Three-junction solar cell and preparation method thereof

The invention relates to the technical field of solar cells, particularly relates to a three-junction solar cell and a preparation method thereof and aims to solve problems that in the prior art, eachsub-cell is low in current density matching performance, poor in epitaxial crystal quality, low in yield and difficult to produce in batches. The solar cell comprises a GaAs sub-cell and a first epitaxial layer located on one side of the GaAs sub-cell, and a second epitaxial layer which is positioned on the other side of the GaAs sub-cell, wherein the first epitaxial layer comprises a first tunnel junction, an InGaP sub-cell and a GaAs ohmic contact layer which are sequentially arranged in the direction away from the GaAs sub-cell; and the second epitaxial layer comprises a second tunnel junction, a gradient transition layer, an InGaAs sub-cell and an InGaAs ohmic contact layer which are sequentially arranged in a direction far away from the GaAs sub-cell. According to the solar cell , the current density matchin