Tin Selenide Molecular Precursor for the Solution Processing of Thermoelectric Materials and Devices

Abstract

In the present work, we report a solution-based strategy to produce crystallographically textured SnSe bulk nanomaterials and printed layers with optimized thermoelectric performance in the direction normal to the substrate. Our strategy is based on the formulation of a molecular ink that can be continuously decomposed to produce a SnSe powder or printed into predefined patterns. The ink formulation and decomposition conditions are optimized to produce pure phase SnSe. The printed layer and the bulk material obtained after hot press display a clear preferential orientation of the crystallographic domains, with the a crystal direction parallel to the pressure axis and normal to the substrate. Such textured nanomaterials present highly anisotropic properties, with best thermoelectric performance in plane, i.e. in the directions parallel to the substrate, which coincide with the crystallographic bc plane of SnSe. This is an unfortunate characteristic because thermoelectric devices are designed to create/harvest temperature gradients in the direction normal to the substrate. We demonstrate that this limitation can be overcome with the introduction of small amounts of tellurium in the precursor ink. The presence of tellurium allows reducing the band gap, increase both charge carrier concentration and mobility, especially cross plane, with a minimal decrease of the Seebeck coefficient. These effects translate into record out of plane ZT values at 800 K.

Biomimetic Approach to Facilitate the High Filler Content in Free-Standing and Flexible Thermoelectric Polymer Composite Films Based on PVDF and Ag2Se Nanowires

“…Thermoelectric (thermoelectric) materials directly converting temperature gradient into electrical energy and vice versa are crucial in renewable energy conversion fields. − Applications including wearable devices and soft robotics have tremendously boosted the development of flexible TE materials, which can power electronics via harvesting heat from human body or environment and simultaneously can be applied on nonplanar surfaces. − Normally, the heat-to-electricity conversion efficiency of TE materials depends on the dimensionless figure of merit ZT (ZT = S 2 σ T /κ), where S (V K –1 ) represents the Seebeck coefficient, σ (S m –1 ) represents the electrical conductivity, T (K) is the absolute temperature, and κ is the thermal conductivity κ (W m –1 K –1 ) including the carrier transport (κ e ) and lattice thermal conductivity (κ L ). − Power factor (PF), which is defined as PF = S 2 σ, is another key parameter used to evaluate the TE performance. − Based on the types of charge carriers, TE materials can be classified into p-type and n-type. Thus far, the development of n-type flexible materials lags behind their p-type counterparts. − In addition, flexible TE materials in free-standing form are needed for comprehensively studying TE performance including the ZT value, as well as more suitable for developing wearable TE power generators to harness heat of curved surfaces and numerous emerging applications such as textile electronics, stretchable sensors, electrodes for electronic skin, and so forth. − Hence, novel flexible and free-standing n-type films with excellent TE performance are urgently needed.…”

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

“…As another approach, solution chemical synthesis can be used to prepare 2D semiconducting materials with a lot of benefits, including tunable reaction conditions and easy scale-up. Cabot and co-workers reported a chemical synthesis method using tin selenide molecular precursor under solution process to prepare 2D SnSe nanoplate for TE studies [ 199 ]. In the synthesis of 2D SnSe nanoplate, tin chloride selenium dioxide, tri-n-octylphosphine and oleyamine were premixed in a very short of time, followed by the addition of oleic acid to produce dentritic SnSe nanostructures.…”

Micro-Thermoelectric Generators: Material Synthesis, Device Fabrication, and Application Demonstration

“…To enhance the performance of the micro-TEG, high-performance thermoelectric materials and increasing the number of thermoelectric elements are vital factors. Regarding thermoelectric materials, until now, several thermoelectric materials have been studied, including organic materials (metalloporphyrin/single-walled carbon nanotube composite films [7], Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate [8], and compositions of conducting polymers and metal nanoparticles [9]) and inorganic materials (nanoporous silicon [10], cobalt triantimonide [11], bismuth telluride and antimony telluride [12], tin selenide [13], electrodeposited bismuth telluride [14]). Among them, thermoelectric-materials-based BiTe are widely investigated because of their high performance for applications at near room temperature.…”