Efficiency improvement of Si quantum dot solar cells by activation with boron implantation

•A Si QD heterojunction solar cell by the ion implantation process was successfully fabricated.•The activation effect of a B-doped Si QD layer created by a co-deposition process was compared with that by B implantation process.•The power conversion efficiency of a Si QD solar cell increased from 13.17% to 13.92% by fabrication with ion implantation. 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 mV to 529.64 mV in the Si QD solar cell created with the ion implantation of B.