Design of multijunction GaPNAs/Si heterostructure solar cells by computer simulation

The designs of two- and three-junction solar cells based on GaPNAs/Si lattice-matched hetero-structures are calculated. It is shown that the efficiency of two-junction solar cells constituted by a junction based on a GaPNAs solid solution with a band gap $E_g$ of 1.78 eV and a junction based on Si may reach a value of 30.3% under AM1.5 D, 100 mW/cm$^2$, and 35.4% under AM1.5D, 20 W/cm$^2$. The maximum values of the efficiency of the three-junction solar cell constituted by top and middle junctions based on GaPNAs with $E_g$ of 2 and 1.5 eV, respectively, and a Si-based bottom junction are 39.2% under AM1.5 D, 100 mW/cm$^2$, and 44.5% under AM1.5D, 20 W/cm$^2$. It is shown that the thickness and minority carrier lifetime of the photoactive layers affect the efficiency of solar-light conversion by the heterostructures being developed.