Plasma immersion ion implantation of hydrogen with low kinetic energy (1 kV) was used to passivate solar cells to increase efficiency. The plasma sheath encloses the wafer cell and hydrogen ions can be implanted into the entire cell surface. The passivation is omnidirectional, and is particularly effective at the edge surface of the solar cell. The large diffusion length of carriers in Si solar cell is susceptible to edge defects, since the photo-generated carriers can diffuse to the edge surfaces and recombine to degrade the efficiency. Moreover, the dielectric/silicon interface can be effectively passivated due to energetic hydrogen from plasma. For small-area cell, an increase in relative efficiency of 4.4% was obtained after a 90 s plasma immersion ion implantation treatment. Both the external quantum efficiency for 400-500 nm wavelength photons and photoluminescence intensity increase by similar to 6% and similar to 29% relatively. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610346] All rights reserved.