We investigate the enhancements provided by a two dimensional hexagonal photonic crystal pattern and a back reflection layer on a gallium antimonide thermophotovoltaic cell. The photonic crystal pattern and back reflecting layers have been shown to increase the optical intensity within the active diode region, to increase the photon/exciton interaction time, and to decrease the number of recombination events. The end result is a TPV cell with a greater over all conversion efficiency, as well as, a larger external quantum efficiency and internal quantum efficiency. Thermophotovoltaic generators have traditionally been a three stage devices (emitter, filter, diode) which converts heat incident on the emitter (infrared photons) into a current out of the TPV cell. Present research in TPV devices demonstrate maximum conversion efficiencies of only around 20%. However, theory predictions that total system efficiencies of 30-40% can be reached. Our focus is on increasing the efficiency of the Gallium Antimonide (GaSb) TPV cell, a PN-photodiode through the use of a two dimensional photonic crystal cavity. A photonic crystal (PhC) is a periodic array of dielectric rods embedded in a different dielectric material. The periodic nature of a photonic crystal creates a photonic band diagram, and at specific wavelengths of light, a standing wave is generated within the PhC. The dimensions and geometries of a PhC can be changed in order to determine at which wavelength the standing wave occurs resulting in significant tunability. The resulting standing wave slowly leaks into the surrounding material, and has been found to increase detectivity in photodetectors. A photonic crystal cavity was first designed and optimized in Lumerical FDTD to create a PhC standing wave corresponding to the bandgap of GaSb. It was determined that the addition of both a back reflection layer and photonic crystal cavity increased the optical intensity within the active region of the TPV cell by 16% as well as increasing the photon/exciton interaction time by 223%. The PhC cavity was constructed in an ohmic contact to GaSb resulting in a decreased travel time for excitons and therefore a decreased number of potential recombination events. We also predict an increase in conversion efficiency from the low energy “filtering effect” of the PhC resulting in a much more effective TPV diode stage.