Recent Progress in Understanding the Properties of the Amorphous Silicon/Crystalline Silicon Interface

摘要

The authors review experimental and modeling approaches developed at GeePs to have a better knowledge and understanding of the interface between hydrogenated amorphous silicon (aSi:H) and crystalline silicon (cSi) in heterojunction solar cells. The authors emphasize the existence of a strong inversion layer at the cSi surface for both (n) aSi:H/(p) cSi and (p) aSi:H/(n) cSi heterojunctions. Conductive probe atomic force microscopy reveals the existence of a conductive channel at the cSi surface. The analysis of complementary lateral planar conductance and capacitance measurements allows for a better description of the band diagram in both types of heterojunctions especially through the determination of band offset values. Furthermore, the passivation properties of the (i) aSi:H buffer layer are studied by modeling the volume defects in aSi:H with the defectpool model. In particular, the DOS in the very thin (i) aSi:H layers is much larger than in bulk (i) aSi:H because the Fermi level position favors defect creation. Surface defects in cSi at the aSi:H/cSi interface are then quantified and the general trends of effective lifetime measurements with the (i) aSi:H layer thickness can be explained, notably the increase of the effective lifetime in cSi with increasing the (i) aSi:H buffer thickness.