Radioisotope thermophotovoltaic (RTPV) system show great potential for military and space application due to scalable, independent and high density energy characteristics. RTPV systems convert radioisotope decay thermal energy into electricity via thermally radiating photons. They are scalable for various applications, and have the potential to significantly enhance the photovoltaic conversion efficiency by tailoring the radiative spectrum to match to the band gap of PV diodes. We develop a high fidelity RTPV model that incorporates various non-idealities. The radiative spectra of emitters surfaces are engineered a photonic crystals (PhCs) which have periodic structure. Based on the model prediction, we aim to realize high efficiency RTPV energy conversion systems.