© 2019 Abdullah Uzum et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Aluminum acetylacetonate-based AlO x thin films were introduced as a low-cost, high-quality passivation layers for crystalline silicon solar cells. Films were formed by a spin coating method on p-type silicon substrates at 450 ° C in ambient air, O 2 , or water vapor (H 2 O/O 2 ) for 15 or 120 min. XPS analysis confirms the AlO x formation and reveals a high intensity of interfacial SiO x at the AlO x /Si interface of processed wafers. Ambient H 2 O/O 2 was found to be more beneficial for the activation of introduced AlO x passivation films which offers high lifetime improvements with a low thermal budget. Carrier lifetime measurements provides that symmetrically coated wafers reach 119.3 μs and 248.3 μs after annealing in ambient H 2 O/O 2 for 15 min and 120 min, respectively.