Optimizing the average power factor of p-type (Na, Ag) co-doped polycrystalline SnSe

Abstract

Despite the achievable high thermoelectric properties in SnSe single crystals, the poor mechanical properties and the relatively high cost of synthesis restrict the large scale commercial application of SnSe. Herein, we reported that co-doping with Na and Ag effectively improves the thermoelectric properties of polycrystalline SnSe. Temperature-dependent carrier mobility indicates that the grain boundary scattering is the dominant scattering mechanism near room temperature, giving rise to low electrical conductivity for the polycrystalline SnSe in comparison with that of the single crystal. Co-doping with Na and Ag improves the electrical conductivity of polycrystalline SnSe with a maximum value of 90.1 S cm À1 at 323 K in Na 0.005 Ag 0.015 Sn 0.98 Se, and the electrical conductivity of the (Na, Ag) co-doped samples is higher than that of the single doped samples over the whole temperature range (300-773 K). Considering the relatively high Seebeck coefficient of 335 mV K À1 at 673 K and the minimum thermal conductivity of 0.48 W m À1 K À1 at 773 K, Na 0.005 Ag 0.015 Sn 0.98 Se is observed to have the highest PF and ZT among the series of samples, with values of 0.50 mW cm À1 K À2 and 0.81 at 773 K, respectively. Its average PF and ZT are 0.43 mW cm À1 K À2 and 0.37, which is 92% and 68% higher than that of Na 0.02 Sn 0.98 Se, 40% and 43% higher than that of Ag 0.02 Sn 0.98 Se, and 304% and 277% higher than that of the previously reported SnSe, respectively.

Tin-selenide as a futuristic material: properties and applications

“…There was a meager improvement in thermal conductivity, resulting in a ZT of 0.7. 109 There is a vast literature on doping in the polycrystalline SnSe, like Na, 110 K, 111 Cd, 112 Ag, 113 and co-doping Na/Ag, 114,115 Bi/Cl, 116 Na/CNT, 117 etc. which resulted in the enhancement in the thermoelectric performance of the material.…”

High‐Performance Thermoelectric SnSe: Aqueous Synthesis, Innovations, and Challenges

“…Among the state‐of‐the‐art thermoelectric materials, tin selenide (SnSe) is one of the most promising candidates to apply to thermoelectric devices due to its environmentally friendly feature, high cost‐effectiveness, and outstanding thermoelectric performance derived from its appropriate bandgap of ≈0.9 eV and intrinsic low κ l 9,10 . Figure a shows the development timeline for all SnSe‐based bulk thermoelectric materials,11–124 from which a record high ZT of ≈2.8 at 773 K was found in the n‐type SnSe single crystal,11 derived from its ultralow κ l of ≈0.18 W m −1 K −1 and high S 2 σ of ≈9.0 µW cm −1 K −2 at this temperature 125. Such a high ZT is also very competitive to other state‐of‐the‐art thermoelectric systems which possess ZTs > 2, such as PbTe,126–134 GeTe,135–147 Cu 2 Se/Cu 2 S,148–157 and AgSbTe 2 158.…”

“…A summary of ZTs for SnSe‐based thermoelectric materials. a) The timeline for state‐of‐the‐art SnSe bulks thermoelectric materials,11–124,169–182 the performance achieved by solution route are circled by yellow. b) Temperature‐dependent ZT and c) corresponding peak and average ZT values for polycrystalline SnSe through different fabrication techniques 13,16,22,46,58,62,95,99,101.…”

General strategies to improve thermoelectric performance with an emphasis on tin and germanium chalcogenides as thermoelectric materials

“…Co-doping of p-type polycrystalline SnSe with Na and Ag also effectively enhances the TE performance of SnSe. Wang et al 294 prepared Na 0.02− x Ag x Sn 0.98 Se ( x = 0, 0.005, 0.01, 0.015, and 0.02) class of samples via melting, annealing, and SPS methods. Carrier concentration was weakly temperature-dependent, and at room temperature, it reached a maximum of ∼2.66 × 10 19 cm −3 for x = 0.005.…”