A Promising Selective Emitter Ho(Ta1− x Nb x )O4 with Enhanced Performance for Thermophotovoltaic Applications
Jingxuan Zheng, Xiaoping Zheng, Yafeng Shu, Yiwen Liu, Jitao Liu, Jianke Tian, Zhaocang Meng, Xue Zhang, Panli Qi, Juan Zhang, Canglong WangAbstract
Selective emitters with high spectral efficiency and structural stability are essential for efficient thermophotovoltaic systems. However, achieving simultaneous spectral matching and simplified fabrication remains a significant challenge. In this study, a series of selective emitters Ho(Ta1−xNbx)O4 were prepared via the straightforward solid-state reaction of Ho2O3 and Ta2O5. First-principles calculations were performed in order to further tune the electronic structure and optical bandgap of HoTaO4. Experimental results revealed that Nb5+ induced lattice distortion and symmetry reduction, effectively narrowing the bandgap and enhancing the Ho3+ 4f-4f electronic transitions. The optimized emitter exhibited a spectral efficiency of 47.59% at 1573 K, a peak power density of 9.65 W cm−2, and a figure of merit of 28.02% when paired with InGaAsSb cells (1.8−2.5 μm). Furthermore, the emitters demonstrated reduced thermal conductivity (3.74 W m−1 K−1) and suppressed grain growth (kp = 0.0451 μm2 h−1), ensuring excellent microstructural stability under extreme thermal conditions. This work provides a strategy for designing high-performance selective emitters for advanced energy conversion and industrial waste heat recovery.