Silicon (Si) quantum dot (QD) materials have been proposed for all-Silicon tandem solar cells. In this study, for the first time, high efficiency solar cells consisting of a sub-10-nm highly ordered and dense 2-dimensional (2D) array (one layer) of Si nanodisks (Si-ND) with a silicon carbide (SiC) interlayer have been fabricated. These Si-NDs were fabricated with an original top-down process involving a 2D-array bio-template etching mask made of Listeria-Dps (Li-Dps) with a 4.5-nm-diameter iron oxide core and damage-free neutral beam etching (Si-ND diameter: 6.4 nm). The Si-ND 2D array with a SiC interlayer had an extremely high optical absorption coefficient and high carrier transport due to the formation of a wide mini-band between the Si-NDs through the SiC interlayer. As a result, an open-circuit voltage of 0.556 V, short-circuit current of 31.3 mA/cm2, fill factor of 72%, and conversion efficiency of 12.6% were accomplished just by inserting one-layer Si-NDs in solar cells.