Tunneling or Pinholes: Understanding the Transport Mechanisms in SiOx Based Passivated Contacts for High-Efficiency Silicon Solar Cells

We have compared the temperature dependence of the poly-Si/SiOx/c-Si contact performance for 1.5 and 2.2 nm thick SiOx. The optimum annealing temperature for these two is different, likely due to the SiOx influencing the extent of dopant diffusion into c-Si. At 1050°C, while a contact with 1.5 nm SiOx significantly breaks up, the one with 2.2 nm SiOx develops pinholes. Using scanning Kelvin probe microscopy, we demonstrate that there is enhanced dopant diffusion through these pinholes. Finally, using electron-beam induced current measurements, we show that pinholes affect the local passivation quality of the c-Si wafer surface.