Super low work function of alkali-metal-adsorbed transition metal dichalcogenides.

摘要: Discovering the materials that have work functions less than 1 eV is essential for efficient thermionic energy converter (TEC). The lowest function of reported so far in a range about eV. Here, to design low materials, we perform first-principles calculations on selected transition metal dichalcogenide as substrates and alkali metals adsorbates. our has dip ubiquitously independent true binding distances adsorbates exhibits contrasting behavior between empty d-shell elements (K, Rb, Cs) others (Li Na). We show interaction d-orbitals lone pair electrons chalcogen key function. From calculated parameters determine function, find that, regardless amount charge transfer, K WTe2 induces largest surface dipole moment, which consequently makes small 0.8 eV, smallest date, lowered further 0.7 by lattice strains. demonstrate thermal efficiency TEC using material exceeds thermoelectric with figure merit 5–10 temperature 880–1200 K.