Balanced High Thermoelectric Performance in n-Type and p-Type CuAgSe Realized through Vacancy Manipulation

Abstract

As a liquid-like material, CuAgSe has high carrier mobility and ultralow lattice thermal conductivity. It undergoes an n–p conduction-type transition during β- to α-phase transition with increasing temperature. Moreover, optimization of the thermoelectric performance of CuAgSe is rather difficult, owing to the two-carrier conduction in this material. In this work, we reported the free tuning of the conduction type and thermoelectric performance of CuAgSe by manipulating the cation vacancies. Positron annihilation measurements reveal that the increase in CuAg content can effectively suppress the cation vacancies and reduce the hole carrier concentration, resulting in n-type conduction at high temperatures. Doping with Zn at the Cu sublattice in the CuAg-excessive CuAgSe can further decrease the number of vacancies, leading to a significant decrease in hole carrier concentration. Furthermore, the reduction of vacancies leads to weakening of carrier scattering. As a result, carrier mobility is also enhanced, thus improving the thermoelectric performance of n-type CuAgSe. On the other hand, high-performance p-type CuAgSe can be achieved by decreasing the CuAg content to introduce more cation vacancies. Ultimately, both n-type and p-type CuAgSe with superb thermoelectric performance are obtained, with a zT max of 0.84 in Cu1.01Ag1.02Zn0.01Se (n-type) and 1.05 in (CuAg)0.96Se (p-type) at 600 K and average zT of 0.77 and 0.94 between 470 and 630 K for n-type and p-type, respectively.

Flexible Ag2Se Thermoelectric Films Enable the Multifunctional Thermal Perception in Electronic Skins

“…Furthermore, the observed increase in n H depending on the increased thickness can result from the corresponding increased concentration of (SSe 2 ) 2– , which can suppress the Se vacancies, subsequently leading to the decrease in n H (see the experimental details in the Supporting Information). The increase in μ H offsets the negative effects of decreasing n H , subsequently leading to an increase in σ. The power factor (PF) values of the Ag 2 Se film with different thicknesses at 300 K were calculated following the equation PF = S 2 σ (Figure d), which are compatible with other high-performance TE materials, as shown in Figure e, ,,− and they exhibit potentials in fabricating wearable self-powered devices (Figures S4–S9).…”

Dual-Cation CuAgSe-Based Material: Rapid Mass Transfer in Synthesis and High Thermoelectric Performance Realization

“…Some exhibit a pronounced n-p type transition, while others show a decrease in the Seebeck coefficient without a clear n-p transition. Research findings indicate that cation vacancies are the key factor determining the conductivity type of CuAgSe . Therefore, by regulating the content of Ag ions and using the same preparation method mentioned above, we have synthesized CuAg 1+ x Se ( x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) thermoelectric materials, and synergistically optimized the electrical and thermal properties of CuAgSe (Figures S1–S3).…”

“…Thermoelectric properties of CuAg 1+ x Se ( x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05). (a) Electrical conductivity (σ); (b) Seebeck coefficient ( S ); (c) power factor (PF); (d) thermal conductivity (κ); (e) ZT value; (f) comparison of the maximum ZT value (ZT max ) and preparation time in this work with previously reported CuAgSe-based materials. ,,,,,, …”

“…Ultimately, the Ag-excess regulated CuAg 1+ x Se samples achieve significantly higher ZT values compared to the pristine sample across the entire temperature range, as depicted in Figure e. Notably, CuAg 1.04 Se achieves the highest ZT value of approximately 1.0 at 673 K, which is comparable to previously reported literature values (Figure f) …”

Cu2−xS and Cu2−xSe Alloys: Investigating the Influence of Ag, Zn, and Ni Doping on Structure and Transport Behavior

“…Selenides appear to be much more susceptible to doping with these elements, especially in the case of Ag-doped systems. Similar to sulfides, even a doped system typically coexists with other phases, and literature reports on restricting copper ion migration through silver remain contradictory [1,25,31,[43][44][45][46][47][48]. Ni and Zn also appear to be documented as dopants for Cu 2 Se; however, the available literature base in this case is quite limited [13,14].…”