Study of the interface in n~+ μc-Si/p-type c-Si heterojunctions: role of the fluorine chemistry in the interface passivation

摘要

Investigation of n-p heterojunction solar cells obtained by depositing a n-type thin silicon films either amorphous or microcrystalline on p-type c-Si is carried out. The study is focused on the improvement of the c-Si surface and emitter layer/c-Si substrate interface. The peculiarity is the use of SiF_4-based plasmas for the in situ dry cleaning and passivation of the c-Si surface and for the PECVD deposition of the emitter layer that can be either amorphous (a-Si:H,F) or microcrystalline (μc-Si). The use of SiF_4 instead of the conventional SiH_4 results in a lower hydrogen content in the film and in a reduction of the interaction of the c-Si surface with hydrogen atoms. Furthermore, the dependence of the heteroj unction solar cell photovoltaic parameters on the insertion of an intrinsic buffer layer between the n-type thin silicon layer and the p-type c-Si substrate is discussed.