. 742 A·W~(-1),1. 31μm处响应度为0. 53 A·W~(-1)。pin型光电二极管的暗电流密度较pn型光电二极管略大,约为1×10~(-6)A·cm~(-2)。Mg2_Si/Si异质结中间界面态密度也不宜超过1×10~(11)cm~(-2)。     

Mg掺杂Cu2ZnSnS4的第一性原理研究

采用基于密度泛函理论(DFT)的第一性原理对光伏材料Cu₂ZnSnS₄ (CZTS)掺Mg进行了研究。通过建立Mg取代CZTS中Cu、Zn和Sn的点缺陷结构, 计算Mg掺杂缺陷的生成能及对CZTS电子结构的影响。计算结果表明掺Mg不引入深能级缺陷也不改变材料的禁带宽度; 并且富Sn条件更有利于Mg取代Cu形成施主缺陷, 使p型转变为n型。本研究可为CZTS太阳能电池掺Mg的应用研究提供理论基础。     

退火温度对ZnO/Si异质结光电转换特性的影响

采用直流反应溅射法在P-Si(100)衬底上制备了ZnO薄膜,XRD测量表明ZnO为沿c轴高度取向的多晶薄膜,1-V特性曲线表明,ZnO/Si异质结具有明显的整流特性.研究了退火温度对异质结光电转换特性的影响,结果显示,合适的退火温度能显著增大异质结的开路电压和短路电流,进而增大异质结的光电转换效率,经400℃退火后异质结获得最佳的转换效率.当退火温度达到或超过500℃时,异质结的反向电流迅速增加,光生电压和光生电流大幅度减小.通过对ZnO薄膜结构和电学性质的测量和分析,推测异质结的光电转换特性改变主要受ZnO薄膜的电学性质影响.     

Fabrication and characterization of Cu2ZnSnS4 thin films deposited by spray pyrolysis technique

We have investigated synthesis conditions and some properties of sprayed Cu₂ZnSnS₄ (CZTS) thin films in order to determine the best preparation conditions for the realization of CZTS based photovoltaic solar cells. The thin films are made by means of spraying of aqueous solutions containing copper chloride, zinc chloride, tin chloride and thiourea on heated glass substrates at various temperatures. In order to optimize the synthesis conditions of the CZTS films, two series of experiments are performed. In the first series the sprayed duration was fixed at 30 min and in the second it is fixed at 60 min. In each series, the substrate temperature was changed from 553°K to 633°K. The X-ray diffraction shows, on one hand, that the best crystallinity was obtained for 613°K as substrate temperature and 60 min as sprayed duration. On the other hand, these CZTS films exhibit the kesterite structure with preferential orientation along the [112] direction. Atomical Force Microscopy was used to determine the grain sizes and the roughness of these CZTS thin film. After the annealing treatment, we estimated the optical band-gap energy of the CZTS thin film exhibiting the best crystallinity as 1.5 eV which is quite close to the optimum value for a solar cell.     

Growth and Raman scattering characterization of Cu2ZnSnS4 thin films

In the present work we report the results of the growth, morphological and structural characterization of Cu₂ZnSnS₄ (CZTS) thin films prepared by sulfurization of DC magnetron sputtered Cu/Zn/Sn precursor layers. The adjustment of the thicknesses and the properties of the precursors were used to control the final composition of the films. Its properties were studied by SEM/EDS, XRD and Raman scattering. The influence of the sulfurization temperature on the morphology, composition and structure of the films has been studied. With the presented method we have been able to prepare CZTS thin films with the kesterite structure.     

溶胶-凝胶法制备铜锌锡硫薄膜及其太阳能电池的研究进展

原料丰富价廉的铜锌锡硫(Cu2ZnSnS4,CZTS)材料与非真空、低成本绿色溶胶-凝胶法相结合在产业化制造高性价比CZTS薄膜太阳能电池方面的应用引人关注。为了了解未来发展方向,综述了溶胶-凝胶法制备CZTS薄膜与器件的研究进展,讨论了不同溶胶-凝胶工艺途径、不同溶剂、硫化等对CZTS薄膜制备与器件特性的影响,分析了Na掺杂及硫化退火对CZTS薄膜的作用,并结合绿色制造的要求探讨了其发展趋势。     

Multi-stage evaporation of Cu2ZnSnS4 thin films

Multi-stage evaporation is a well-established method for the controlled growth of chalcopyrite thin films. To apply this technique to the deposition of Cu₂ZnSnS₄ thin films we investigated two different stage sequences: (A) using Cu₂SnS₃ as precursor to react with Zn-S and (B) using ZnS as precursor to react with Cu-Sn-S. Both Cu₂SnS₃ and ZnS are structurally related to Cu₂ZnSnS₄. In case (A) the formation of copper tin sulphide in the first stage was realized by depositing Mo/SnS_x/CuS (1 < x < 2) and subsequent annealing. In the second stage ZnS was evaporated in excess at different substrate temperatures. We assign a significant drop of ZnS incorporation at elevated temperatures to a decrease of ZnS surface adhesion, which indicates a self-limited process with solely reactive adsorption of ZnS at high temperatures. In case (B) firstly ZnS was deposited at a substrate temperature of 150 °C. In the second stage Cu, Sn and S were evaporated simultaneously at varying substrate temperatures. At temperatures above 400 °C we find a strong decrease of Sn-incorporation and also a Zn-loss in the layers. The re-evaporation of elemental Zn has to be assumed. XRD measurements after KCN-etch on the layers prepared at 380 °C show for both sample types clearly kesterite, though an additional share of ZnS and Cu₂SnS₃ can not be excluded. SEM micrographs reveal that films of sample type B are denser and have larger crystallites than for sample type A, where the porous morphology of the tin sulphide precursor is still observable. Solar cells of these absorbers reached conversion efficiencies of 1.1% and open circuit voltages of up to 500 mV.     

Synthesis and characterization of Cu2ZnSnS4 absorber layers by an electrodeposition-annealing route

An electrodeposition-annealing route to films of the promising p-type absorber material Cu₂ZnSnS₄ (CZTS) using layered metal precursors is studied. The dependence of device performance on composition is investigated, and it is shown that a considerable Cu-deficiency is desirable to produce effective material, as measured by photoelectrochemical measurements employing the Eu^3+/2+ redox couple. The differing effects of using elemental sulphur and H₂S as sulphur sources during annealing are also studied, and it is demonstrated that H₂S annealing results in films with improved crystallinity.     

Cu2ZnSnS4纳米颗粒及其薄膜的制备与表征

采用热注入法,在油胺(OLA)中合成出Cu2ZnSnS4(CZTS)纳米颗粒,并在玻璃衬底上制备了薄膜,研究了不同合成温度对纳米颗粒生成的影响.通过X射线衍射仪、拉曼光谱仪、透射电子显微镜、扫描电子显微镜、紫外可见分光光度计对所得纳米晶材料的结构与成分、颗粒大小与形貌、光吸收谱进行了测试分析.研究结果表明:采用热注入法的最佳合成温度在260℃左右,该温度下生成的多晶CZTS纳米颗粒尺寸约10 nm,分散性良好,光学禁带宽度约1.5 eV.     

Cu2ZnSnS4 solar cell prepared entirely by non-vacuum processes

Cu₂ZnSnS₄ (CZTS) solar cell with superstrate structure of fluorine-doped tin oxide glass/TiO₂/In₂S₃/CZTS/Carbon was prepared entirely by non-vacuum processes. The compact TiO₂ window and In₂S₃ buffer layers, CZTS absorber layer and Carbon electrode layer were prepared by spray pyrolysis method, ball milling and screen printing combination processes and screen printing process, respectively. The short-circuit current density, open-circuit voltage, fill factor and conversion efficiency of the best fabricated solar cell are 8.76 mA/cm², 250 mV, 0.27 and 0.6%, respectively. The fabrication process for the CZTS solar cell did not employ any vacuum conditions or high-toxic materials (such as CdS, H₂Se, H₂S or Se).     

Growth of Cu2ZnSnS4 thin films on Si (100) substrates by multisource evaporation

Cu₂ZnSnS₄ films were grown on Si (100) by vacuum evaporation using elemental Cu, Sn, S and binary ZnS as sources. X-ray diffraction patterns of films grown at different substrate temperatures indicated that polycrystalline growth was suppressed and the orientational growths were relatively induced in a film grown at higher temperatures. Tetragonal structure of Cu₂ZnSnS₄ films was confirmed by studying RHEED patterns. The existence of c-axis ([001] direction) growth, two kinds of a-axis (〈100〉 direction) growth and four kinds of {112} twins which can be classified as two symmetrical pairs is proposed. Broad emissions at around 1.45 eV and 1.31 eV were observed in the photoluminescence spectrum measured at 13 K.     

阳离子部分取代Cu2ZnSnS4的研究进展

P型半导体Cu_2ZnSnS_4(CZTS)由于具有最佳的直接带隙(1.0~1.5eV)、高的光吸收系数(超过104 cm~(-1))以及丰富、无毒的元素组成,使其成为商业化低成本太阳能电池最有希望的候选材料之一。然而,材料本身的一些缺陷制约了CZTS薄膜太阳能电池效率的提高。为了提高CZTS薄膜太阳能电池的效率,研究者们使用其他阳离子部分取代Cu、Zn或Sn来改善CZTS的缺陷。从CZTS的3种不同取代位置出发,综述了近年来各种阳离子部分取代CZTS的研究进展,同时对阳离子部分取代CZTS材料的发展前景进行了展望。     

Single step synthesis of chalcogenide nanoparticles Cu2ZnSnS4, Cu2FeSnS4 by thermal decomposition of metal precursors

Cu₂ZnSnS₄ (CZTS) and Cu₂FeSnS₄ (CFTS) nanoparticles were synthesized by thermal decomposition of metal precursors. Dispersion of the precursors in the solvent prior to reaction significantly lowered the temperature and time required for the reaction. Extensive characterization of the synthesized nanoparticles was done. Materials characteristics of the synthesized nanoparticles such as elemental composition, band gap and morphology were found to be similar to the nanoparticles prepared by conventional synthesis techniques.