Thermoelectric devices based on thermoelectric materials, which can be utilized to transform heat to electric energy, are regarded as the clean and reliable energy-harvestings that reduce greenhouse gas and noxious gas missions. In this work, thermoelectric properties of square-Ag₂X (X = S, Se) monolayers have been systematically studied through uniting Boltzmann transport theory and first-principles. The results show that square-Ag₂X (X = S, Se) monolayers possess ultrahigh electrical conductivities due to their ultralight electron effective masses, together with high Seebeck coefficients, resulting in ultrahigh power factors (0.014 and 0.018 W/m K²). Moreover, phonon transport calculations unveil that square-Ag₂X (X = S, Se) monolayers exhibit low lattice thermal conductivities (3.46 and 2.33 W/m K) at 300 K, which can be traced back to their small Debye temperature, low acoustic group velocities, short phonon relaxation times and large Grüneisen parameters. Accordingly, the obtained figure of merit of monolayer square-Ag₂Se for optimal n-type doping at 700 K can approach 2.81, which is larger than the well-known n-type thermoelectric monolayer SnSe (2.32) and Mg₃Sb₂ (2.21). Therefore, the excellent thermoelectric properties of square-Ag₂Se monolayer along with its all-round stability verified by the phonon dispersion, ab initio molecular dynamic simulation and accordance of Born–Huang criteria highlight its prominent potential for thermoelectric applications.

基于热电材料的热电设备可用于将热量转换为电能，被认为是清洁可靠的能源收集方式，可减少温室气体和有害气体的排放。在这项工作中，已经通过结合玻耳兹曼输运理论和第一性原理系统地研究了方形Ag ₂ X（X = S，Se）单层的热电性质。结果表明，方形Ag ₂ X（X = S，Se）单层膜由于具有超轻的电子有效质量而具有超高的电导率，并且具有高的塞贝克系数，从而产生了超高的功率因数（0.014和0.018 W / m K ²）。 。而且，声子传输计算揭示了Ag _2的平方X（X = S，Se）单层在300 K时表现出较低的晶格热导率（3.46和2.33 W / m K），这可以追溯到其小的德拜温度，低的声团速度，短的声子弛豫时间和较大的Grüneisen参数。因此，在700 K时获得最佳n型掺杂的单层方形Ag ₂ Se的品质因数可以达到2.81，这比众所周知的n型热电单层SnSe（2.32）和Mg ₃ Sb ₂（ 2.21）。因此，方型Ag ₂ Se单层的优异热电性能以及通过声子分散，从头开始验证的全方位稳定性 分子动力学模拟和Born-Huang标准的遵循突出了其在热电应用中的巨大潜力。