传统铝背表面场（Al-BSF）已不能满足高效率晶体硅太阳电池（尤其是薄晶体硅电池）背结构的技术要求。传统Al-BSF的技术缺点包括：（1）背面复合速度偏高；（2）背面内反射率较低；（3）烧结后的铝背电极因与晶体硅热膨胀系数不匹配导致薄电池片的严重翘曲，将引起电池破片率的显著升高。传统Al-BSF的这些技术缺点可以通过背钝化、局域BSF（LBSF）、局域背电极接触技术来解决。现有研究表明硼掺杂LBSF（B-LBSF）是该类背钝化晶体硅太阳电池的核心结构，使高性能局域背电极接触成为可能。本项目针对现有B-LBSF制备工艺的技术弱点提出了一条简捷可靠的技术路线和研究思路，硼掺杂源和背钝化膜的制备将采用PECVD技术一步完成，借助脉冲激光技术实现B-LBSF的可控硼掺杂，获得性能优异的B-LBSF。我们已开展了制备B-LBSF的前期工作并得到了较理想的初步结果，为本项目的顺利实施打下了扎实的基础。

The traditional aluminum back surface field (Al-BSF) does not meet the requirements of back surface structures of high efficiency crystalline silicon solar cells, especially for the thinner silicon solar cells. The limitations of the traditional Al-BSF technology include: (1) the Al-BSF cell still has relatively high back surface recombination velocity; (2) the internal back surface optical reflection of the Al-BSF cell is low; and (3) the warping problem becomes much more serious for thinner silicon solar cells, and the cell breakage rate will become much higher. These limitations for Al-BSF can be eliminated by using the rear passivation, local BSF (LBSF), and local back contact technology. It has been shown that boron doped LBSF (B-LBSF) is crucial for such type of cells. This proposed research project intends to develop a new approach for tailoring the boron doping process in the B-LBSF, and in the meantime eliminate the technical drawbacks and process complexity associated with the present technologies for fabricating B-LBSF. The B doping source and the passivating layers are to deposited in one step using a PECVD system. We will employ a pulsed laser to implement boron doping within the B-LBSF in a highly controlled manner. The B-LBSF is expected to have outstanding electrical properties. We have conducted some preliminary research work for preparing B-LBSF and obtained some initial experimental results. This will be very beneficial for this proposed project.