this application is related to a method of manufacturing a solar cell device comprising providing a substrate comprising ge or gaas ; forming a first tunnel junction on the substrate , wherein the first tunnel junction comprises a first n - type layer comprising ingap : te , and a first alloy layer comprising alxgaas and having a lattice constant ; adding a material into the first alloy layer to change the lattice constant ; and forming a first p - n junction on the first tunnel junction .