【作者】 褚家宝；

【导师】 孙卓； 黄素梅；

【作者基本信息】 华东师范大学 ， 纳米物理学， 2009， 博士

【摘要】 铜铟镓硒Cu（InGa）Se₂（CIGS）薄膜太阳能电池,具有转换效率高、成本低、稳定性好等特点,是最有发展前景的薄膜太阳能电池之一。到目前为止,基于三步共蒸发工艺制备的CIGS薄膜太阳能电池的效率已达19.99%,是所有薄膜太阳能电池中最高的。尽管这种制备方法有很多优点,制备成分均匀的大面积电池却具有难以克服的困难,不能满足大规模产业化的要求。在CIGS薄膜太阳能电池产业化进程中,克服其层间的附着力差,制备符合化学计量比具有黄铜矿结构的多晶薄膜吸收层是必须解决的两个最重要的工艺技术。本论文主要研究一种工艺简单、可控、适合产业化需要的技术工艺,即溅射制备合金预制膜后硒化的制备方法。研究采用的溅射系统,是本中心自行设计研制的三靶共溅设备,阴极大小为3英寸,衬底基座可以旋转,以保证制备薄膜的均匀。首先,在碱石灰玻璃衬底上制备厚度约1微米的钼电极,在溅射过程中通过改变工作气压,使Mo电极具有类似层状结构,消除了内应力的影响。通过扫描电镜分析,薄膜表面具有鱼鳞状结构,从而增加了Mo电极和CIGS吸收层之间的接触面积。Mo电极和玻璃衬底之间,及其和CIGS吸收层之间的附着力得到显著提高。然后,在沉积有Mo电极的玻璃衬底上,通过共溅射的方法制备约700纳米厚度的Cu（InGa）预制层薄膜,靶材采用CuIn和CuGa合金靶。硒化采用低温和高温过程依次进行的2步方法,采用固态硒源,硒化室是一个半密封的石墨盒。通过在高温区保温30分钟,制备出了性能优异的CIGS吸收层薄膜,具有（112）晶面择优取向,显示明显的黄铜矿单一结构。薄膜表面平整,晶粒大小均匀、排列紧密,晶粒大小达到3到5微米。用化学水浴法,制备厚度约70纳米的CdS过渡层。分别采用醋酸镉和硫尿作为镉源和硫源。研究了ZnS薄膜的制备工艺,对无镉电池的制备做了初步探索。最后用射频磁控溅射的方法,研究了常温下制备透明导电材料IT0和ZnO的制备工艺,研究了溅射功率和溅射气压对薄膜性能的影响。所制备的透明导电薄膜在可见光谱范围内,透过率到达80%到90%,方块电阻达到15Ω/□以下。在CIGS薄膜太阳能中,作为上电极材料,具有广泛的应用前景。通过大量的实验,优化了背电极Mo、吸收层CIGS、过渡层CdS（ZnS）、本征氧化锌i-ZnO和搀杂氧化锌n-ZnO（或者ITO）的制备工艺。最后,制备出了结构为Glass/Mo/CIGS/CdS/i-ZnO/n-ZnO/A1的CIGS电池器件。对器件的性能做了测试分析,在没有减反射层的情况下,转化效率达到7.8%。该研究采用的CIGS薄膜太阳能电池的制备工艺简单、过程容易控制、设备和材料费用低,没有采用剧毒的气源,适合大规模产业化的要求,为以后进一步的研究开发做了技术储备。更多还原

【Abstract】 The Cu（InGa）Se₂（CIGS）-based polycrystalline solar cell is regarded as a promising future generation of solar energy devices due to its low cost,high conversion efficiency and prominent stability.The highest conversion efficiency about 19.9%of CIGS based solar cells have been produced using the multi-stage co-evaporation technique at National Renewable Energy Laboratory（NREL）.Despite the demonstration of high efficiency by the co-evaporation technique for small size cells,there still exists some big challenges about its commercial deployment due to film uniformity problems over large areas,the extremely high costs of high vacuum facilities the technique requires and low utilization rates of materials.Industrial applications need cost effective deposition techniques.The related fabrication technologies need to be investigated and optimized.In this dissertation,one simple,reliable and reproductive technology was developed for CIGS solar cells by selenization of sputtering alloy precursors.A home-made magnetron sputtering machine containing three 3-inch diameter targets and a rotatable substrate holder was used.Firstly,～l.0μm thick Mo layers were deposited by DC-magnetron sputter on Corning soda lime substrates.The residual stresses were minimized by using two-layer structure and changing the working pressure.Next,700nm-thick CuInGa precursors were deposited onto Mo-coated glass substrates by Co-sputtering with two CuIn and CuGa alloy targets.A reproducible and easily scalable two-step selenization process of CuIn layers was developed to form high quality CIGS absorbing layers. High-quality CIGS absorbers have been formed by selenization of CuInGa precursors in a partially closed graphite container using selenium pellets at 500℃for 30 mins. The deposited CIGS absorbers exhibited a single phase chalcopyrite structure with a preferential orientation in the（112）direction.These layers were uniform,and the crystals were densely packed with a grain size of about 3～5μm.Then about 70nm thick CdS buffer layers were prepared by chemical bath deposition using cadmium acetate as the cadmium ion source and thiourea as the sulphur source.The synthesis of ZnS buffer layer were also studied for CdS-free CIGS solar cells.Finally,Indium tin oxide（ITO）and Al-doped ZnO films were deposited at room temperature with no oxygen flow on glass substrates by RF magnetron sputtering.The effects of sputtering power and argon ambient pressure were investigated.The deposited TCO films show a high transparency between 80 and 90%in the visible spectrum and 15Ω/□sheet resistance.Those TCO films are suitable for application in CuInGaSe2 thin film solar cell as transparent conductive electrode layers.Mo back contact,CIGS absorber,CdS/ZnS and i-ZnO/n-ZnO（ITO）layers have been investigated systemically and optimized.The properties of the deposited films were analyzed using scanning electron microscopy（SEM）,X-ray energy dispersive （EDX）and X-ray diffraction（XRD）.CIGS solar cells with the structure of Glass/Mo/CIGS/CdS/i-ZnO/n-ZnO/Al were tested and analysed.Efficiencies of～7.8%have been achieved without antireflective films.The whole technology of CIGS cells is simple,economical,and without using of toxic gases.It could easily be scaled up or integrated into a commercial process.更多还原