Effect of isotope on the near-field thermophotovoltaics

Isotope engineering, which has received much attention for significantly reducing the optical loss of phonon polaritons, opens new doors for thermal radiation manipulation. Recent studies have shown that the shift and broadening of phonon lines caused by isotopic mass effects significantly affect near-field radiative heat transfer. Near-field thermophotovoltaics (NF-TPV) is an efficient thermal-electric energy conversion device based on radiative heat transfer at the nano/micro scale. However, the impact of isotopes on NF-TPV remains to be further studied. Here, we have theoretically studied the performance of NF-TPV systems with hBN thermal emitters of distinct isotope compositions. The numerical results show that the 98.7% 10B hBN isotope enrichment configuration reaches 67.8 kW/m2 output power and 34.7% efficiency when the emitter temperature is 900 K, surpassing the natural hBN by 8.3 kW/m2 and 1.20%. Nevertheless, the performance is suppressed in 99.2% 11B hBN structure, reduced by 1.8 kW/m2 and 0.64% compared to natural hBN. This is attributed to the isotope-induced shift and broadening of the region of hyperbolic phonon polaritons. This study can provide theoretical guidance for designing NF-TPV systems based on isotope engineering and has great application prospects in renewable energy and energy storage fields.