In recent years, with some new effects and new mechanisms of thermoelectric transport proposed and developed, many new high-performance thermoelectric material systems have also been discovered, of which, diamond-like structural compounds derived from the diamond structure, due to the atomic elements Due to the different radius and chemical valence, the crystal lattice of the material is distorted from the cubic structure of diamond to the non-cubic structure, and the inherent low thermal conductivity and the adjustable electrical property of the diamond-like structure compound make it be an excellent thermoelectric material. Since 2009, the Shanghai Institute of Ceramics, Chinese Academy of Sciences thermoelectric research team for the first time reported quaternary compounds Cu 2CdSnSe 4And Cu 2ZnSnSe 4Of diamond-like compounds have attracted much attention in the field of thermoelectric research.So far, more than 20 types of diamond-structured compounds have been reported, of which the pyroelectric properties of various p-type materials are above 1, However, the thermoelectric figure-of merit of n-type diamond-like compounds is generally low, which limits the development of efficient diamond-like structure compound thermoelectric devices.
Recently, an associate researcher at the Shanghai Silicate Institute, Chou Pengfei, researcher Shi Xun and Chen Lidong, together with Yang Jiong, a professor from Shanghai University, discovered a high-performance n-type type with intrinsically low lattice thermal conductivity and electrical properties Diamond Structure Compound AgInSe 2At 900K, AgInSe 2The highest thermoelectric yield of the base compound reached 1.1, the best CuGaTe reported so far 2, CuInTe 2And other p-type diamond-like structural compounds.On the basis of this, the research team for the first time to prepare a display of good prospects for application of diamond-like compounds thermoelectric components.
The bandgap of AgInSe2 is about 1.2eV, and the previous research on AgInSe2 mainly focuses on the field of optoelectronics.It was found that AgInSe2has a much lower lattice thermal conductivity than other diamond-like structural compounds.At room temperature, AgInSe 2Of the lattice thermal conductivity of only 0.99W m-1K-1, and amorphous glass equivalent first-principles calculations show that, AgInSe 2Phonon spectra of the existence of a large number of low-frequency optical branch, strong scattering and its frequency close to the lattice phonon, is leading to AgInSe 2The fundamental reason of low lattice thermal conductivity. Further study found that these low-frequency optical branch from the 'Ag-Se cluster' synergistic vibration in AgInSe 2In the crystal structure, Ag and Se are bound by strong chemical bonds, and In and the chemical bonds of the two atoms are weak. Therefore, Ag and Se can form 'Ag-Se cluster' with larger total mass, The binding force is weak, and thus shows low phonon vibration frequency on the other hand, by the AgInSe 2In the introduction of Se vacancies or the introduction of Ag element Ag doping, conductivity can be achieved orders of magnitude increase.Preliminary studies have shown that, with a small amount of Se vacancy AgInSe 2The thermoelectric figure of merit reached 1.1 at 900K.
Based on high performance n-type AgInSe 2Compounds and the research team previously reported p-type CuInTe 2Based compound (J. Mater. Chem. A, 2016, 4, 1277), the study for the first time prepared with two pairs of thermoelectric single-couple structure of diamond-like compound thermoelectric devices using plating and brazing technology, the successful single thermoelectric single The cold junction and the hot junction are respectively connected to the Ni electrode and the Mo-Cu electrode.The preliminary test results show that the maximum output power of the device is 0.06W at 520K temperature difference.If the contact resistance and the contact thermal resistance at the device interface can be further optimized, Its performance will be further enhanced.
Relevant research results have been published in Advanced Science, which is funded by the National Natural Science Foundation of China, key deployment projects of the Chinese Academy of Sciences, the Youth Innovation Promotion Association and the Shanghai Excellent Subject Leader Program.
Figure 1. (a) Thermoelectric figure of merit for n-type AgInSe2 diamond-like compounds; (b) First diamond-like structure compound thermoelectric device
Figure 2. (a) Phonon spectrum of n-type AgInSe2 diamond-like structure compound; (b) lattice thermal conductivity
