非晶硅/晶体硅异质结太阳电池载流子输运机制与界面钝化特性研究

Amorphous/crystalline silicon heterojunction (SHJ) solar cell is recognized as one kind of low cost and high efficiency solar cell in the world. However, it is difficult for most institutes and companies to obtain high efficiency currently, except for Sanyo, which indicates that SHJ solar cell has still not been understood clearly by the researchers. So, the proposed project here will investigate the carrier transport mechanisms of the SHJ solar cell carefully and make the dominant mechanism clear for high efficiency solar cell by temperature and illumination intensity dependent I-V curve testing. The energy band structure of the SHJ interface will be improved by performing doped hydrogen plasma pretreatment on the silicon substrate. Further, the plasma state of the amorphous silicon deposition will be in-situ monitored by plasma optical emission spectroscopy(OES). The plasma state dependence of the passivation effect of the amorphous silicon layer will be analyzed systematically. It is expected to reveal the passivation mechanism based on the plasma state. By the investigation of this project, the mechanism for SHJ solar cell to obtain high efficiency can be illuminated clearly and the expected achievements can provide theoritical guidance for the practical fabrication process of the SHJ solar cell.

非晶硅/晶体硅异质结(SHJ)太阳电池是国际上公认的一种低成本高效率的太阳电池，但除日本Sanyo公司外，世界各大研究机构或公司都难以获得高效率，说明人们对它的认识仍然不甚清楚。因而，本项目拟深入研究SHJ太阳电池的载流子输运机制，通过变温变光强I-V曲线测试，分析判明在高效电池中占主导地位的载流子输运类型；并通过对硅衬底进行掺杂氢等离子体预处理的方式来调节改善SHJ界面的能带结构；进而采用等离子体辉光发射谱(OES)对沉积非晶硅层的等离子体状态进行即时监测，分析确定非晶硅层钝化性能与等离子体状态间的依赖关系，从等离子体的角度揭示非晶硅层界面钝化的内在机制。通过本项目的研究，能够探明SHJ太阳电池的高效机理，从而对具体太阳电池制备工艺提供理论指导。

非晶硅/晶体硅异质结(SHJ)太阳电池被国际上公认为是高效硅太阳电池的“明智选择”，但各大研究机构或公司都难以获得像日本松下公司那样的高效率，说明人们对它的认识仍然不甚清楚。本项目深入研究了SHJ太阳电池的载流子输运机制，确定了高效非晶硅/晶体硅异质结太阳电池在工作电压条件下占主导的载流子输运机制是扩散机制，并给出了高效SHJ太阳电池的优化结构设计。开发了异质结界面实现高性能钝化的有效方法，简化的RCA清洗工艺结合金字塔绒面表面圆滑处理加上高性能非晶硅钝化层沉积是硅衬底获得长有效少子寿命的保证。确立了非晶硅层钝化性能与等离子体状态间的联系，等离子体光发射谱(OES)中的SiH/Hα发光峰比值可以作为监控非晶硅钝化性能的重要指标，相对较大的SiH/Hα发光峰比值可以带来好的钝化效果。进而确定了非晶硅内部微结构和成键状况与界面钝化特性之间的关系，富含SiH键的微结构较致密的非晶硅材料是获得优异界面钝化性能的首选。在所获得的理论研究成果基础上，通过具体优化制备工艺，使非晶硅钝化后的Cz硅衬底的有效少子寿命达到了9 ms以上，156 mm×156 mm的准方大面积SHJ太阳电池的开路电压达到了732 mV，效率达到了22.25%。本项目所获理论研究成果可为实际制备高性能SHJ太阳电池提供科学指导。所开发的实际电池制备技术也达到了国际先进水平，可为实现SHJ太阳电池的规模化生产打下良好基础。