Surface Passivation for High Efficiency Crystalline Silicon Solar Cells

为了研究高效晶体硅太阳能电池的钝化效果，在单晶硅和多晶硅衬底上沉积单层或双层氮化硅（SiNx: H）薄膜和非晶硅（a-Si: H）薄膜。对有效载流子寿命和热退火效果进行了评价。得到了以下结果：富Si膜的钝化效果比富N膜的钝化效果更明显。热退火对有效寿命的影响：SiNx: H薄膜的有效寿命受热退火温度和持续时间的影响很大。FTIR结果证实，H原子迁移改变了Si-H键和N-H键的密度，这种行为与钝化效应有关。SiNx: H/ SiNx: H双层膜的钝化效果：通过不同折射率的SiNx: H膜的组合，有效寿命得到了较大的提高。此外，还可以控制表面反射性能。SiNx: H/ a-Si: H双镀层的钝化效果：在250C低温下沉积了SiNx: H/ a-Si: H双镀层。发现这些层对有效载流子寿命有极高的改善作用。此外，热退火还提高了材料的有效寿命。a-Si:H单层膜的钝化效果：在250℃下沉积的a-Si:H单层膜，在400-500℃下进行热退火，有效寿命得到极大提高。太阳能电池钝化膜的评价：太阳能电池实际上是在我们的实验室制造的。考察了电池表面的SiNx: H膜和电池BSF层的a-Si: H膜的作用。验证了对转换效率的改进效果。

To investigate the passivation effects for high efficiency crystalline silicon solar cells, single layers or double layers of silicon nitride (SiNx : H) film and amorphous silicon (a-Si : H) film were deposited on mono-crystalline and multi-crystalline silicon substrates. The effective carrier lifetime and the thermal annealing effect were evaluated. The following results were obtained.1. Passivation effects of SiNx : H films : Si rich films showed larger improvement of effective lifetime than N rich films.2. Thermal annealing effect for the effective lifetime : The effective lifetimes in SiNx : H films were largely changed by temperature and duration of thermal annealing. From the results of FTIR, it was confirmed that the densities of Si-H and N-H bonds are changed by H atoms migration and this behavior is related to the passivation effect.3. Passivation effects of SiNx : H/ SiNx : H double layers : By combination of SiNx : H films with different refractive indices, the effective lifetimes were more improved. Also it is possible to control the surface reflective property.4. Passivation effects of SiNx : H/ a-Si : H double layers: SiNx : H/ a-Si : H double layers were deposited at low temperature of 250C. These layers were found to show extremely high improvement effect for the effective carrier lifetimes. Moreover the effective lifetimes were increased by thermal annealing.5. Passivation effects of a-Si:H single layers: In a-Si:H single layers deposited at 250 C, the effective lifetimes were extremely improved by thermal annealing at 400-500 C.6. Evaluation of passivation films for solar cells : The solar cells were actually made in our laboratory. The effects of SiNx : H film on the surface of the cell and a-Si : H film on the BSF layer of the cell were evaluated. As a result, improvement effects for conversion efficiency were verified.