Tin selenide 'nanoflakes' for miniature thermoelectric devices

March 29, 2018 // By Nick Flaherty
Researchers from Case Western Reserve University in Cleveland, Ohio, are investigating single crystal 'nanoflakes' of tin selenide (SnSe) for miniature thermoelectric devices that can generate power from temperature differences and be used for cooling.

2D materials such as graphene have been a focus for thermoelectric designs, and SnSe shows similar properties. "Our lab has been working on two-dimensional semiconductors with layered structures similar to graphene," said Xuan Gao, an associate professor at Case Western.

he group is looking at how the temperature difference across a material can cause charge carriers -- electrons or holes -- to redistribute and generate a voltage across the material, converting thermal energy into power.

"Applying a voltage on a thermoelectric material can also lead to a temperature gradient, which means you can use thermoelectric materials for cooling," said Gao. "Generally, materials with a high figure of merit have high electrical conductivity, a high Seebeck coefficient -- generated voltage per Kelvin of temperature difference within a material -- and low thermal conductivity," he said.

A thermoelectric figure of merit, ZT, indicates how efficiently a material converts thermal energy to electrical energy. The group's work focuses on the power factor, which is proportional to ZT and indicates a material's ability to convert energy.

The SnSe nanostructures are grown with chemical vapor deposition (CVD), evaporating a tin selenide powder source inside an evacuated quartz tube. Tin and selenium atoms react on a silicon or mica growth wafer placed at the low-temperature zone of the quartz tube, creating SnSe nanoflakes on the surface of the wafer. Adding a dopant element like silver to SnSe thin films during material synthesis can further optimize its thermoelectric properties.

At the start, "the nanostructure SnSe thin films we fabricated had a power factor of only around 5 percent of that of single crystal SnSe at room temperature," said researcher Shuhao Liu. Silver was the most effective dopant, resulting in a 300 percent power factor improvement compared to undoped samples, he said. "The silver-doped SnSe nanostructured thin film holds promise for a high figure of merit."

Vous êtes certain ?

Si vous désactivez les cookies, vous ne pouvez plus naviguer sur le site.

Vous allez être rediriger vers Google.