“…Besides, the normalized phonon density of states (PDoS) of Cu 2 Se and B 4 C only [50,51] h) ZT values and i) Comparison of the maximum ZT value in this work with the highest value reported in previous studies. [14][15][16][17]19,46,47,[53][54][55][56][57][58][59][60][61][62] shows minimal overlaps (Figure 4g), [50,51] indicating huge interfacial thermal resistance at higher frequencies. This dramatically low 𝜅 l could be also related to the weak electron-phonon coupling induced by nano-sized secondary phases, as reported by Wu et al [52] Consequently, by incorporating 0.9 vol.% B 4 C into the Cu 1.99 Se matrix, a high PF can be achieved without sacrificing too much 𝜅, resulting in a maximum ZT of 2.6 at 1025 K (Figure 4h), supported by the good repeatability and reproducibility of our experimental results (Figures S18,S19, Supporting Information).…”