AlGaAs solar cells grown by liquid phase epitaxy for dual junction solar cells based on c-Si bottom sub-cell

We report the growth of AlGaAs solar cells with bandgap energy of ~1.75eV by liquid phase epitaxy (LPE). Hall effect studies were first performed on AlGaAs epilayers in order to understand the relationship between carrier concentrations and dopant concentrations in melt. The dopants in this study include Sn, Te, Ge and Zn. Activation energies of these dopants were characterized, and we discovered that Sn forms DX centers in 1.77eV AlGaAs while Te does not. Based on the Hall effect results, AlGaAs solar cells were fabricated using two approaches: 1) sequential growth of the base, emitter and window layer; and 2) growth of an n-AlGaAs base followed by diffusion of p-type dopants from a high-Al concentration melt to form the emitter and the window layer simultaneously.