非晶硅/晶体硅异质结太阳电池高效减反射ITO纳米线电极研究

The dense indium tin oxide (ITO) nanowire which has efficient antireflection, low absorption, high electrical conductivity will be fabricated on textured silicon substrate at low temperature by oblique angle magnetron sputtering. It has been employed as transparent conductive electrode of amorphous/crystalline silicon heterojunction solar cells. In addition, it plays the role of the efficient antireflection. The short circuit current of amorphous/crystalline silicon heterojunction solar cells with ITO nanowire electrode increases compared to conventional cells. Compared to light trapping of silicon nanostructure, the high open-circuit voltage will be kept because of absence of defect state on silicon surface. ITO are fabricated at selected different deposition parameters on the textured silicon substrate according to the theoretical simulation analysis results. Microstructures, optoelectronic of them and interface properties with doped silicon thin film layer will be studied with several techniques. In situ optical emission spectroscopy technology is used to study the materials deposition process. The relationship of macroscopic parameters-plasma-ITO morphology and performance will be determined. By the investigation of this project, it is expected to reveal the growth mechanism of ITO nanowire fabricated at low temperature by oblique angle magnetron sputtering. The method and mechanism to decrease self absorption of ITO nanowire will be obtained. The efficient antireflection mechanism of ITO nanowire can be illuminated clearly.The expected achievements can provide theoretical guidance for the practical fabrication process of the preparation of low cost and high efficiency silicon solar cells.

本项目拟采用倾斜角磁控溅射，在制绒硅衬底上低温无金属催化剂制备密集的、高减反射、低吸收、高电导性的氧化铟锡(ITO)纳米线材料，将其用作非晶硅/晶体硅异质结太阳电池的透明导电电极，起到高效减反射作用，提升电池短路电流密度的同时，相比于硅纳米结构陷光，还可以避免硅衬底表面缺陷态的增加，保持电池的高开路电压特性。重点结合理论模拟结果，通过调节沉积参数，在织绒的晶体硅衬底表面制备不同性能的ITO纳米线材料，采用各种表征手段对其光学、电学及与硅薄膜掺杂层界面接触等特性进行研究，结合光发射谱对溅射过程中的等离子体状态进行诊断，确定宏观参数-等离子体状态-ITO纳米材料形貌和性能之间的关系。通过本项目的研究，揭示低温倾斜角磁控溅射制备ITO纳米材料的生长机制，获得降低其自吸收的方法与机理,探明其高效减反射的作用机理，从而对具体的低成本、高效太阳电池制备工艺提供理论指导。

非晶硅/晶体硅异质结太阳电池(HIT)透明导电膜(TCO)自身光吸收对电池输出电流没有贡献，却造成电池的短波和长波损失。本项目采用倾斜角磁控溅射，在制绒硅衬底上低温无金属催化剂成功制备密集的、高减反射、低吸收、高电导性的氧化铟锡(ITO)纳米薄膜。重点结合理论模拟结果，通过调节倾斜角等沉积参数，制备不同性能的ITO纳米材料，采用各种表征手段对其光学、电学及与硅薄膜掺杂层界面接触等特性进行研究，借助光发射谱原位诊断技术，从微观上揭示低温倾斜角磁控溅射制备ITO纳米材料的生长机制。倾斜角较大程度影响了ITO纳米薄膜的形貌，随着倾斜角从22度增大到87度，薄膜结构由纳米线过渡到纳米柱，其晶粒尺寸、粗糙度和折射率逐渐增大，但对透过率影响程度较小。采用AFORS-HET软件模拟得到：对于TCO/a-Si:H(p)/c-Si(n)结构，发射极掺杂浓度约为1×1020cm-3，TCO功函数不小于5.2eV，电池的性能较好。最终将其沉积在织绒的硅衬底表面，相比常规ITO透明电极，反射率降低1.8%，用作HIT电池的透明导电电极，采用线传输法测试银栅线和ITO纳米电极之间的接触电阻在1.0-1.5Ω之间，电池短路电流密度提高1.39mA/cm2，效率改善1.22%。对晶硅太阳电池而言，效率每提升1%，成本可下降7%，若将纳米电极成功应用于太阳电池，对于降低成本的效果相当显著。通过本项目的研究，揭示了低温倾斜角磁控溅射制备ITO纳米材料的生长机制，探明了其高效减反射的作用机理，从而对低成本、高效太阳电池制备的具体工艺提供理论指导。