Large Area 21.6% Efficiency Front Junction N-type Cell with Screen Printed Tunnel Oxide Passivated Poly-Si Rear Contact

We report on the implementation of screen printed carrier-selective tunnel oxide passivated poly-Si rear contact for high-efficiency front junction crystalline Si solar cells. Using a 15Å thick tunnel oxide grown in nitric acid at 100°C and capped with 100nm LPCVD grown n
⁺
poly-Si, we were able to achieve excellent rear contact passivation even after the formation of screen printed contacts. The saturation current density on the rear side (J
_0b'
) without metal was 1.7 fA/cm
²
. After firing the screen printed Ag contacts through SiN cap on poly-Si, with 9% metal coverage, J
_0b'
increased to only ~5 fA/cm
²
. An ion-implanted 180 Ω/□ boron doped homogeneous emitter was used on the front. This resulted in large area (239 cm
²
) 21.6% cells on industrial grade n-type CZ Si wafer. Smaller area 100 cm
²
cells gave 22% efficiency.