Design and Spectral Performance of HfO2-Based Multilayer Spectrally Selective Emitters Embedded with VO2 Nanoparticles

In this study, HfO2-based multilayer spectrally selective emitters embedded with VO2 nanoparticles were designed and their spectral performance was analyzed. To verify the thermal stability of the designed emitters, in situ X-ray diffraction (XRD) was performed on the VO2 nanoparticles and the HfO2 film. The figure of merit (FOM), spectral selectivity efficiency (eta(s)), and spectral cutoff efficiency (eta(c)) were first adopted as the evaluation criteria, and an in-depth analysis of their relationship was conducted. Meanwhile, an ideal thermophotovoltaic (TPV) system was built to evaluate the spectral performance of the emitters that met the evaluation criteria requirements. Furthermore, the mechanism of the spectral selectivity of the proposed emitter was investigated. The in situ XRD results show that both the VO2 nanoparticles and HfO2 film can maintain thermal stability below 1300 K. The FOM is focused on the output energy of the emitter in the convertible waveband, while eta(s) and eta(c) are aimed at evaluating the energy conversion efficiency of the emitter. The emitters with maximum FOM, eta(s), and eta(c) show good performance in the TPV system. A trilayer emitter with a 100 nm embedded layer sandwiched by 10 nm HfO2 films can provide the TPV system with the highest conversion efficiency (13.4%) through the design process. The total thicknesses of the structures with good spectral performance are concentrated in the range of 90-165 nm. The structures can have good spectral performance in terms of their spectral emittance in the convertible waveband, which can be enhanced due to the influence of scattering of the nanoparticles. This study can provide guidelines for the development of a spectrally selective emitter with high thermal stability.