Intermediate Layer Development for Laser-Crystallized Thin-Film Silicon Solar Cells on Glass

The intermediate layer (IL) between the glass and silicon plays an important role in laser-crystallized thin-film silicon solar cells. SiO
_X
, SiN
_X
, and SiC
_X
deposited by RF sputtering or plasma-enhanced chemical vapor deposition, either as single layers or in stacks, have been tested as ILs with regard to silicon wettability and silicon crystal quality and the effect of hydrogen passivation. SiC
_X
is the best wetting layer, allowing a larger laser crystallization process window than SiO
_X
or SiN
_X
. SiN
_X
layers are limited by pinholing, which increases in severity with laser fluence. SiO
_X
ILs result in lower silicon grain-boundary density compared with SiC
_x
-based layers and to SiN
_X
-based layers. Hydrogen passivation of laser-crystallized silicon on single layer SiO
_X
has no impact on V
_OC
, while an improvement of around 60 mV is found for samples on SiO
_x
/SiN
_x
/SiO
_x
stacks. Diffusion of dopants from the IL are found to create a uniformly doped absorber with no evidence of a front-surface field.