Stacked monolithic multi-junction solar cell comprising a first subcell, a second subcell, a third subcell and at least one fourth subcell in the stated sequence following one another, wherein - the band gap beginning from the first subcell is larger from subcell to subcell in direction towards the fourth subcell, - each subcell (SC1, SC2, SC3, SC4) comprises an n-doped emitter and a p-doped base, - the emitter and the base of the first subcell each comprise germanium or consist of germanium, - all subcells (SC2, SC3, SC4) following the first subcell each comprise an element of the III and V main group of the periodic system, - a respective tunnel diode (TD1, TD2, TD3) with a p-n transition is arranged between each two subcells (SC1, SC2, SC3, SC4), - all subcells (SC2, SC3, SC4) following the first subcell are constructed to be lattice-matched to one another, - an n-doped semiconductor mirror comprising several doped semiconductor layers with refraction indices differing in alternation is arranged between the first subcell and the following second subcell, and an n-doped metamorphic buffer is arranged between the first subcell and the semiconductor mirror, characterised in that the metamorphic buffer comprises at least four step layers and at least one overshoot layer, and the doping of the layers of the n-doped metamorphic buffer lies below a value of 1 • 10 18 cm -3, and at least two of the layers of the metamorphic buffer have a doping less than 8 •10 17 cm -3, a tunnel diode is arranged between the second subcell and the semiconductor mirror so that the metamorphic buffer, the semiconductor mirror, the tunnel diode and the second subcell follow on the first subcell in the stated sequence. - the band gap beginning from the first subcell is larger from subcell to subcell in direction towards the fourth subcell, - each subcell (SC1, SC2, SC3, SC4) comprises an n-doped emitter and a p-doped base, - the emitter and the base of the first subcell each comprise germanium or consist of germanium, - all subcells (SC2, SC3, SC4) following the first subcell each comprise an element of the III and V main group of the periodic system, - a respective tunnel diode (TD1, TD2, TD3) with a p-n transition is arranged between each two subcells (SC1, SC2, SC3, SC4), - all subcells (SC2, SC3, SC4) following the first subcell are constructed to be lattice-matched to one another, - an n-doped semiconductor mirror comprising several doped semiconductor layers with refraction indices differing in alternation is arranged between the first subcell and the following second subcell, and an n-doped metamorphic buffer is arranged between the first subcell and the semiconductor mirror, characterised in that the metamorphic buffer comprises at least four step layers and at least one overshoot layer, and the doping of the layers of the n-doped metamorphic buffer lies below a value of 1 • 10 18 cm -3, and at least two of the layers of the metamorphic buffer have a doping less than 8 •10 17 cm -3, a tunnel diode is arranged between the second subcell and the semiconductor mirror so that the metamorphic buffer, the semiconductor mirror, the tunnel diode and the second subcell follow on the first subcell in the stated sequence. an n-doped metamorphic buffer is arranged between the first subcell and the semiconductor mirror, characterised in that the metamorphic buffer comprises at least four step layers and at least one overshoot layer, and the doping of the layers of the n-doped metamorphic buffer lies below a value of 1 • 10 18 cm -3, and at least two of the layers of the metamorphic buffer have a doping less than 8 •10 17 cm -3, a tunnel diode is arranged between the second subcell and the semiconductor mirror so that the metamorphic buffer, the semiconductor mirror, the tunnel diode and the second subcell follow on the first subcell in the stated sequence.