Photovoltaic cell and manufacturing method thereof

A manufacturing method of a photovoltaic cell, comprising:

• providing a substrate comprising GaAs and having a first side and a second side opposite to the first side;
• forming a middle subcell having a second band gap, a base layer having a first type doping, and an emitter layer having a second type doping different from the first type doping and comprising a same material as that of the base layer, wherein the substrate is provided to be the base layer of the middle subcell, and the emitter layer is directly formed on the substrate;
• growing a top subcell comprising InGaP-based material and having a first band gap from the first side of the substrate;
• and
• growing a bottom subcell comprising InGaAs-based material and having a third band gap from the second side of the substrate,
• wherein the first band gap is larger than the second band gap, the second band gap is larger than the third band gap, the thickness of the middle subcell is at least 100 μm and the thickness of the top subcell or the bottom subcell is smaller than 10 μm, and the top subcell growing step is prior to the bottom subcell growing step.