Low-Temperature, PECVD-Grown Nanocrystalline Silicon Oxide as a Metal Diffusion Barrier for Silicon Heterojunction Solar Cells

Beyond its role as a transparent conducting electrode, the indium tin oxide (ITO) layer in silicon heterojunction (SHJ) solar cells also prevents metal diffusion upon annealing. However, the limited supply and high cost of indium remain a major challenge. Herein, we demonstrate that n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiO_x:H) can serve as both a doped layer and an effective barrier against metal diffusion. SHJ cells with n-nc-SiO_x:H maintained a stable V_OC of 723 mV while fully suppressing Al diffusion during annealing, unlike conventional n-a-Si:H and n-nc-Si:H. In architectures not requiring a transparent lateral transport layer, n-nc-SiO_x:H layers enable ITO-free device designs.