Core-shell structure selective emitter doped with rare earth elements for solar thermophotovoltaic system

Aiming at the low utilization of radiation photons in the solar thermophotovoltaic system, a rare earth core-shell (REC) structure selective thermal emitter is designed to achieve selective emission. The 3D symmetrical opal core-shell structure and rare earth elements play an important role in the selective emission characteristic of the REC emitter. The opal core-shell structure of the REC emitter is optimized by finite difference time domain simulation and numerical calculation, and the optimal size is determined. The REC emitter can adjust the characteristic peak of rare earth elements to produce a narrow-band radiation peak with an emissivity approaching 1 at a wavelength just before the cutoff wavelength, and maintain low emissivity in the long and short-wave bands. The conversion efficiency of the solar thermophotovoltaic system based on the REC emitter and InGaAs cell is 17.29 % at 1400 K, and the power density can reach 428.3 mW/cm2. The mechanism of the selective emission characteristic of the REC emitter is revealed, and its emissivity is insensitive to polarization and incidence angle. The REC emitter further improves the selective emission characteristic and makes the ra-diation spectrum better match the thermophotovoltaic cell. The power density and conversion efficiency of the solar thermophotovoltaic system are increased by improving the utilization of the thermophotovoltaic cell to the radiation photon.