The invention discloses a high-quality four-junction space
solar cell and a preparation method thereof. The high-quality four-junction space
solar cell comprises a Ge substrate, and a Ge sub-
cell, a GaInP nucleating layer, a GaInAs buffer layer, a first tunneling junction, a component gradient buffer layer, a DBR reflection layer, a GaInAs sub-
cell, a second tunneling junction, an AlGaInAs sub-
cell, a third tunneling junction and an AlGaInP sub-cell are sequentially arranged on the Ge substrate. Depletion
layers are formed between base regions and emitter regions of the AlGaInAs sub-cell and the AlGaInP sub-cell, the base regions and the emitter regions are of
band gap gradual change structures, and the
band gap gradual change structures are introduced into the Al-containing sub-cell, so that the
material quality of the depletion
layers is improved, the minority carrier
recombination rate of a main
photon-generated carrier generation region is reduced, and the
photon-generated carriercollection efficiency is improved. The gradual change
band gap has the effect of an auxiliary back field, so that
photon-generated carriers far away from the depletion layer drift towards the depletion layer, the Al component far away from the depletion layer enables the effective band gap of the Al-containing sub-cell to be wider, and higher open-circuit
voltage can be obtained.