Multi-junction (MJ) solar cells are solar cells with multiple p–n junctions made of different semiconductor materials. Each material's p–n junction will produce electric current in response to different wavelengths of light.
Schematic diagram of multi-junction tandem solar cells. The multi-junction solar cell (MJSC) consists of multiple p–n junctions of different semiconductor materials. These semiconductor materials absorb a wide range of wavelengths and improve electrical energy conversion efficiency .
These days, multi-junction solar cell with silicon as a bottom cell is giving the contemporary structure in industries. The high efficiencies and great performance in multi-junction arrangements are achieved by using III–V semiconductor materials .
In initial researches, the monolithically layered multi-junction solar cells have been studied, where the junction of germanium is achieved by diffusion of arsenide by layer produced by metal organic chemical vapor deposition from gallium arsenide.
The largest efficiency of about 43.49% is calculated for photovoltaic cells presented by solar cells of multiple junctions. Multi-junction solar cells are generally affected through a spectral bandwidth as compared to silicon . However, these solar cells are mostly demanding for semiconductors and exhibit anti-reflection coating designs.
For non-concentrating solar cells, the Si-based multi-junction provides better path to exceed the efficiency limit to 30%. The use of gallium arsenide (GaAs) and germanium materials is going less. The Si-based method can be done with fewer amounts and is less costly.