High Quality Aluminum Oxide Passivation Layer for Crystalline Silicon Solar Cells Deposited by Parallel-Plate Plasma-Enhanced Chemical Vapor Deposition

We investigated hydrogenated aluminum oxide (a-Al 1- x O x :H) as a high quality rear surface passivation layer of crystalline silicon solar cells. The a-Al 1- x O x :H films were deposited by plasma-enhanced chemical vapor deposition (PECVD) using a mixture of trimethylaluminum (TMA), carbon dioxide (CO 2 ), and hydrogen (H 2 ) at a low substrate temperature of about 200 °C. The ratio of CO 2 to TMA during deposition and thermal annealing after the film deposition are the key factors in achieving high quality passivation. A 28-nm-thick a-Al 1- x O x :H film deposited by PECVD showed a low surface recombination velocity of about 10 cm/s.