SURFACE PASSIVATION QUALITY AND STRUCTURE OF THIN Si:H LAYERS ON N-TYPE CRYSTALLINE Si (100) AND (111) WAFERS

Silicon surface passivation of hydrogenated silicon (Si:H) thin films deposited by radio frequency (RF) and direct current (DC) plasma process was investigated by measuring effective minority carrier lifetime (τeff) on Si (100) and (111) wafers and correlated with the silicon heterojunction (SHJ) cell performances. Apparently the higher ion bombardment in DC compared to RF plasma during growth of amorphous Si:H layer does not deteriorate Si surface passivation properties. Microstructural defects associated with SiH2 bonding have only a weak influence on τeff. However, any epitaxial growth or presence of crystallinity in the Si:H i-layer severely degrades passivation properties and SHJ cell performance. Excellent surface passivation (τeff > 1 msec) and high efficiency SHJ cells are obtained by both RF and DC plasma deposited intrinsic a-Si:H buffer layer. High efficiency (>18%) with open circuit voltage (VOC) of 694 mV was achieved on n-type textured Cz wafer using DC plasma process.