具有高阻抗本征SnO2过渡层的CdS/CdTe多晶薄膜太阳电池

采用超声喷雾热解法制备了具有高阻抗的本征SnO2透明导电膜,将其运用在CdS层减薄了的CdS/CdTe多晶薄膜太阳电池中,对减薄后的CdS薄膜进行了XRD,AFM图谱分析,并对电池进行了光、暗I-V,光谱响应和C-V测试.结果表明,在高阻膜上沉积的减薄CdS薄膜(111)取向更明显,但易形成微孔.引入高阻层后,能消除CdS微孔形成的微小漏电通道,有效保护p-n结,改善了电池的并联电阻、填充因子和短波响应,使载流子浓度增加,暗饱和电流密度减小,从而电池性能得到改善,电池转换效率增加了14.4%.     

具有高阻抗本征SnO2过渡层的CdS/CdTe多晶薄膜太阳电池

采用超声喷雾热解法制备了具有高阻抗的本征SnO₂透明导电膜，将其运用在CdS层减薄了的CdS/CdTe多晶薄膜太阳电池中，对减薄后的CdS薄膜进行了XRD,AFM图谱分析，并对电池进行了光、暗I-V，光谱响应和C-V测试.结果表明，在高阻膜上沉积的减薄CdS薄膜(111)取向更明显，但易形成微孔.引入高阻层后，能消除CdS微孔形成的微小漏电通道，有效保护p-n结，改善了电池的并联电阻、填充因子和短波响应，使载流子浓度增加，暗饱和电流密度减小，从而电池性能得到改善，电池转换效率增加了14.4%. 关键词： CdTe电池 过渡层 效率     

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     

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。     

CdTe太阳电池前电极SnO2:F/SnO2复合薄膜性能分析

减薄CdS窗口层是提高CdS/CdTe太阳电池转换效率的有效途径之一,减薄窗口层会对器件造成不利的影响,因此在减薄了的窗口层与前电极之间引入过渡层非常必要.利用反应磁控溅射法在前电极SnO₂:F薄膜衬底上制备未掺杂的SnO₂薄膜形成过渡层,并将其在N₂/O₂=4 ∶1,550 ℃环境进行了30 min热处理,利用原子力显微镜、X射线衍射仪、紫外分光光度计对复合薄膜热处理前后的形貌、结构、光学性能进行了表征,同时分析了复     

氧对于在Ar/O氛围下用近空间升华法制备的CdS薄膜的影响

采用近空间升华法（CSS）在氩/氧气氛中制备了硫化镉（CdS）多晶薄膜.利用XRD,XPS,AFM,UV-VIS光谱和四探针技术等测试和分析手段系统研究了氧对薄膜的成分、结构、光学和电学等性质的影响.结果表明,用近空间升华法制备的CdS薄膜具有六方相结构,膜层致密、均匀,平均晶粒大小约为40 nm,富硫.氧掺入后部分与镉生成氧化镉,并随着氧含量的增加,薄膜的成分有趋于化学计量比的趋势,光学带隙加宽,光暗电导比增加.此外,还利用扫描电镜（SEM）观察了CdS/CdTe断面结合光谱响应（QE）的结果讨论了氧对CdS/CdTe界面互扩散的影响.发现,随着CdS薄膜制备气氛中氧分压的升高,CdS/CdTe界面的互扩散程度降低,有利于提高器件在500—600 nm波长范围内的光谱响应.认为,氧含量的增加不但使CdS薄膜在光伏应用方面的质量得到改善,而且CdTe太阳电池器件中的CdS/CdTe界面也得到了优化. 关键词： CdS多晶薄膜 近空间升华法 窗口层 界面     

不同环境下硫化镉/铜基薄膜异质结退火对太阳电池性能调控

高效铜基薄膜太阳电池通常采用无机n型半导体材料CdS作为缓冲层,因此,缓冲层与吸收层之间的界面质量和能带匹配对载流子的收集利用至关重要.在优化CdS基础工艺的基础上,在含硫气氛下对硫化镉/铜基薄膜异质结进行退火的策略进一步提高CdS薄膜质量,并将其应用到铜基太阳电池,调控铜基薄膜电池p-n异质结能带匹配.研究表明, CdS薄膜在含硫的惰性气氛中退火可以有效提高CdS薄膜的结晶质量并抑制CZTS/CdS异质结界面的非辐射复合,器件的开路电压得到大幅提升,最高可达718 mV.在器件效率方面,基于溅射法的CZTS太阳电池效率从3.47%提升到5.68%,约为不退火处理的2倍.该研究为铜基薄膜太阳电池器件实现高开路电压提供了可靠的工艺窗口.同时,有力地说明了退火气氛选择对于CdS质量以及CZTS/CdS异质结能带匹配的重要性,除了界面互扩散以外,对薄膜材料组分及其结晶性等均实现了调控.     

近空间升华法制备CdS多晶薄膜的研究

系统地研究了近空间升华法(CSS)制备CdS薄膜沉积速率的影响因素。发现CdS薄膜的沉积速率随升华源温度的升高而增大,但随衬底温度和沉积气压的上升而下降。对所制备样品的结构、表面形貌和光谱透过率特性进行了测试,结果表明：(1)不同氧分压下沉积的CdS薄膜沿(103)晶向择优生长。CdCl₂氛围下退火后,(103)晶向的优势得到进一步加强;(2)不同氧分压制备的CdS薄膜致密且粒径均匀,晶粒的大小随着衬底温度的升高而增大,但薄膜的粗糙度也随之增大;(3)随着CdS薄膜厚度的减小,可见光中短波段的透过率有所增大,有利于提高太阳电池的短波光谱响应。并将CSS制备的CdS多晶薄膜用于CdTe太阳电池的制作,获得了10.29%的光电转换效率,初步验证了该制作工艺的可行性。     

磁控溅射Cl掺杂CdTe薄膜的孪晶结构与电学性质

CdTe用作薄膜太阳能电池吸收层需要经过氯处理才能得到高的光电转换效率,其中Cl原子的作用机理仍然没有完全被理解.实验发现Cl原子主要偏聚在CdTe晶界处,对晶界有钝化作用,而有第一性原理计算认为Cl原子掺入CdTe晶格能够引入浅能级提高光电转换效率.为了验证Cl原子掺杂是否对CdTe的光电转换效率有益,本文通过磁控溅射制备了100 ppm(ppm=1/1000000)Cl原子掺杂的CdTe(CdTe:Cl)薄膜并研究了薄膜的晶体结构与电学性质,同时对比了正常氯处理的无掺杂CdTe薄膜与CdTe:Cl薄膜之间的性质区别.实验发现Cl原子掺杂会在CdTe:Cl中形成大量仅由几个原子层构成的孪晶,电子和空穴在CdTe:Cl薄膜中没有分离的传导通道,而在氯处理后的CdTe薄膜中电子沿晶界传导,空穴沿晶粒内部传导.磁控溅射沉积的CdTe:Cl多晶薄膜属于高阻材料,退火前载流子迁移率很低,退火后载流子浓度降低到本征数量级,电阻率提高.CdTe:Cl薄膜电池效率远低于正常氯处理的无掺杂CdTe薄膜电池效率.磁控溅射制备的非平衡重掺杂CdTe:Cl多晶薄膜不适合用作薄膜太阳能电池的吸收层.     

连续离子层吸附反应沉积后硫化法制备柔性铜锌锡硫薄膜太阳电池

在柔性钼箔衬底上采用连续离子层吸附反应法(successive ionic layer absorption and reaction)制备ZnS/Cu2SnSx叠层结构的预制层薄膜,预制层薄膜在蒸发硫气氛、550 C温度条件下进行退火得到Cu2ZnSnS4吸收层.分别采用EDS,XRD,Raman,SEM表征吸收层薄膜的成分、物相和表面形貌.结果表明,退火后薄膜结晶质量良好,表面形貌致密.用在普通钠钙玻璃上采用相同工艺制备的CZTS薄膜表征薄膜的光学和电学性能,表明退火后薄膜带隙宽度为1.49 eV,在可见光区光吸收系数大于104cm 1,载流子浓度与电阻率均满足薄膜太阳电池器件对吸收层的要求.用上述柔性衬底上的吸收层制备Mo foil/CZTS/CdS/i-ZnO/ZnO:Al/Ag结构的薄膜太阳电池得到2.42%的效率,是目前报道柔性CZTS太阳电池最高效率.     

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.     

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.     

Impact of thermal annealing on physical properties of vacuum evaporated polycrystalline CdTe thin films for solar cell applications

A study on impact of post-deposition thermal annealing on the physical properties of CdTe thin films is undertaken in this paper. The thin films of thickness 500 nm were grown on ITO and glass substrates employing thermal vacuum evaporation followed by post-deposition thermal annealing in air atmosphere within low temperature range 150–350 °C. These films were subjected to the XRD, UV‐Vis NIR spectrophotometer, source meter, SEM coupled with EDS and AFM for structural, optical, electrical and surface topographical analysis respectively. The diffraction patterns reveal that the films are having zinc-blende cubic structure with preferred orientation along (111) and polycrystalline in nature. The crystallographic parameters are calculated and discussed in detail. The optical band gap is found in the range 1.48–1.64 eV and observed to decrease with thermal annealing. The current–voltage characteristics show that the CdTe films exhibit linear ohmic behavior. The SEM studies show that the as-grown films are homogeneous, uniform and free from defects. The AFM studies reveal that the surface roughness of films is observed to increase with annealing. The experimental results reveal that the thermal annealing has significant impact on the physical properties of CdTe thin films and may be used as absorber layer to the CdTe/CdS thin films solar cells.     

CdTe多晶薄膜沉积制备及其性能

在氩气和氧气混合气氛下,近空间升华法制备了CdTe多晶薄膜。薄膜的结构、性质决定于整个沉积过程。深入研究沉积过程中的热交换、物质输运,有助于获得结构致密具有良好光电性质的CdTe薄膜。分析了近空问沉积的物理机制,测量了近空间沉积装置内的温度分布,讨论了升温过程、气压与薄膜的初期成核的关系。结果表明,不同气压下制备的样品,均有立方相CdTe。此外,还有CdS和SnO2：F衍射峰。CdTe晶粒随气压增加有减小趋势;随气压的增加,透过率呈下降趋势,相应的CdTe吸收边向短波方向移动。采用衬底温度500℃,源温度620℃,在120℃的温差下,沉积时间4min上制备CdTe多晶薄膜,获得转换效率优良的结构为SnO2：F／CdS／CdTe／Au的集成电池。     

Performance improvement in CdTe solar cells by modifying the CdS/CdTe interface with a Cd treatment

The performance of n-CdS/p-CdTe solar cells is often degraded under light soaking or thermal stress, even though the technology of CdTe solar cells is close to a commercial level. The Cu diffusion from a Cu back contact to a CdS window layer might degrade the cell's performance. To prevent the Cu diffusion, a very-thin intrinsic CdTe layer was introduced at the n-CdS/p-CdTe interface by depositing a very-thin Cd metal layer on the CdS film and converting the Cd metal into intrinsic CdTe during p-CdTe deposition at high temperature. By the Cd treatment on CdS surface, pinholes or voids were eliminated at the CdS/CdTe and the intermixing of Te and S at the interface was much suppressed. The depletion width was much increased and the intensity of LTPL peak was increased. The analysis suggested that an intrinsic CdTe interlayer was formed and the surface recombination rate was suppressed by the intrinsic interlayer. As a result, the short circuit current of the CdTe solar cell was significantly increased due the increased current gain in the blue wavelength region. The thermal stability of the CdTe solar cell was also greatly improved and the Cu diffusion was retarded by the intrinsic CdTe interlayer at the n-CdS/p-CdTe.     

Numerical simulation of ultra-thin CdTe solar cells with a buffer layer of MoOx in the backwall configuration

The software of Solar Cell Capacitance Simulator (SCAPS) is used to investigate the performance of ultra-thin CdTe solar cells in the backwall configuration (glass/ITO/MoO_x/CdTe/CdS/SnO₂/Ag). The backwall structure utilizes ultra-thin CdTe absorber layer instead of CdS film facing light illumination, which eliminates the absorption of CdS in short-wavelength region and improves the blue response of CdTe. A buffer layer of MoO_x is added to modify the contact between CdTe and ITO, reducing the valence band barrier height and simultaneously forming an electron reflector, which can reduce electron-hole recombination at this contact. When the thickness of MoO_x is 2 nm, the simulation results show that an efficiency can reach up to 25.5% with high ITO work function and ideal interface recombination velocity.