效率为12.1%的Cu(In,Ga)Se2薄膜太阳电池

利用共蒸发的三步法制备了较高质量的四元化合物Cu(In，Ga)Se2(CIGS)薄膜，并采用Mo／CIGS／CdS／ZnO结构为基础做出转换效率超过10％的薄膜太阳电池，其最高转换效率达到12．1％(测试条件为：AM1．5，Global 1000W／m^2)。通过与国际最高水平的CIGS太阳电池各参数的比较，分析了我们所制备的CIGS太阳电池在工艺和物理方面存在的问题。     

Cu(In,Ga)Se2集成电池吸收层的三步共蒸工艺

利用三步共蒸法工艺在10cm×10cm玻璃衬底上生长出电池吸收层CuIn_(0．7)Ga_(0．3)Se_2薄膜。通过XRF和XRD谱,分析了不同预置层(Precursor)(In_(0．7)Ga_(0．3))_2Se_3生长温度下CuIn_(0．7)Ga_(0．3)Se_2薄膜的结构特性。预置层生长温度分别为300、340和400℃时,所制备的集成组件的转换效率对应为4．23%、5．16%和7．03%(测试条件为：AM1．5,1000W/cm~2)。其组件效率的提高,归因于在预置层生长温度为400℃时所制备的CuIn_(0．7)Ga_(0．3)Se_2薄膜具有良好的结构特性和组份均匀性。     

薄膜太阳电池系列讲座(3) 碲化镉(CdTe)薄膜太阳电池及其光学检测(上)

介绍了碲化镉电池的基本结构,碲化镉及其相关材料的沉积方法和基本性质,尤其是多晶材料的光学性质与其能带结构、晶粒尺寸等其他物理性质的相关性。光学检测是研究薄膜太阳电池的重要工具。通过原位椭偏学观测到的碲化镉表面粗糙度的实时演变,碲原子和硫原子的扩散,以及碲化镉、硫化镉光学性质的深层分析证明了这一手段的独特作用。     

碲化镉(CdTe)薄膜太阳电池及其光学检测(上)

介绍了碲化镉电池的基本结构,碲化镉及其相关材料的沉积方法和基本性质,尤其是多晶材料的光学性质与其能带结构、晶粒尺寸等其他物理性质的相关性.光学检测是研究薄膜太阳电池的重要工具.通过原位椭偏学观测到的碲化镉表面粗糙度的实时演变,碲原子和硫原子的扩散,以及碲化镉、硫化镉光学性质的深层分析证明了这一手段的独特作用.     

哈尔滨地区气溶胶粒子光学常数的实验研究

气溶胶广泛存在于环境中,对人的健康和气候有着不可忽略的影响,因此,对气溶胶的检测是环境科学领域的一项重要研究工作。本文采用透射法测量气溶胶粒子系的红外光谱透射率,并结合Mie理论和K-K关系式反演获得哈尔滨地区气溶胶粒子的等效光学常数,为哈尔滨地区气溶胶的监测提供数据参考。结论如下:对文献中的煤灰粒子的光学常数的反演表明本文所用反演模型是可靠的;哈尔滨地区沙尘暴天气与晴朗天气所采集的气溶胶粒子的等效光学常数变化规律基本相同,其实部在1.45和1.7之间,而虚部在0和0.3之间。     

薄膜太阳电池系列讲座(5) 碲化镉(CdTe)薄膜太阳电池及其光学检测(下)

图4碲化镉薄膜的生长条件除了氩气压强在2.5～50mTorr范围内变化外,其他沉积条件都保持一样。从图中可以看到:(1)所有薄膜在沉积初期(体层1～2nm厚)都有相对较厚的表面粗糙层。这时沉积下来的碲化镉容易聚成岛状而不是平     

Cu（In,Al）Se2薄膜太阳电池

Cu(In,Al)Se2(CIAS)化合物薄膜太阳电池属于Ⅰ-Ⅲ-Ⅵ2族化合物薄膜太阳电池,由同族的Al来替代CuInSe2(CIS)中的In,及Cu(In,Ga)Se2(CIGS)中的Ga和In。具有黄铜矿结构的Ⅰ-Ⅲ-Ⅵ2族化合物半导体材料可作为吸收层用于光伏电池。用渗入CIS中得到具有黄铜矿结构的CIGS,并且可根据Ga/(In+Ga)调节禁带宽度提高转化效率,但Ga的掺入调节禁带宽有限。以Al替代Ga,不仅可大幅降低成本,同时由于形成CuAlSe2相的能隙为2.7eV,因此调节Al/(In+Al)的比例可更宽泛地调节Cu(In,Al)Se2(CIAS)能禁带宽度。目前CIAS制备工艺以真空镀膜方法为主,包括真空蒸镀、磁控溅射、脉冲激光等。在非真空方法中,研究者们尝试了电沉积的方法成功制得单相的CIAS吸收层薄膜,而用如丝网印刷等低成本工艺CIAS薄膜尝试还少见报导。本文详细介绍了CIAS制备方法及工艺,并提出CIAS研究的一些建议。     

碲化镉(CdTe)薄膜太阳电池及其光学检测(中)

三电池结构与沉积方法碲化镉薄膜电池分为衬底朝上(阳光入射方向)和衬底朝下两大类结构。衬底朝上是目前用得最多的结构。其生长过程是在玻璃衬底上顺序沉积透明导电氧化物(TCO)、硫化镉、碲化镉以及金属背电极层。     

Cu(In,Ga)Se2 based photovoltaic structure by electrodeposition and processing

CuIn_1−xGa_xSe₂ (CIGS) thin films were formed from an electrodeposited CuInSe₂ (CIS) precursor by thermal processing in vacuum in which the film stoichiometry was adjusted by adding In, Ga and Se. The structure, composition, morphology and opto-electronic properties of the as-deposited and selenized CIS precursors were characterized by various techniques. A 9.8% CIGS based thin film solar cell was developed using the electrodeposited and processed film. The cell structure consisted of Mo/CIGS/CdS/ZnO/MgF₂. The cell parameters such as J_sc, V_oc, FF and η were determined from I–V characterization of the cell.     

Improved Cu(In,Ga)(S,Se)2 thin film solar cells by surface sulfurization

Surface sulfurization was developed as a technique for fabricating efficient ZnO : Al/CdS/graded Cu(In,Ga)(S,Se)₂/ Mo/glass solar cells. Prior to the sulfurization, single-graded Cu(In,Ga)Se₂ (CIGS) films were deposited by a multi-stage process. The sulfurization of CIGS films was carried out using a H₂S---Ar mixture at elevated temperatures. The crystallographic and compositional properties of the absorber layers were investigated by XRD, SEM and AES analyses. After sulfurization, sulfur atoms were substituted for selenium atoms at the surface layer of CIGS films to form a Cu(In,Ga)(S,Se)₂ absorber layer. The diffusion of sulfur depends strongly on the grain structure of CIGS film. The cell efficiency of the 8–11% range before sulfurization was improved dramatically to 14.3% with V_oc = 528 mV, J_sc = 39.9 mA/cm² and FF = 0.68 after the sulfurization process.     

柔性不锈钢衬底CIGS薄膜太阳电池

以轻质柔性不锈钢材料为衬底,利用三步共蒸发法制备较高质量的四元化合物Cu(In,Ga)Se_2薄膜,CIGS层在Mo导电层上具有很强的附着力。利用XRD和XRF分别分析了所制备薄膜的晶相和组分。以ZnO:Al/i-ZnO/ CdS/CIGS/Mo/Stainless steel结构为基础得到最高转换效率为9.39%的柔性太阳电池。最后讨论了衬底粗糙度、有害杂质的扩散和不含有Na元素等不利因素对于电池性能的影响。     

铜铟镓硒柔性薄膜太阳电池碱金属掺杂技术进展

便携式充能市场的发展带来对柔性电池的增量需求,铜铟镓硒（CIGS）薄膜电池是目前市场上主要应用的柔性电池,极具发展前景。介绍了铜铟镓硒柔性薄膜电池碱金属掺杂工艺技术的发展,分析了碱金属掺杂对电池效率提升的影响以及在产业化中存在的问题,并从工艺研究、设备制造和掺杂机理等方面对碱金属掺杂技术的进一步发展提出了建议。     

Formation of CuInSe2 and Cu(In,Ga)Se2 films by electrodeposition and vacuum annealing treatment

Polycrystalline thin films of CuInSe₂ and Cu(In,Ga)Se₂ (CIGS) were grown on both polished Mo substrates and Mo-coated glass substrates by one-step electrodeposition. All the as-deposited films have been annealed in vacuum at 450°C for a short time to improve the crystalline properties. The films have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The results indicate that the crystallization of the films was greatly improved after annealing. Further more, a CIGS film with 23 at% Ga was obtained.     

Photoconductivity of Cu(In, Ga) Se2 films

Polycrystalline CuIn_{1 − x}Ga_xSe₂ (0 ≤ x < 0.3) films (CIGS) were deposited by coevaporating the elements from appropriate sources onto glass substrates (substrate temperature 720 to 820 K). Photoconductivity of the polycrystalline CIGS films with partially depleted grains were studied in the temperature range 130–285 K at various illumination levels (0–100 mW/cm²). The data at low temperature (T < 170 K) were analyzed by the grain boundary trapping model with monovalent trapping states. The grain boundary barrier height in the dark and under illumination were obtained for different x-values of CuIn_1−xGa_xSe₂ films. Addition of Ga in the polycrystalline films resulted in a significant decrease in the barrier height. Variation of the barrier height with incident intensity indicated a complex recombination mechanism to be effective in the CIGS films.     

Novel device structure for Cu(In,Ga)Se2 thin film solar cells using transparent conducting oxide back and front contacts

Cu(In_1−xGa_x)Se₂ (CIGS)-based thin film solar cells fabricated using transparent conducting oxide (TCO) front and back contacts were investigated. The cell performance of substrate-type CIGS devices using TCO back contacts was almost the same as that of conventional CIGS solar cells with metallic Mo back contacts when the CIGS deposition temperatures were below 500 °C for SnO₂:F and 520 °C for ITO. CIGS thin film solar cells fabricated with ITO back contacts had an efficiency of 15.2% without anti-reflection coatings. However, the cell performance deteriorated at deposition temperatures above 520 °C. This is attributed to the increased resistivity of the TCO’s due to the removal of fluorine from SnO₂ or undesirable formation of a Ga₂O₃ thin layer at the CIGS/ITO interface. The formation of Ga₂O₃ was eliminated by inserting an intermediate layer such as Mo between ITO and CIGS. Furthermore, bifacial CIGS thin film solar cells were demonstrated as being one of the applications of semi-transparent CIGS devices. The cell performance of bifacial devices was improved by controlling the thickness of the CIGS absorber layer. Superstrate-type CIGS thin film solar cells with an efficiency of 12.8% were fabricated using a ZnO:Al front contact. Key techniques include the use of a graded band gap Cu(In,Ga)₃Se₅ phase absorber layer and a ZnO buffer layer along with the inclusion of Na₂S during CIGS deposition.     

X-ray fluorescence investigation of the Ga distribution in Cu(In,Ga)Se2 thin films

The efficiencies of Cu(In,Ga)Se₂/CdS/ZnO solar cell devices in which the absorbers are produced by classical two-step processes are significantly lower that those in which co-evaporated absorbers are used. A significant problem related to two-step growth processes is the reported segregation of Ga towards the Mo back contact, resulting in separate CuInSe₂ and CuGaSe₂ phases. Furthermore, it is often reported that material losses (especially In and Ga) occur during high-temperature selenization of metallic precursors. In this study, X-ray fluorescence (XRF) analysis was used to study the diffusion behaviour of the chalcopyrite elements in single-stage and two-stage processed Cu(In,Ga)Se₂ thin films. This relatively simple characterization technique proved to be very reliable in determining the degree of selenium incorporation, possible material losses and the in-depth compositional uniformity of samples at different stages of processing. This information is especially important in the case of two-stage growth processes, involving high-temperature selenization steps of metallic precursors. Device quality Cu(In,Ga)Se₂ thin films were prepared by a relatively simple and reproducible two-step growth process in which all the metals were evaporated from one single crucible in a selenium-containing environment. The precursors were finally treated in an H₂Se/Ar atmosphere to produce fully reacted films. XRF measurement indicated no loss of In or Ga during this final selenization step, but a significant degree of element diffusion which depended on the reaction temperature. It was also possible to produce Cu(In,Ga)Se₂ thin films with an appreciable amount of Ga in the near-surface region without separated CuInSe₂ and CuGaSe₂ phases.     

Analysis of Cu(In,Ga)(S,Se)2 thin-film solar cells by means of electron microscopy

The present work gives an overview of how electron microscopy and its related techniques are used to analyze individual layers and their interfaces in Cu(In,Ga)(S,Se)₂ thin-film solar cells. Imaging of samples can be performed at scales of down to the (sub)angstroms range. At similar spatial resolutions, information on composition can be gathered by means of energy-dispersive X-ray spectroscopy (EDX) and on spatial distributions of electrostatic Coulomb potentials in the specimen by applying electron holography. Microstructural and compositional properties as well as charge-carrier collection and radiative recombination behavior of the individual layers are accessible by use of electron backscatter diffraction, EDX, electron-beam-induced current (EBIC) and cathodoluminescence measurements, available in scanning electron microscopy. The present contribution gives an overview of the various scanning and transmission electron microscopy techniques applied on Cu(In,Ga)(S,Se)₂ thin-film solar cells, examples from case studies, and also demonstrates how these techniques may be combined in order to improve the analysis. Particularly, EBIC results show a reduced charge-carrier collection at Cu(In,Ga)Se₂ grain boundaries, while no indication was found for a charge accumulation at the grain boundaries by electron holography.     

Highly efficient Cu(In,Ga)Se2 mini-modules

In this contribution, we present results and the philosophy of our mini-module efforts. These efforts have achieved world record levels as well as a reproducible process. Various mini-module designs are tested using two different baseline Cu(In,Ga)Se₂ deposition recipes. Gridded mini-modules achieve highest efficiencies and are much less demanding on the ZnO:Al top contact than their conventional counterpart. For all of the designs tested, our experimental results are in the order of the expectations from our modeling. Gridded modules can achieve efficiency levels very close to those of the cells.