Enhanced Thermoelectric Transport Properties of <i>n</i>-type InSe by Sn doping

Abstract

Layered post transition metal chalcogenides such as SnSe, SnSe&lt;sub&gt;2&lt;/sub&gt;, In&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt;, and In&lt;sub&gt;4&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; have attracted attention as promising thermoelectric materials due to their intrinsically low lattice thermal conductivities. Recently, &lt;i&gt;n&lt;/i&gt;-type indium selenide (InSe) based materials have also been suggested as good candidates for thermoelectric materials by optimizing their electrical properties, i.e., increasing carrier concentration. Here, we report enhancement of the thermoelectric properties of &lt;i&gt;n&lt;/i&gt;-type InSe by Sn substitutional doping at the In site. A series of In&lt;sub&gt;1-x&lt;/sub&gt;Sn&lt;sub&gt;x&lt;/sub&gt;Se for x = 0, 0.03, 0.05, 0.15 and 0.2 was examined. The carrier concentration and electrical conductivity increased due to the Sn substitution, since Sn behaves as a shallow electron donor in InSe, while the Seebeck coefficient decreased moderately. In addition, it was found that effective mass was increased by more than 10 times by Sn doping. As a result, the power factor was enhanced from 0.07 mW/mK&lt;sup&gt;2&lt;/sup&gt; to 0.13 mW/mK&lt;sup&gt;2&lt;/sup&gt; at 800 K. The total thermal conductivity was unchanged despite Sn doping because the electrical contribution to the total thermal conductivity was very small. Consequently, Sn doping in InSe enhanced the dimensionless thermoelectric figure of merit &lt;i&gt;zT&lt;/i&gt; from 0.04 to 0.14 at 800 K, mainly due to enhanced electrical properties.

Comparison of influence of intercalation and substitution of Cu on electrical and thermoelectric transport properties of InSe alloys

“…Among these materials, InSe has a high S in the range of 600-1000 mV K À1 and a k tot in the range of 1-4 W m À1 K À1 . [13][14][15] However, InSe has a band gap of B1.25 eV, which leads to a very low carrier concentration of 10 13 -10 14 cm À3 . 13,15,16 Thus, one strategy to improve the zT of InSe is doping to increase the carrier concentration.…”

“…[13][14][15] However, InSe has a band gap of B1.25 eV, which leads to a very low carrier concentration of 10 13 -10 14 cm À3 . 13,15,16 Thus, one strategy to improve the zT of InSe is doping to increase the carrier concentration. Choo et al reported that doping Sn in InSe increased the zT at 800 K to 0.14 by increasing the carrier concentration and electrical conductivity.…”

“…Choo et al reported that doping Sn in InSe increased the zT at 800 K to 0.14 by increasing the carrier concentration and electrical conductivity. 15 Lee et al employed Si dopants as a donor for InSe to favorably alter its electronic structure. 13 Lee et al used Cl doping in InSe to increase carrier concentration.…”

Unraveling the Mechanism of the Persistent Photoconductivity in InSe and its Doped Counterparts

“…Recently, high photoresponsivity, [ 16 ] photoconductivity, photovoltaic effect, [ 17 ] and thermoelectric effect [ 18 ] have been reported in InSe‐based photodetectors and phototransistors. Despite InSe as a benchmark 2D semiconductor having been researched widely, however, a detailed study of the PPC effect and relevant mechanism on the photoresponse of InSe‐based photodetectors is still not available.…”

Dynamic carrier transports and low thermal conductivity in n‐type layered InSe thermoelectrics

“…However, previous results found that InSe owns very low carrier concentration around ∼3.2 × 10 13 cm –3 at room temperature that largely restricts its thermoelectric performance. [ 22,23 ] Thus, both anion (Si and Sn) doping [ 22–25 ] and citation (Te) alloying [ 26 ] are conducted to optimize the carrier concentration in InSe, but the increase of carrier concentration is limited. Noticeably, the theoretical calculation results indicate that a maximum ZT of ∼0.65 can be achieved at 800 K with optimal carrier concentration.…”