The activation of Si quantum dots (QDs) in general Si QD heterojunction solar cells fabricated by the co-deposition of Si and B is typically not effective, as a high concentration of B is required for effective activation. In order to address this issue, B atoms were injected by ion implantation after the formation of Si QDs in a SiO2 matrix. A Si QD solar cell was successfully realized when a Si QD layer was activated by the implantation of B ions followed by an annealing step. As a result, the power conversion efficiency of a Si QD solar cell realized by the ion implantation of B increased from 13.17% to 13.92%. The open-circuit voltage also increased from 523.03 my to 529.64 mV in the Si QD solar cell created with the ion implantation of B.