The
application of dopant-free carrier-selective contacts has great
advantages in simplifying the fabrication process and has potential
to achieve higher power conversion efficiency (PCE) for crystalline
silicon (c-Si) solar cells over traditional highly doped ones. In
this paper, we demonstrate a material, GdF3, which shows
a low work function and forms a low contact resistivity (ρc) Ohmic contact with lightly doped n-type c-Si (n-Si). Besides,
the low ρc can be easily repeated and show good stability
in an ambient atmosphere within a wide thickness variation (1.4–5.6
nm) for the GdF3/Al stack. Furthermore, the diffusion of
Al into the GdF3 layer is observed from the interface image
and elemental distribution, which explain its high thickness tolerance.
The dopant-free GdF3/Al electron-selective contact is applied
to n-Si solar cells with partial rear contact architectures, achieving
a champion PCE of 20.71%, demonstrating its great potential for mass
production of optical–electrical devices.