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.