A fundamental challenge in solar-thermal-electrical energy conversion is the thermal stability of nano-engineered materials and devices at high operational temperatures. Selective tungsten emitters based on 2-D photonic crystals have been found effective in controlling the motion of photons at certain wavelengths for thermophotovoltaic (TPV) systems. The nano-structured patterns, however, easily lose their structural integrity at high temperatures, which would disrupt the tight tolerances required for spectral control of the selective emitters. A novel idea of flat surface photonic crystal (FSPC) is developed to circumvent the surface diffusion at high temperatures. The key idea of FSPC is to make optically micro/nano structured but geometrically flat surface, which is fabricated by plugging the nanostructure with the IR-transparent ceramic. A silicon FSPC is tested at an equivalent homologous temperature to tungsten at 1200°C for hours and is observed to exhibit minimal physical and spectral degradation in contrast to the severe performance deterioration observed with a conventionally prepared 2D PhC. Combining this result with an Arrhenius accelerated lifetime model, an equivalent tungsten device is anticipated to survive over 40 years at >800°C, demonstrating a significant step toward feasible FSPC selective emitter design for commercial implementation of solar TPV.