In this invention, the efficiency of a two-junction (cascade) tandem photovoltaic device is improved by adjusting (decreasing) the top cell thickness to achieve current matching. An example of the invention was fabricated out of Ga{sub 0.52}In{sub 0.48}P and GaAs. Additional lattice-matched systems to which the invention pertains include Al{sub x}Ga{sub l-x}/GaAs (x=0.3 {minus} 0.4), GaAs/Ge and Ga{sub y}In{sub 1-y}P/Ga{sub y+0.5}In{sub 0.5-{sub Y}} As (O<y<5).