Structural, hydrogen bonding andin situstudies of the effect of hydrogen dilution on the passivation by amorphous silicon of n-type crystalline (1 0 0) silicon surfaces

Improved Surface Passivation by Wet Texturing, Ozone‐Based Cleaning, and Plasma‐Enhanced Chemical Vapor Deposition Processes for High‐Efficiency Silicon Heterojunction Solar Cells

“…The lifetime curves show clearly that when using the highly H 2 ‐diluted i‐layer in direct contact with the wafer surface, the passivation is detrimentally affected; lifetime decreases by more than 6 ms at an injection level of 10 15 cm −3 , compared with the sample with the low dilution layer at the interface. This indicates that the layer with R = 23 might induce localized epitaxial growth between the c‐Si/a‐Si interface, as already observed by several groups with PECVD intrinsic hydrogenated layers deposited with R > 5 . As reported in the literature, increasing the hydrogen dilution of the a‐Si plays a crucial role in passivating the dangling bonds, but an excessive H 2 dilution promotes crystalline (epitaxial) growth of the a‐Si on the c‐Si wafer surface .…”

“…This indicates that the layer with R ¼ 23 might induce localized epitaxial growth between the c-Si/a-Si interface, as already observed by several groups with PECVD intrinsic hydrogenated layers deposited with R > 5. [22,23] As reported in the literature, increasing the hydrogen dilution of the a-Si plays a crucial role in passivating the dangling bonds, but an excessive H 2 dilution promotes crystalline (epitaxial) growth of the a-Si on the c-Si wafer surface. [23,24] Thus, using the high H 2 dilution material for layers i 2 and i 3 on top of an i 1 with low H 2 dilution provides the best passivation of all investigated combinations correlating to the higher H 2 content in the bulk of the passivating structure avoiding the epitaxial growth on the c-Si wafer surface thanks to the first i-layer, i 1 , which is deep in the amorphous regime, low dilution, and high deposition rate.…”

“…[22,23] As reported in the literature, increasing the hydrogen dilution of the a-Si plays a crucial role in passivating the dangling bonds, but an excessive H 2 dilution promotes crystalline (epitaxial) growth of the a-Si on the c-Si wafer surface. [23,24] Thus, using the high H 2 dilution material for layers i 2 and i 3 on top of an i 1 with low H 2 dilution provides the best passivation of all investigated combinations correlating to the higher H 2 content in the bulk of the passivating structure avoiding the epitaxial growth on the c-Si wafer surface thanks to the first i-layer, i 1 , which is deep in the amorphous regime, low dilution, and high deposition rate. As mentioned before, after each i-layer from the stack, a short HPT is done to treat the underlying layers, leading to a lower defect density layer that improved the resulting passivation of the silicon wafer.…”

Limitations of high pressure sputtering for amorphous silicon deposition

“…This band is related with good passivation of c-Si wafers with a-Si:H, because, as it is well known, when the dominant bonds are Si-H 2 , a higher the density of microvoids and defects is present in the film, thus reducing the film quality [22].…”

Determination of Defect Densities in Thin (i) a‐Si:H Used as the Passivation Layer in a‐Si:H/c‐Si Heterojunction Solar Cells from Static Planar Conductance Measurements

“…However, the defect density in the buffer (i) a‐Si:H layer and the (i) a‐Si:H/c‐Si interface state density could never be directly measured in solar cell structures. The quality of the interface is assessed at the cell level from the photovoltaic performance of the solar cell or at an earlier step of cell fabrication from the effective lifetime on cell precursors consisting of c‐Si wafers with the a‐Si:H layers deposited on both faces . Both the photovoltaic performance and the effective lifetime are related to the dynamics and recombination of photogenerated carriers, which do not depend only on the density of defects but also on their degree of occupation and on their capture cross sections.…”