GaSb photovoltaic (PV) cells with different designs for thermophotovoltaic generators were developed and investigated. Zn diffusion was used to form a p-n junction in n-GaSb substrates. Two diffusion technologies were studied: From the vapor and the liquid phase. Both diffusion technologies resulted in good PV cell parameters. However, diffusion from the vapor phase was found to be more simple and reproducible. The diffusion process parameters, which provide good control over Zn surface concentration and p-n junction depth, were determined. Photovoltaic parameters of the GaSb cells were measured under various illumination conditions and temperatures. The cell power output at maximum efficiency reached 952 mW for 1.89 cm2 cells. The developed cell fabrication technology have shown good reproducibility of cell parameters.