Ultra-high quality surface passivation of crystalline silicon wafers in large area parallel plate reactor at 40 MHz
We use a new in-house, large area and automated deposition system: the usable deposition area is 410 × 520 mm with RF-frequency of 40 MHz. We deposit intrinsic a-Si:H layer on flat p-type or n-type c-Si wafers after performing an HF dip. The overall recombination of these double-side passivated c-Si wafers is measured with an effective lifetime measurement set-up. We pay particular attention to the uniformity of the passivation obtained on the whole deposition area. We point out a major role of hydrogen dilution on quality of c-Si passivation. Excellent uniformity is obtained on the whole area with implied open-circuit voltages (Voc) in a ± 1.5% range. We achieve excellent passivation with overall lifetimes approaching 7 ms (at Δn ≈ 4.5·1014 cm− 3) resulting in implied Voc of 708 mV on p-type c-Si; and lifetimes superior to 4.7 ms resulting in implied Voc of 726 mV on n-type c-Si (Seff less than 2 cm/s for both). These results open the way to very high efficiency heterojunction solar cell fabrication in large area reactors.