Solar cell unit comprising - a semiconductor body, which is constructed as a solar cell, with a receiving surface, - a carrier with an upper side and a lower side, wherein the semiconductor body is electrically connected with and mechanically positively coupled to the upper side of the carrier, and - a transparent secondary optical element mechanically positively connected with the receiving surface, wherein the optical element has a surface, wherein a part of the surface is formed as a substantially convex receiving surface and sunlight incident on the convex surface is focused by means of the convex receiving surface of the optical element, wherein the convex receiving surface of the optical element is surrounded by a shoulder-shaped step, wherein the shoulder-shaped step has a first edge surface and a second edge surface, and wherein the normal vector of the first edge surface and the normal vector of the second edge surface are formed to be substantially parallel to the optical axis of the optical element and the normal vectors point against the direction from the incident sunlight, and in the case of the shoulder-shaped step a first adjusting mark (60; 70) is arranged on the first edge surface and a second adjusting mark (60; 70) is arranged on the second edge surface so as to position and align the optical element with respect to the receiving surface of the solar cell by means of the two adjusting marks (60; 70), wherein the first adjusting mark (60; 70) is spaced from the second adjusting mark (60; 70) so as to conduct sunlight incident on the optical element to the receiving surface of the solar cell. - a semiconductor body, which is constructed as a solar cell, with a receiving surface, - a carrier with an upper side and a lower side, wherein the semiconductor body is electrically connected with and mechanically positively coupled to the upper side of the carrier, and - a transparent secondary optical element mechanically positively connected with the receiving surface, wherein the optical element has a surface, wherein a part of the surface is formed as a substantially convex receiving surface and sunlight incident on the convex surface is focused by means of the convex receiving surface of the optical element, wherein the convex receiving surface of the optical element is surrounded by a shoulder-shaped step, wherein the shoulder-shaped step has a first edge surface and a second edge surface, and wherein the normal vector of the first edge surface and the normal vector of the second edge surface are formed to be substantially parallel to the optical axis of the optical element and the normal vectors point against the direction from the incident sunlight, and in the case of the shoulder-shaped step a first adjusting mark (60; 70) is arranged on the first edge surface and a second adjusting mark (60; 70) is arranged on the second edge surface so as to position and align the optical element with respect to the receiving surface of the solar cell by means of the two adjusting marks (60; 70), wherein the first adjusting mark (60; 70) is spaced from the second adjusting mark (60; 70) so as to conduct sunlight incident on the optical element to the receiving surface of the solar cell.