Thermophotovoltaic (TPV) cells that convert thermal heat directly into electricity are attracting attention as they potentially produce high output power densities. Owing to its capability to convert with a Carnot efficiency, an optimization of these cells is essential to further enhance their performance and efficiency. This paper focuses on the optimization of p-type emitter thickness of Gallium Antimonide (GaSb) based TPV cell using Silvaco TCAD simulation software. The simulation works in this paper were validated by having a good agreement with those from the experimental work in terms of the electrical characteristics and efficiency of the GaSb TPV cell. Further simulation was done with different p-type emitter thicknesses ranging from 0.15 μm to 1.20 μm, It was demonstrated that the open circuit voltage (Voc) of the cell increases while the short-circuit current density (Jsc) decreases with increasing p-type emitter thickness. Since the rate of increasing Voc is faster than that of decreasing Jsc, higher maximum power efficiency was obtained at an optimum thickness of 0.85 μm. It was found that, under AM1.5 illumination condition, an increment of power efficiency from 5.91 % to 6.63 % was achieved when increasing p-type emitter thickness from 0.15 μm to 0.85 μm.