Cost-effective cleaning solutions based on H 2 O/NH 3 /H 2 O 2 mixtures for ALD Al 2 O 3 passivated IBC c-Si solar cells

In this work we study cost-effective cleaning solutions applied to interdigitated back-contacted solar cells (IBC), which are passivated by means of atomic layer deposited Al 2 O 3 films. The cleaning baths must guarantee very clean surfaces as well as relatively low etching Al 2 O 3 rates to avoid excessive undercutting at the edges of strip-like regions. We compare the standard high-cost cleaning procedure used in the microelectronic industry (RCA1/2) with simpler cleaning baths based on H 2 O/NH 3 /H 2 O 2 mixtures considering different temperatures. The best option is the RCA1/2 sequence yielding surface recombination velocities below 4 cm/s but with a total Al 2 O 3 etch around 500 nm after the cleaning stage. Nevertheless very simple and less aggressive cleaning baths performed at only 45 °C obtain a relatively good surface passivation quality, achieving S eff values of 20 ± 5 cm/s reducing the under etch to only 80 nm.