We are presenting a solar cell consisting of electron-doped graphene (n-G)/holes-doped silicon (p-Si) Schottky junction, which provides a very high power conversion efficiency (PCE). The high PCE of our solar cell is caused by its high Schottky barrier height, which gives a very low value for the saturated reverse current (I0), and consequently, occurs a very low value of the current flowing through the forward-biased Schottky junction (value tending to zero). Therefore, as all photogenerated current goes to the external circuit, the solar cell PCE, we are presenting is very high, which exceeds the Shockley–Quiesser limit. It is noteworthy that the n-G/p-Si solar cells with resistance series Rs = 17.52 Ω, and Rs = 10.00 Ω presented PCE values ≈ 22.55%, and ≈ 39.51%, respectively. Since there is no current going through the Schottky junction, that n-G/p-Si solar cell operates similarly to an electrochemical generator. To get the characteristic parameters of our solar cell, we used an analytical/numerical methodology.